Younger hepatocellular carcinoma patients have better prognosis after percutaneous radiofrequency ablation therapy.

Abstract

To evaluate the impact of age on the prognosis of patients with hepatocellular carcinoma (HCC) undergoing percutaneous radiofrequency ablation (RFA).
Whether age plays an important role in the outcomes of HCC after RFA remains controversial.
Two hundred fifty-eight consecutive treatment naive HCC patients who underwent RFA were enrolled. Patients aged ≤ 65 years (n = 100) were defined as the younger group and those aged > 65 years (n = 158) were the elderly group. Their clinicopathologic features and prognosis were compared.
Younger patients had a higher male-to-female ratio, higher prevalence of hepatitis B virus, and smaller tumor size than elder patients. After median follow-up of 28.5 ± 18.7 months, 45 patients died. The cumulative 5-year survival rates were 81.3% and 65.4% in younger and elder HCC patients, respectively (P = 0.008). Multivariate analysis disclosed that age > 65 years, serum albumin level ≤ 3.7 g/dL, prothrombin time international normalized ratio > 1.1, α-fetoprotein (AFP) > 20 ng/mL, and no antiviral therapy after RFA were independent risk factors associated with poor overall survival. Besides, there were 163 patients with tumor recurrence after RFA. Multivariate analysis showed that age > 65 years, platelet count ≤ 10/mm, AFP > 20 ng/mL, multinodularity, and tumor size > 2 cm were the independent risk factors predicting recurrence.
Both liver functional reserve (serum albumin level, prothrombin time international normalized ratio, platelet count, and antiviral therapy) and tumor factors (tumor size, number, and AFP level) were crucial in determining post-RFA prognosis in HCC patients. Moreover, younger HCC patients have better overall survival and lower recurrence rate after RFA compared with elder patients.

Full text

Page 1

Younger Hepatocellular Carcinoma Patients
Have Better Prognosis After Percutaneous
Radiofrequency Ablation Therapy
Wei-Yu Kao, MD,* Yi-You Chiou, MD,wz Hung-Hsu Hung, MD,*z Chien-Wei Su, MD,*zy
Yi-Hong Chou, MD,wz Teh-Ia Huo, MD,*8 Yi-Hsiang Huang, MD, PhD,*y Wen-Chieh Wu, MD,*
Han-Chieh Lin, MD,*z Shou-Dong Lee, MD,*z and Jaw-Ching Wu, MD, PhDyz
Goals: To evaluate the impact of age on the prognosis of patients
with hepatocellular carcinoma (HCC) undergoing percutaneous
radiofrequency ablation (RFA).
Background: Whether age plays an important role in the outcomes
of HCC after RFA remains controversial.
Study: Two hundred fifty-eight consecutive treatment naive HCC
patients who underwent RFA were enrolled. Patients aged r65
years (n=100) were defined as the younger group and those aged
>65 years (n=158) were the elderly group. Their clinicopatho-
logic features and prognosis were compared.
Results: Younger patients had a higher male-to-female ratio, higher
prevalence of hepatitis B virus, and smaller tumor size than elder
patients. After median follow-up of 28.5±18.7 months, 45
patients died. The cumulative 5-year survival rates were 81.3%
and 65.4% in younger and elder HCC patients, respectively
(P=0.008). Multivariate analysis disclosed that age >65 years,
serum albumin level r3.7g/dL, prothrombin time international
normalized ratio >1.1, a-fetoprotein (AFP) >20ng/mL, and no
antiviral therapy after RFA were independent risk factors
associated with poor overall survival. Besides, there were 163
patients with tumor recurrence after RFA. Multivariate analysis
showed that age >65 years, platelet count r105/mm3, AFP
>20ng/mL, multinodularity, and tumor size >2cm were the
independent risk factors predicting recurrence.
Conclusions: Both liver functional reserve (serum albumin level, pro-
thrombin time international normalized ratio, platelet count, and
antiviral therapy) and tumor factors (tumor size, number, and AFP
level) were crucial in determining post-RFA prognosis in HCC
patients. Moreover, younger HCC patients have better overall survi-
val and lower recurrence rate after RFA compared with elder patients.
Key Words: age, hepatocellular carcinoma, prognosis, radio-
frequency ablation
(J Clin Gastroenterol 2012;46:62–70)
H
liver transplantation and resection surgery are currently
regarded as the optimal treatment modalities for patients
with small HCC, they are often infeasible due to the
scarcity of liver transplantation donors or the relatively
poor liver functional reserve of the patients that makes
resection surgery impossible.4Local ablation therapies have
been introduced for patients with small HCC not eligible
for surgery in the recent decades.5,6Among local ablation
therapies, percutaneous radiofrequency ablation (RFA) is
superior due to fewer therapy sessions, better local tumor
control, and higher survival rates.7–9Consequently, RFA is
widely applied as a first-line therapy for patients with small
HCC who could not receive surgical resection or liver
transplantation in the recent years.10–15
Whether or not age plays an important role in the
outcomes of HCC remains controversial.16–21
studies demonstrate that younger and elder HCC patients
have comparable prognosis. Another study shows that
younger patients have better long-term outcomes due to
their better liver functional reserves. However, other studies
reveal that younger patients tend to present with advanced
tumor stages at the time of diagnosis, thereby leading to
poorer prognosis.22,23
The discrepancies among these
studies may be due to the diverse demographic character-
istics, extrahepatic comorbidities, clinicopathologic fea-
tures, and treatment modalities of the study patients.
For patients with small HCC who undergo RFA, there
is paucity of data on the impact of age on clinicopathologic
features and long-term outcomes. This study aimed to com-
pare the prognosis between younger and elder HCC
patients who underwent RFA and to identify factors that
affect these outcomes.
epatocellular carcinoma (HCC) is one of the leading
causes of cancer mortality worldwide.1–3Although
Several
MATERIALS AND METHODS
Patients and Follow-up
This cohort study retrospectively reviewed HCC patients
who were infeasible or refused to receive resection surgery or
Received for publication March 4, 2011; accepted June 27, 2011.
From the *Division of Gastroenterology, Department of Medicine;
wDepartment of Radiology; zDepartment of Medical Research and
Education, Taipei Veterans General Hospital, Taipei, Taiwan;
zFaculty of Medicine; yInstitute of Clinical Medicine; and
8Institute of Pharmacology, School of Medicine, National Yang-
Ming University, Taipei, Taiwan.
Grant Support: This study was supported by grants from the National
Science Council (97-2314-B-075-035, 98-2314-B-075-030-MY2),
Taiwan and Taipei Veterans General Hospital (V95C1-014,
V97A-033, V98A-072, V97B1-015, V98C1-120, Center of Excel-
lence for Cancer Research at TVGH (DOH100-TD-C-111-007),
Taipei, Taiwan.
Disclosures: There is no potential conflict of interest involved in this
study. A part of this study has been shown as a poster presentation
at the 21st Conference of the Asian Pacific Association for the
Study of the Liver (APASL 2011), 17–20 February 2011, QSNCC,
Bangkok, Thailand.
Reprints: Yi-You Chiou, MD, Division of Gastrointestinal Radiology,
Department of Radiology, Taipei Veterans General Hospital; 201
Shih-Pai Road, Sec. 2, Taipei 112, Taiwan (e-mail: yychiou@vghtpe.
gov.tw) or
Chien-Wei Su, MD, Division of Gastroenterology, Department of
Medicine, Taipei Veterans General Hospital; 201 Shih-Pai Road,
Sec. 2, Taipei 112, Taiwan (e-mail: cwsu2@vghtpe.gov.tw).
Copyrightr2012 by Lippincott Williams & Wilkins
ORIGINAL ARTICLE
62|www.jcge.comJ Clin Gastroenterol?Volume 46, Number 1, January 2012

