American Thyroid Association Design and Feasibility
of a Prospective Randomized Controlled Trial
of Prophylactic Central Lymph Node Dissection
for Papillary Thyroid Carcinoma
Tobias Carling,1Sally E. Carty,2Maria M. Ciarleglio,3David S. Cooper,4Gerard M. Doherty,5
Lawrence T. Kim,6Richard T. Kloos,7Ernest L. Mazzaferri Sr.,8Peter N. Peduzzi,3
Sanziana A. Roman,1Rebecca S. Sippel,9Julie A. Sosa,1Brendan C. Stack Jr.,10
David L. Steward,1 1Ralph P. Tufano,12R. Michael Tuttle,13and Robert Udelsman,1
for the American Thyroid Association Surgical Affairs Committee
Background: The role of prophylactic central lymph node dissection in papillary thyroid cancer (PTC) is con-
troversial in patients who have no pre- or intraoperative evidence of nodal metastasis (clinically N0; cN0). The
controversy relates to its unproven role in reducing recurrence rates while possibly increasing morbidity (per-
manent hypoparathyroidism and unintentional recurrent laryngeal nerve injury).
Methods and Results: We examined the design and feasibility of a multi-institutional prospective randomized
controlled trial of prophylactic central lymph node dissection in cN0 PTC. Assuming a 7-year study with 4 years
of enrollment, 5 years of average follow-up, a recurrence rate of 10% after 7 years, a 25% relative reduction in the
rate of the primary endpoint (newly identified structural disease; i.e., persistent, recurrent, or distant metastatic
disease) with central lymph node dissection and an annual dropout rate of 3%, a total of 5840 patients would
have to be included in the study to achieve at least 80% statistical power. Similarly, given the low rates of
morbidity, several thousands of patients would need to be included to identify a significant difference in rates of
permanent hypoparathyroidism and unintentional recurrent laryngeal nerve injury.
Conclusion: Given the low rates of both newly identified structural disease and morbidity after surgery for cN0
PTC, prohibitively large sample sizes would be required for sufficient statistical power to demonstrate signifi-
cant differences in outcomes. Thus, a prospective randomized controlled trial of prophylactic central lymph node
dissection in cN0 PTC is not readily feasible.
cases of thyroid cancer were diagnosed in 2010 with a total of
hyroid cancer is the most common endocrine malig-
nancy. In the United States, an estimated 44,670 new
1690 deaths due to the disease (1). The discrepancy between
thyroid (95.2%) and the total proportion of endocrine cancer
deaths (65.8%) reflects the long-term survival associated with
thyroid malignancies, given its relatively indolent nature (1).
Authors are listed in alphabetical order.
1Department of Surgery, School of Medicine;3Yale Center for Analytical Sciences, School of Public Health; Yale University, New Haven,
2Department of Surgery, Division of Endocrine Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
4Division of Endocrinology and Metabolism, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
5Department of Surgery, University of Michigan Health Systems, Ann Arbor, Michigan.
Departments of6Surgery and10Otolaryngology—Head and NeckSurgery, University of Arkansas for Medical Sciences, Little Rock, Arkansas.
7Divisions of Endocrinology, Diabetes and Metabolism, and Nuclear Medicine; Departments of Internal Medicine and Radiology; The
Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, and The Ohio State University Comprehensive Cancer Center, The
Ohio State University, Columbus, Ohio.
8Divisions of Endocrinology, Diabetes and Metabolism, Department of Internal Medicine, University of Florida, Gainesville, Florida.
9Department of Surgery, University of Wisconsin, Madison, Wisconsin.
11Department of Otolaryngology—Head and Neck Surgery, College of Medicine, University of Cincinnati, Cincinnati, Ohio.
12Department of Otolaryngology—Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
13Department of Endocrinology, Memorial Sloan-Kettering Cancer Center, New York, New York.
Volume 22, Number 3, 2012
ª Mary Ann Liebert, Inc.
The vast majority (85%–95%) of these patients have papillary
thyroid cancer (PTC).
Surgery, radioactive iodine treatment, and thyroid hor-
mone suppression are the mainstays of treatment for PTC (2).
Due to the overall excellent outcomes in patients with PTC
and the lack of prospective controlled trials, many of the
current recommendations and guidelines for treatment of
radioactive iodine treatment in low-risk patients, and the ex-
tent and frequency of