Page 2

liver transplantation and underwent RFA in Taipei Veterans
General Hospital from January 1, 2002 to December 31,
2008. The choice of RFA was decided by the patients after
the physicians explained the advantage, side effects, and
prognosis among the various therapy modalities including
resection surgery, liver transplantation, local ablation ther-
apy, transarterial chemoembolization, and chemotherapy.
After review of medical chart records, a total of
258 consecutive treatment-naive HCC patients who fulfilled
the diagnostic criteria of HCC by the American Association
for the Study of Liver Disease (AASLD consensus, 2010)5
and underwent RFA as their first treatment modality
were enrolled for analysis. In our cohort, 165 patients refused
surgical intervention, 90 patients were ineligible for resection
due to portal hypertension or jaundice, and the remaining 3
patients were not suitable for resection due to tumor location.
The inclusion criteria were tumor size <5cm without
extrahepatic metastasis; the number of tumor was 3 or less;
grade A or B Child Pugh classification of liver function; and
no major comorbidities that might complicate RFA. The
institutional review board approved the study, which
complied with standards of the Declaration of Helsinki and
current ethical guidelines.
The cohort used 2 different RFA devices: the Cool-Tip
Radiofrequency System (Radionics, Burlington, MA) for
238 patients and the Radiofrequency Interstitial Tissue
Ablation device (Rita Medical Systems, Mountain View,
CA) for the remaining 20 patients. With the Cool-Tip
device, treatment was performed with a single (2-cm or
3-cm active tip) needle electrode. Each tumor had 1 to 4
ablations per session depending on the tumor size.15With
the Radiofrequency Interstitial Tissue Ablation device,
ablation was with an expandable needle electrode (Star-
burst TM, 2 to 3cm; or Starburst XL, 3 to 5cm). RFA was
performed with real-time ultrasonography guidance and the
RF electrode was advanced into the tumor. After RFA, all
patients underwent immediate ultrasonography to check
for possible bleeding or fluid accumulation.
Dynamic computed tomography (CT) scan was done
1 month after all of the tumors were ablated by RFA.
Magnetic resonance imaging (MRI) was performed in
patients with allergy to the contrast medium of CT scan,
with renal insufficiency, or with inconclusive diagnosis of
CT scan. When residual tumors were confirmed, a second
session of RFA was conducted. Among the 258 patients,
223 patients were successfully treated with 1 RFA session
and the remaining 35 patients with 2 sessions.
If no viable tumor was detected, the patient was
followed-up with testing for serum liver biochemistries,
a-fetoprotein (AFP) levels, and ultrasonography every
3 months; and CT scan or MRI every 6 months until
January 31, 2010. The starting date of follow-up for tumor
recurrence was the day when all of the tumors ablated by
RFA were confirmed by CT scan or MRI. All patients were
followed-up until their last hospital visit or death.
Tumor recurrence was suspected if there was elevated
serum AFP level (>20ng/mL) or new lesions detected by
surveillance ultrasonography, and was confirmed and
diagnosed by dynamic CT or MRI. Local recurrence was
defined as tumor recurrence at the area or margin of a
previously treated tumor, whereas intrahepatic distant
recurrence was diagnosed when a new lesion occurred in
a different site of the previously treated tumors.
Biochemical and Serologic Markers
Serum hepatitis B surface antigen (HBsAg) was tested
usingradioimmunoassay (Abbott
Chicago, IL), whereas antibody to hepatitis C virus (HCV)
Laboratories, North
TABLE 1. Comparison of the Demographic Data of Between Younger (Age r65y) and Elder (Age >65y) HCC Patients
Parameter Total (n=258)Younger (n=100)Elder (n=158)P
Patient demographics
Age (y/o) (mean±SD)
Sex (M:F) (%)
Comorbidities (yes/no) (%)
Serum biochemistry tests and liver function tests
Albumin (g/dL) (median; 25 and 75 percentiles)*
Bilirubin (mg/dL) (median; 25 and 75 percentiles)*
ALT (U/L) (median; 25 and 75 percentiles)
AST (U/L) (median; 25 and 75 percentiles)
Creatinine (mg/dL) (median; 25 and 75 percentiles)
Alk-P (U/L) (median; 25 and 75 percentiles)*
PTINR (median; 25 and 75 percentiles)
Platelet (median; 25 and 75 percentiles)
Child-Pugh A/B
Viral factors
HBsAg (positive/negative)*
Anti-HCV (positive/negative)*
Antiviral agents (yes/no) *
Tumor factors
Tumor size (cm) (median; 25 and 75 percentiles)
Single/multinodularity (%)
AFP (ng/mL) (median; 25 and 75 percentiles)
Recurrence pattern
Local recurrence/ Intra-hepatic recurrence (%)
67.8±11.5
162/96 (62.8%/37.2%)
42/216 (16.3%/83.7%)
55.4±6.5
74/26 (74.0%/26.0%)
13/87 (13.0%/87.0%)
75.7±5.6
88/70 (55.7%/44.3%)
29/129 (18.4%/81.6%)
<0.001
0.005
0.336
3.9; 3.5-4.2
0.8; 0.5-1.2
51.0; 32.0-97.3
55.0; 35.0-90.5
1.0; 0.8-1.2
95.0; 75-128.0
1.0; 1.0-1.1
113500; 84000-160250
226/32 (87.6%/12.4%)
3.9; 3.6-4.3
0.8; 0.6-1.2
56.5; 36.0-102.8
54.5; 35.0-76.8
1.0; 0.8-1.1
96.0; 79.5-130.5
1.0; 1.0-1.1
105000; 70000-160750
89/11 (89.0%/11.0%)
3.8; 3.4-4.2
0.8; 0.5-1.2
48.0; 29.0-93.0
55.5; 35.0-101.0
1.0; 0.8-1.3
93.0; 68.0-125.8
1.0; 1.0-1.1
118500; 92750-159500
137/21 (86.7%/13.3%)
0.074
0.354
0.092
0.262
0.521
0.185
0.565
0.141
0.726
108/144 (42.9%/57.1%)
121/133 (47.6%/52.4%)
38/215 (15.0%/85.0%)
52/45 (53.6%/46.4%)
44/55 (44.4%/55.6%)
26/71 (26.8%/73.2%)
56/99 (38.9%/61.1%)
77/78 (49.7%/50.1%)
12/144 (7.7%/92.3%)
0.009
0.493
<0.001
2.2; 1.6-2.9
212/46 (80.5%/19.5%)
19.1; 7.7-60.2
2.0; 1.5-2.6
85/15 (85.0%/15.0%)
19.6; 7.3-51.7
2.5; 1.8-3.0 0.001
0.437
0.688
127/31 (80.4%/19.6%)
18.1; 7.7-89.6
89/74 (54.6%/45.4%)27/28 (49.1%/50.9%)62/46 (57.4%/42.6%)0.400
P indicates comparison between younger and elder patients. AFP indicates a-fetoprotein; ALT, alanine aminotransferase; Alk-P, alkaline phosphatase;
AST, aspartate aminotransferase; HBsAg, hepatitis B surface antigen; HCC, hepatocellular carcinoma; HCV, hepatitis C virus; PTINR, prothrombin time
international normalized ratio; RFA, radiofrequency ablation; SD, standard deviation.
*Showed that there had missing data at the time of radiofrequency ablation in this parameter.
J Clin Gastroenterol?Volume 46, Number 1, January 2012Age and RFA Prognosis
r2012 Lippincott Williams & Wilkinswww.jcge.com|63

Page 3

was measured by second-generation enzyme immunoassay
(Abbott Laboratories, North Chicago, IL). Serum biochem-
istries, including albumin, bilirubin, alanine aminotransferase,
aspartate aminotransferase, alkaline phosphatase, g-gluta-
myltransferase, blood urea nitrogen, creatinine, and glucose,
were measured using a systemic multi-auto-analyzer (Tech-
nicon SMAC, Technicon Instruments Corp., Tarrytown,
NY). Serum AFP level was measured by radioimmunoassay
(Serono Diagnostic SA, Coinsin/VD, Switzerland).
Statistical Analysis
Baseline characteristics to be evaluated with outcomes
were selected according to the European Association for the
Study of the Liver guidelines published in 2001.24Pearson
w2analysis or Fisher exact test were used to compare
categorical variables, whereas the Mann-Whitney U test
was used to compare continuous variables. Cumulative
recurrence rates or overall survival rates were estimated by
the Kaplan-Meier method and compared using Cox
proportional hazards model.
As the mean age of the cohort was 67.8 years and
World Health Organization defined age >65 years as the
elderly, this study stratified patients aged 65 years or less as
the younger group and those aged >65 years as the
elderly group.
Statistically significant (P<0.05) variables by univari-
ate analysis were subsequently submitted to multivariate
analysis using a Cox forward stepwise logistic regression
model. A 2-tailed P<0.05 was considered statistically
significant. All statistical analyses were performed using the
Statistical Package for Social Sciences (SPSS 17.0 for
Windows, SPSS. Inc., Chicago, IL).
RESULTS
Comparison of Clinical Demographic Data
Among the 258 patients, 23 patients had HCC
detected by abdominal ultrasonography and confirmed by
CT scan (or MRI) because of symptoms (including fever,
legs edema, or abdominal fullness), 195 patients were
diagnosed by surveillance of chronic hepatitis B or C, and
the remaining 40 patients were diagnosed on a physical
check up. The demographic characteristics of all enrolled
patients are shown in Table 1. The proportion of male
patients was significantly higher in the younger group
(74.0% vs. 55.7%, P=0.005) than that in the elderly
group. More patients in the younger group were chronic
hepatitis B virus (HBV) carriers (P=0.009). Regarding
liver functional reserve, younger patients had a trend of
having higher serum albumin (P=0.074) and alanine
aminotransferase (P=0.092) levels than elder patients.
Besides, 42 patients presented with extrahepatic comorbid-
ities, including accompanying with other cancers, coronary
artery disease, congestive heart failure, end stage renal
disease, and stroke. The incidence of comorbidities between
younger and elder patients were comparable statistically
(P=0.336). Besides, there were no age related differences
in management of liver disease, including endoscopic
screening and prophylaxis of variceal bleeding.
Considering tumor factors, younger patients had
smaller tumor sizes (P=0.001), but serum AFP levels
and the number of tumors were comparable between the
2 groups.
In this cohort, 38 patients received antiviral therapy
after RFA, including 9 patients with lamivudine, 10
patients with entecavir, and 19 patients with pegylated
interferon therapy. More patients in the younger group
received antiviral therapy after RFA than in the elderly
group (26.8% vs. 7.7%; P<0.001).
Factors Associated With Overall Survival
Stratified by Age and Prognostic Factors
After median follow-up of 28.5±18.7 months, 45
patients died and 213 were alive on their last visit. The
cause of death among the 10 younger HCC patients who
died were HCC in 5 patients (50%), liver failure or
esophageal varix bleeding in 3 patients (30%), and sepsis
in the remaining 2 patients (20%), respectively. Regarding
the 35 elder patients who died in the follow-up, 16 patients
died due to HCC (45.7%), 15 patients died due to liver
failure or esophageal varix bleeding (42.9%), and the
remaining 4 patients died due to sepsis (11.4%). The causes
of death were similar between younger and elder patients
(P=0.677).
FIGURE 1. A, Cumulative overall survival in hepatocellular
carcinoma (HCC) patients stratified by age. The cumulative
curves were plotted using the Kaplan-Meier method and
compared by log-rank test. Young patients had better overall
survival rate than elder patients (P=0.008). B, Cumulative
recurrence in HCC patients stratified by age. Young patients
had lower incidences of recurrence after RFA than did elder
patients (P=0.009).
Kao et alJ Clin Gastroenterol?Volume 46, Number 1, January 2012
64|www.jcge.com
r2012 Lippincott Williams & Wilkins

Page 4

The overall cumulative survival rates at 1, 2, 3, and
5 years of all patients were 95.8%, 88.2%, 79.0%,
and 71.3%, respectively. Stratified by age, the overall
cumulative survival rates at 1, 2, 3, and 5 years were 98.0%,
95.0%, 87.0%, and 81.3% in younger HCC patients and
93.9%, 83.1%, 72.4%, and 65.4% in the elder patients,
respectively. The overall survival rates were significantly
higher in younger HCC patients (P=0.008; Fig. 1A).
Univariate analysis showed that elder age (>65y),
female sex, lower serum albumin (r3.7g/dL) and higher
bilirubin (>1.6mg/dL) levels, lower platelet counts (<105/
mm3), higher prothrombin time international normalized
ratio (PTINR) (>1.1), elevated AFP (>20ng/mL) levels,
and no antiviral therapy after RFA were associated with
poor overall survival (Table 2).
In multivariate analysis, age >65 years [Hazard ratio
(HR), 2.415; 95% confidence interval (CI), 1.174-4.968;
P=0.017], serum albumin level r3.7g/dL (HR, 3.522;
95% CI, 1.794-6.915; P<0.001), PTINR >1.1 (HR, 2.495;
95% CI, 1.324-4.700; P=0.005), elevated AFP (>20ng/
mL) (HR, 2.285; 95% CI, 1.199-4.355; P=0.012), and no
antiviral therapy after RFA (HR, 7.383; 95% CI, 1.746-
31.212; P=0.007) were independent risk factors associated
with poor overall survival.
Factors Associated With Recurrence After RFA
After RFA, 163 patients had tumor recurrence, with
11.5±12.6 months median time of development. The
cumulative rate of recurrence at 1, 2, 3, and 5 years were
34.1%, 53.9%, 71.2%, and 79.8%, respectively. Stratified
TABLE 2. Factors Associated With Poor Overall Survival After RFA for HCC by Univariate and Multivariate Analysis
Univariate Analysis Multivariate Analysis
Variable
Age: >65/r65y/o
Sex: Female/male
HBsAg: positive/negative*
Anti-HCV: positive/negative*
Albumin: r3.7/>3.7g/dL*
Bilirubin: >1.6/r1.6mg/dL*
ALT: >40/r40U/L
AST: >45/r45U/L
Platelet: r105/>105/mm3
PTINR: >1.1/r1.1
AFP: >20/r20ng/mL
Multiple tumor (yes/no)
Tumor size: >2cm/r2cm
Creatinine: >1.5/r1.5mg/dL
Antiviral therapy (No/Yes)*
Case No.
Hazard Ratio (95%
Confidence Interval)P
Hazard Ratio (95%
Confidence Interval)P
158/100
96/162
108/144
121/133
92/146
26/229
161/97
149/109
101/157
59/199
126/132
46/212
149/109
21/237
215/38
2.513 (1.244-5.076)
2.210 (1.230-3.973)
1.001 (0.814-1.233)
1.076 (0.803-1.445)
4.620 (2.445-8.727)
2.579 (1.199-5.547)
1.382 (0.735-2.599)
1.767 (0.950-3.286)
2.692 (1.488-4.872)
3.442 (1.914-6.192)
2.513 (1.352-4.672)
1.531 (0.734-3.193)
1.491 (0.809-2.747)
2.236 (0.994-5.297)
4.569 (1.106-18.867)
0.008
0.008
0.990
0.623
<0.001
0.015
0.315
0.072
0.001
<0.001
0.004
0.256
0.200
0.067
0.036
2.415 (1.174-4.968) 0.017
3.522 (1.794-6.915)<0.001
2.495 (1.324-4.700)
2.285 (1.199-4.355)
0.005
0.012
7.383 (1.746-31.212)0.007
AFP indicates a-fetoprotein; ALT, alanine aminotransferase; AST, aspartate aminotransferase; HBsAg, hepatitis B surface antigen; HCC, hepatocellular
carcinoma; HCV, hepatitis C virus; PTINR, prothrombin time international normalized ratio; RFA, radiofrequency ablation.
*Showed that there had missing data at the time of radiofrequency ablation in this parameter.
TABLE 3. Factors Associated With Recurrence After RFA for HCC by Univariate and Multivariate Analysis
Univariate AnalysisMultivariate Analysis
Variable
Age: >65/r65y/o
Sex: Female/male
HBsAg: positive/negative*
Anti-HCV: positive/negative*
Albumin: r3.7/>3.7g/dL*
Bilirubin: >1.6/r1.6mg/dL*
ALT: >40/r40U/L
AST: >45/r45U/L
Platelet: r105/>105/mm3
PTINR: >1.1/r1.1
AFP: >20/r20ng/mL
Multiple tumor (yes/no)
Tumor size: >2cm/r2cm
Creatinine: >1.5/r1.5mg/dL
Antiviral therapy (no/yes)*
Case No.
Hazard Ratio
(95% confidence interval)P
Hazard Ratio
(95% confidence interval)P
158/100
96/162
108/144
121/133
92/146
26/229
161/97
149/109
101/157
59/199
126/132
46/212
149/109
21/237
215/38
1.536 (1.703-2.128)
1.231 (0.898-1.687)
1.115 (0.973-1.277)
1.040 (0.908-1.189)
1.326 (0.951-1.848)
1.383 (0.836-2.290)
1.148 (0.834-1.582)
1.072 (0.786-1.464)
1.434 (1.047-1.964)
1.318 (0.918-1.892)
1.457 (1.070-1.984)
1.852 (1.281-2.679)
1.793 (1.303-2.468)
1.424 (0.836-2.426)
1.344 (0.856-2.108)
0.009
0.197
0.120
0.574
0.096
0.207
0.397
0.660
0.025
0.134
0.017
0.001
<0.001
0.194
0.199
1.494 (1.071-2.084)0.018
1.501 (1.076-2.094) 0.017
1.490 (1.078-2.060)
1.634 (1.127-2.369)
1.878 (1.349-2.613)
0.016
0.010
<0.001
AFP indicates a-fetoprotein; ALT, alanine aminotransferase; AST, aspartate aminotransferase; BCLC, Barcelona-Clinic Liver Cancer; HBsAg, hepatitis B
surface antigen; HCC, hepatocellular carcinoma; HCV, hepatitis C virus; PTINR, prothrombin time international normalized ratio; RFA, radiofrequency
ablation.
*Showed that there had missing data at the time of radiofrequency ablation in this parameter.
J Clin Gastroenterol?Volume 46, Number 1, January 2012Age and RFA Prognosis
r2012 Lippincott Williams & Wilkins www.jcge.com|65

Page 5

by age, total cumulative recurrence rates at 1, 2, 3, and 5
years were 26.6%, 44.6%, 60.2%, and 76.2% in younger
HCC patients and 38.7%, 59.6%, 78.1%, and 86.6% in
elder patients, respectively (P=0.009, Fig. 1B). Younger
HCC patients had significant lower incidences of develop-
ing recurrence after RFA. However, the rates of local
recurrence and intrahepatic distant recurrence were similar
between younger and elder patients (Table 1).
Multivariate analysis showed that age >65 years (HR,
1.494; 95% CI, 1.071-2.084; P=0.018), platelet count
r105/mm3(HR, 1.501; 95% CI, 1.076-2.094; P=0.017),
multinodularity (HR,1.634;
P=0.010), elevated AFP (>20ng/mL) (HR, 1.490; 95%
CI, 1.078-2.060; P=0.016), and tumor size >2cm (HR,
1.878; 95% CI, 1.349-2.613; P<0.001) were independent
risk factors associated with recurrence after RFA (Table 3).
95%CI,1.127-2.369;
Comparison of Prognosis Between Younger and
Elder HCC Patients With Tumor Size and Viral
Factors
In this cohort, younger HCC patients had smaller
tumor size and higher rates of positive HBsAg in sera than
the elder patients. In addition to multivariate analysis, we
also performed subgroup analysis to minimize the impact of
these confounding factors on the analysis of prognosis.
There were 109 patients with HCC 2cm or less in size.
Stratified by age, the overall cumulative survival rates at 1, 2,
3, and 5 years were 100.0%, 88.4%, 88.4%, and 88.4% in
younger HCC patients and 94.5%, 83.7%, 77.7%, and 64.7%
in elder patients, respectively (P=0.029; Fig. 2A). It
demonstrated that younger HCC patients had significantly
better overall survival than the elder ones in the setting of
small tumor size. Besides, there were 149 patients with HCC
>2cm in size. The overall cumulative survival rates at 1, 2, 3,
and 5 years were 97.6%, 94.9%, 85.6%, and 72.4% in
younger HCC patients and 94.7%, 82.8%, 71.7%, and 65.4%
in elder patients, respectively (P=0.159; Fig. 2B).
Regarding viral status, there were 108 patients with
positive HBsAg in sera. (Table 1) Stratified by age, the
overall cumulative survival rates at 1, 2, 3, and 5 years were
97.9%, 92.9%, 88.0%, and 83.1% in younger HCC patients
and 92.5%, 85.8%, 73.2%, and 69.3% in elder patients,
respectively (P=0.060; Fig. 2C). Besides, there were 121
patients with chronic hepatitis C. The overall cumulative
survival rates at 1, 2, 3, and 5 years were 97.3%, 92.4%,
82.7%, and 76.3% in younger HCC patients and 94.2%,
FIGURE 2. A, Cumulative overall survival in hepatocellular carcinoma (HCC) patients with tumor size r2cm stratified by age. Young
patients had significantly higher overall survival rate than elder patients (P=0.029). B, Cumulative overall survival in HCC patients with
tumor size >2cm stratified by age. The survival rate were comparable between young and elder patients (P=0.159). C, Cumulative
overall survival in HBV-related HCC patients stratified by age. Young patients had a trend of better overall survival than elder patients
(P=0.060). D, Cumulative overall survival in HCV-related HCC patients stratified by age. Young patients had a trend of higher overall
survival rate after RFA than the elder patients (P=0.076).
Kao et al J Clin Gastroenterol?Volume 46, Number 1, January 2012
66|www.jcge.com
r2012 Lippincott Williams & Wilkins

Page 6

74.7%, 68.7%, and 63.4% in elder patients, respectively.
(P=0.076; Fig. 2D). Consequently, younger HCC patients
had a trend of higher overall survival rate after RFA than
elder patients both in patients with chronic hepatitis
B and C.
Comparison of Prognosis Between Younger and
Elder Patients With BCLC Stage 0 HCC
In this cohort, 92 patients with solitary HCC <2cm in
size were defined as very early small HCC and the
Barcelona-Clinic Liver Cancer (BCLC) stage 0. The overall
cumulative survival rates at 1, 2, 3, and 5 years were 96.5%,
92.6%, 83.7%, and 77.3%, respectively. Stratified by age,
the overall cumulative survival rates were 100.0%, 96.4%,
89.3%, and 89.3% in younger HCC patients and 93.3%,
85.3%, 78.3%, and 63.6% in elder patients, respectively
(P=0.027; Fig. 3A). The overall survival rates were
significantly higher in younger patients with BCLC stage
0 HCC. Only age >65 years (HR, 4.170; P=0.034) and
serum albumin levels r3.7g/dL (HR, 7.811; P=0.002)
were independent risk factors associated with poor overall
survival by multivariate analysis (Table 4).
Regarding recurrence, 46 patients with BCLC stage 0
HCC developed recurrence after RFA with median time of
20.3±14.5 months. The cumulative rate of recurrence at 1, 2,
3, and 5 years were 20.1%, 34.5%, 56.5%, and 68.4%,
respectively. Elder and younger patients had comparable
rates of developing recurrence after RFA (P=0.609;
Fig. 3B). By multivariate analysis, only higher serum bilirubin
level (>1.6mg/dL) was associated with recurrence for
patients with BCLC stage 0 HCC undergoing RFA (Table 4).
DISCUSSION
This study compares the clinicopathologic character-
istics and long-term outcomes after RFA between younger
and elderly HCC patients. Younger patients have a trend of
better liver functional reserve, presenting with higher serum
albumin levels (P=0.074), than elder patients. Outcomes
are also much better in younger patients, with cumulative
overall survival rates at 5 years of 81.3% (65.4% in elder
patients, P=0.008). Among patients with BCLC stage 0
HCC, the cumulative overall survival rate of younger
patients is as high as 89.3% compared with 69.3% in the
elderly patients (P=0.027).
Consistent with previous reports, this study demon-
strates that liver functional reserve substantially influences
overall survival and recurrence rates for patients with small
HCC who underwent RFA.10,11,16,25Prothrombin time,
serum albumin and bilirubin levels, and platelet count are
strong predictors of outcome, whereas tumor factors like
serum AFP level, tumor size, and multinodularity are major
predictors of recurrence. Nevertheless, although larger
tumor size (>2cm) and multinodularity are associated
with recurrence after RFA, they are not correlated with
overall survival. As multinodularity may indicate intrahe-
patic metastasis or multicentric origins of HCC, and tumor
size is a key risk factor of vascular invasion, which is an
important factor in turmor recurrence,26,27it is reasonable
to hypothesize that these 2 factors are closely correlated
with recurrence after RFA. However, majority of patients
who developed tumor recurrence after RFA in this study
cohort have been detected by close surveillance. The sizes of
the recurrent tumors are relatively small so they can be
ablated completely by another course of RFA therapy.
Consequently, long-term outcomes for patients with tumor
recurrence after RFA are relatively good. It implies that
liver functional reserve may play a more important role in
determining the overall survival of small HCC after RFA,
in which the effects of tumor factors are minimized.19Of
note, for patients with tumor size of 2cm or less or in
BCLC stage 0, younger patients had significantly higher
overall survival rate than the elder one due to their better
liver functional reserve.
In this cohort, younger patients have higher rates of
chronic HBV infection compared with elder patients (53.6%
vs. 38.9%, P=0.009). Most HBV carriers in Taiwan have
been infected with the virus during the perinatal period or in
early childhood, whereas HCV exposure usually occurs in
adulthood. Moreover, as HCV is an RNA virus that cannot
be integrated into the host genome, HCV-mediated hepato-
carcinogenesis is mainly caused by long-lasting chronic
inflammation, liver regeneration, and fibrosis. In contrast,
HBV DNA can integrate into the host genome and may
directly induce HCC without liver cirrhosis.28Consequently,
it can be expected that hepatitis C-related HCC patients are
elder than hepatitis B-related HCC patients. Nevertheless,
FIGURE 3. A, Cumulative overall survival in hepatocellular
carcinoma (HCC) patients with Barcelona-Clinic Liver Cancer
(BCLC) stage 0 stratified by age. Young patients had better
overall survival rate than elder patients (P=0.027). B, Cumulative
recurrence in HCC patients with BCLC stage 0 stratified by age.
The incidence of recurrence were comparable between young
and elder patients (P=0.609).
J Clin Gastroenterol?Volume 46, Number 1, January 2012Age and RFA Prognosis
r2012 Lippincott Williams & Wilkins www.jcge.com|67

Page 7

viral factor is not a significant risk factor in determining both
the overall survival and recurrence for HCC patients after
RFA in our study. These results consist with our previous
study, in which viral factors are not apparent in determining
outcomes of HCC patients who underwent resection
surgery.29In this study, younger HCC patients had a trend
of higher overall survival rate after RFA than elder patients
both in patients with chronic hepatitis B and C. The relative
small patient number in each subgroup is the possible cause
to make age factor fail to reach statistically significant in
determining post-RFA prognosis in the stratified analysis.
More large-scale studies are needed to elucidate the impact of
age on the post-RFA prognosis for HCC patients from
different viral status.
The male-to-female ratio is higher in younger HCC
patients. It may be related to differences of the dominant
hepatitis virus in the population. Recent studies reveal a
close interplay among androgens, androgen receptor
activities, and HBV hepatocarcinogenesis.30,31Androgens
can promote the activation of HBV transcription and
replication by direct binding to androgen-responsive
element sites in viral enhancer I.30In contrast, the HBx
oncoprotein can also interact with the androgen receptor-
signaling pathway to enhance hepatocarcinogenesis by
modulating cell proliferation and survival.31The positive
regulatory loop between HBx and androgen receptor may
lead to increased HBV viral titers and elevated risk of HCC
in male HBV carriers. As more patients in the younger
HCC group are chronic carriers of HBV, this mechanism
may explain the higher male-to-female ratio in this group.
Antiviral therapy can preserve liver function and
reduce the risk of developing cirrhosis and HCC in patients
with chronic HBV or HCV infection.32,33
whether or not it can decrease HCC recurrences after
curative treatment remains controversial.34–36In this study,
patients receiving antiviral therapy after RFA have better
overall survival than those without therapy, although this
has no effect on recurrence. As antiviral therapy can restore
liver functional reserve, which is crucial for determining
overall survival in patients with small HCC undergoing
RFA, the use of antiviral therapy after RFA can improve
clinical outcomes. In this cohort, a higher proportion of
younger HCC patients received antiviral therapy after
RFA. The mechanism of better prognosis for younger HCC
patients who underwent RFA may be due to their better
liver functional reserve and higher rates of receiving
antiviral therapy to ameliorate liver inflammation, reduce
fibrosis, and improve liver functional reserve.
Our recent study demonstrates that tumor factors
dominate the emergence of early recurrence (recurrence
However,
TABLE 4. Univariate and Multivariate Analysis of the Prognostic Factors for Overall Survival and Recurrence for Patients With BCLC 0
HCC After RFA
Univariate Analysis Multivariate Analysis
VariableCase No.
Hazard Ratio (95%
confidence interval)P
Hazard Ratio (95%
confidence interval)P
Survival
Age: >65/r65y/o
Sex: Female/Male
HBsAg: positive/negative*
Anti-HCV: positive/negative
Albumin: r3.7/>3.7g/dL*
Bilirubin: >1.6/r1.6mg/dL*
ALT: >40/r40U/L
AST: >45/r45U/L
Platelet: r105/>105/mm3
PTINR: >1.1/r1.1
AFP: >20/r20ng/mL
Tumor size: >1.5cm/r1.5cm
Creatinine: >1.5/r1.5mg/dL
Antiviral therapy (No/Yes)*
Recurrence
Age >65/r65y/o
Sex Female/Male
HBsAg positive/negative*
Anti-HCV positive/negative
Albumin r3.7/>3.7g/dL*
Bilirubin >1.6/r1.6mg/dL*
ALT >40/r40U/L
AST >45/r45U/L
Platelet r105/>105/mm3
PTINR >1.1/r1.1
AFP >20/r20ng/mL
Tumor size >1.5cm/r1.5cm
Creatinine >1.5/r1.5mg/dL
Antiviral therapy (No/Yes)*
47/45
35/57
40/51
47/45
30/55
6/85
64/28
59/33
38/54
21/71
48/44
43/49
6/86
68/21
3.873 (1.063-14.110)
2.008 (0.675-5.978)
1.138 (0.585-2.208)
1.279 (0.429-3.817)
6.862 (1.854-25.397)
2.375 (0.525-10.738)
2.734 (0.606-12.346)
1.491 (0.459-4.850)
2.204 (0.738-6.583)
1.403 (0.431-4.567)
1.159 (0.389-3.454)
3.792 (1.042-13.795)
1.303 (0.169-10.034)
4.043 (0.525-31.159)
0.027
0.210
0.704
0.658
0.004
0.261
0.191
0.507
0.157
0.574
0.791
0.043
0.799
0.180
4.170 (1.111-15.644) 0.034
7.811 (2.091-29.176)0.002
47/45
35/57
40/51
47/45
30/55
6/85
64/28
59/33
38/54
21/71
48/44
43/49
6/86
68/21
1.164 (0.649-2.088)
1.174 (0.646-2.132)
1.435 (0.889-2.315)
1.050 (0.588-1.880)
2.178 (1.161-4.083)
3.660 (1.524-8.788)
1.366 (0.707-2.641)
1.037 (0.569-1.890)
1.156 (0.638-2.095)
1.708 (0.894-3.261)
1.283 (0.717-2.297)
1.429 (0.799-2.554)
1.244 (0.385-4.024)
1.219 (0.603-2.464)
0.609
0.598
0.139
0.867
0.015
0.004
0.353
0.907
0.632
0.105
0.402
0.229
0.715
0.581
3.925 (1.623-9.494)0.002
AFP indicates a-fetoprotein; ALT, alanine aminotransferase; AST, aspartate aminotransferase; BCLC, Barcelona-Clinic Liver Cancer; HBsAg, hepatitis B
surface antigen; HCC, hepatocellular carcinoma; HCV, hepatitis C virus; PTINR, prothrombin time international normalized ratio; RFA, radiofrequency
ablation.
*Showed that there had missing data at the time of radiofrequency ablation in this parameter.
Kao et al J Clin Gastroenterol?Volume 46, Number 1, January 2012
68|www.jcge.com
r2012 Lippincott Williams & Wilkins

Page 8

occurring within 2 years of therapy), whereas field factors,
such as inflammation and liver functional reserve, are
crucial in the development of late recurrence.26,27The
impact of antiviral therapy on reducing HCC recurrence
after RFA may need longer therapy durations. Hence, more
prospective studies with larger patient numbers and longer
treatment durations are warranted to investigate the true
effect of antiviral therapy on tumor recurrence after RFA.
Some limitations to this analysis were noted. In Table 2,
there were only 45 events (deaths) in our study which exami-
ned 8 variables in the multivariable analysis. The sufficient
numbers of events required for a strong multivariate analysis
are still debated. In the report by Cox,37the number of events
needed was not specified. However, some investigators have
recommended at least 10 events per predictor should be used
for an accurately interpreted multivariate analysis.38Despite
the potential limitation of a relatively small number of
patients reaching the events (n=45), the multivariate analy-
sis showed age to be a significant independent prognostic
factors of both overall survival and recurrence after RFA for
HCC. Further large-scale studies are warranted to confirm
age in predicting the prognosis of HCC after RFA. Besides,
age per se may be a major confounder to influence the overall
survival and recurrence for HCC patients undergoing RFA.
The mechanism and crucial risk factors attributing to
poor prognosis may need more prospective studies to be
elucidated.
In conclusion, this study demonstrates that both liver
functional reserve (serum albumin level, PTINR, platelet
count, and antiviral therapy) and tumor factors (tumor size,
number, and AFP level) were crucial in determining post-
RFA prognosis in HCC patients. Moreover, younger HCC
patients have better overall survival and lower incidence of
developing recurrence after RFA than elder patients,
especially for those with tumor size 2cm or less or in
BCLC stage 0.
REFERENCES
1. Omata M, Lesmana LA, Tateishi R, et al. Asian Pacific
Association for the Study of the Liver consensus recommenda-
tions on hepatocellular carcinoma. Hepatol Int. 2010;4:439–474.
2. Ferenci P, Fried M, Labrecque D, et al. Hepatocellular
carcinoma (HCC): a global perspective. J Clin Gastroenterol.
2010;44:239–245.
3. Huo TI, Hsia CY, Huang YH, et al. Selecting a short-term
prognostic model for hepatocellular carcinoma: comparison
between the model for end-stage liver disease (MELD),
MELD-sodium, and five cancer staging systems. J Clin
Gastroenterol. 2009;43:773–781.
4. Hong SN, Lee SY, Choi MS, et al. Comparing the outcomes of
radiofrequency ablation and surgery in patients with a single
small hepatocellular carcinoma and well-preserved hepatic
function. J Clin Gastroenterol. 2005;39:247–252.
5. Bruix J, Sherman M. Management of hepatocellular carcino-
ma: an update. Hepatology. 2011;53:1020–1022.
6. Huo TI, Huang YH, Su CW, et al. Validation of the HCC-
MELD for dropout probability in patients with small
hepatocellular carcinoma undergoing locoregional therapy.
Clin Transplant. 2008;22:469–475.
7. Germani G, Pleguezuelo M, Gurusamy K, et al. Clinical
outcomes of radiofrequency ablation, percutaneous alcohol
and acetic acid injection for hepatocelullar carcinoma: a meta-
analysis. J Hepatol. 2010;52:380–388.
8. Lencioni R. Loco-regional treatment of hepatocellular carci-
noma. Hepatology. 2010;52:762–773.
9. Lin SM, Lin CJ, Lin CC, et al. Randomised controlled trial
comparing percutaneous radiofrequency thermal ablation,
percutaneous ethanol injection, and percutaneous acetic acid
injection to treat hepatocellular carcinoma of 3cm or less. Gut.
2005;54:1151–1156.
10. N’Kontchou G, Mahamoudi A, Aout M, et al. Radio-
frequency ablation of hepatocellular carcinoma: long-term
results and prognostic factors in 235 Western patients with
cirrhosis. Hepatology. 2009;50:1475–1483.
11. Tateishi R, Shiina S, Teratani T, et al. Percutaneous radio-
frequency ablation for hepatocellular carcinoma: an analysis of
1000 cases. Cancer. 2005;103:1201–1209.
12. Camma C, Di Marco V, Orlando A, et al. Treatment of
hepatocellular carcinoma in compensated cirrhosis with radio-
frequency thermal ablation (RFTA): a prospective study.
J Hepatol. 2005;42:535–540.
13. Livraghi T, Meloni F, Di Stasi M, et al. Sustained complete
response and complications rates after radiofrequency ablation
of very early hepatocellular carcinoma in cirrhosis: is resection
still the treatment of choice? Hepatology. 2008;47:82–89.
14. Santambrogio R, Opocher E, Zuin M, et al. Surgical resection
versus laparoscopic radiofrequency ablation in patients with
hepatocellular carcinoma and Child-Pugh class a liver cirrho-
sis. Ann Surg Oncol. 2009;16:3289–3298.
15. Hung HH, Chiou YY, Hsia CY, et al. Survival rates are
comparable after radiofrequency ablation or surgery in
patients with small hepatocellular carcinomas. Clin Gastro-
enterol Hepatol. 2011;9:79–86.
16. Waki K, Aikata H, Katamura Y, et al. Percutaneous radio-
frequency ablation as first-line treatment for small hepatocel-
lular carcinoma: results and prognostic factors on long-term
follow up. J Gastroenterol Hepatol. 2010;25:597–604.
17. Mirici-Cappa F, Gramenzi A, Santi V, et al. Treatments for
hepatocellular carcinoma in elderly patients are as effective as
in younger patients: a 20-year multicentre experience. Gut.
2010;59:387–396.
18. Hiraoka A, Michitaka K, Horiike N, et al. Radiofrequency
ablation therapy for hepatocellular carcinoma in elderly
patients. J Gastroenterol Hepatol. 2010;25:403–407.
19. Hung HH, Su CW, Lai CR, et al. Fibrosis and AST to platelet
ratio index predict post-operative prognosis for solitary small
hepatitis B-related hepatocellular carcinoma. Hepatol Int.
2010;4:691–699.
20. Tong MJ, Chavalitdhamrong D, Lu DS, et al. Survival in
Asian Americans after treatments for hepatocellular carcino-
ma: a seven-year experience at UCLA. J Clin Gastroenterol.
2010;44:e63–70.
21. Kikuchi LO, Paranagua-Vezozzo DC, Chagas AL, et al.
Nodules less than 20mm and vascular invasion are predictors
of survival in small hepatocellular carcinoma. J Clin Gastro-
enterol. 2009;43:191–195.
22. Kim JH, Choi MS, Lee H, et al. Clinical features and
prognosis of hepatocellular carcinoma in young patients from
a hepatitis B-endemic area. J Gastroenterol Hepatol. 2006;21:
588–594.
23. Chen CH, Chang TT, Cheng KS, et al. Do young hepatocel-
lular carcinoma patients have worse prognosis? The paradox of
age as a prognostic factor in the survival of hepatocellular
carcinoma patients. Liver Int. 2006;26:766–773.
24. Bruix J, Sherman M, Llovet JM, et al. Clinical management of
hepatocellular carcinoma: conclusions of the Barcelona-2000
EASL Conference. J Hepatol. 2001;35:421–430.
25. Lam VW, Ng KK, Chok KS, et al. Risk factors and prognostic
factors of local recurrence after radiofrequency ablation of
hepatocellular carcinoma. J Am Coll Surg. 2008;207:20–29.
26. Wu JC, Huang YH, Chau GY, et al. Risk factors for early and
late recurrence in hepatitis B-related hepatocellular carcinoma.
J Hepatol. 2009;51:890–897.
27. Nathan H, Schulick RD, Choti MA, et al. Predictors of
survival after resection of early hepatocellular carcinoma. Ann
Surg. 2009;249:799–805.
28. Tan A, Yeh SH, Liu CJ, et al. Viral hepatocarcinogenesis: from
infection to cancer. Liver Int. 2008;28:175–188.
J Clin Gastroenterol?Volume 46, Number 1, January 2012 Age and RFA Prognosis
r2012 Lippincott Williams & Wilkinswww.jcge.com|69

Page 9

29. Kao WY, Su CW, Chau GY, et al. A comparison of prognosis
between patients with hepatitis B and C virus-related
hepatocellular carcinoma undergoing resection surgery. World
J Surg. 2011;35:858–867.
30. Wang SH, Yeh SH, Lin WH, et al. Identification of androgen
response elements in the enhancer I of hepatitis B virus: a
mechanism for sex disparity in chronic hepatitis B. Hepatology.
2009;50:1392–1402.
31. Chiu CM, Yeh SH, Chen PJ, et al. Hepatitis B virus X protein
enhances androgen receptor-responsive gene expression de-
pending on androgen level. Proc Nat Acda Sci U S A.
2007;104:2571–2578.
32. Aronsohn A, Reau N. Long-term outcomes after treatment
with interferon and ribavirin in HCV Patients. J Clin
Gastroenterol. 2009;43:661–671.
33. Sung JJY, Tsoi KKF, Wong VWS, et al. Meta-analysis:
treatment of hepatitis B infection reduces risk of hepatocellular
carcinoma. Aliment Pharmacol Ther. 2008;28:1067–1077.
34. Mazzaferro V, Romito R, Schiavo M, et al. Prevention of
hepatocellular carcinomarecurrence
after liver resection in HCV cirrhosis. Hepatology. 2006;44:
1543–1554.
35. Li N, Lai EC, Shi J, et al. A comparative study of antiviral
therapy after resection of hepatocellular carcinoma in the
immune-active phase of hepatitis B virus infection. Ann Surg
Oncol. 2010;17:179–185.
36. Breitenstein S, Dimitroulis D, Petrowsky H, et al. Systematic
review and meta-analysis of interferon after curative treatment
of hepatocellular carcinoma in patients with viral hepatitis. Br
J Surg. 2009;96:975–981.
37. Cox DR. Regression models and life tables. J R Statist Soc B.
1972;34:187–220.
38. Bradburn MJ, Clark TG, Love SB, et al. Survival analysis part
III: multivariate data analysis: choosing a model and assessing
its adequacy and fit. Br J Cancer. 2003;89:605–611.
withalpha-interferon
Kao et alJ Clin Gastroenterol?Volume 46, Number 1, January 2012
70|www.jcge.com
r2012 Lippincott Williams & Wilkins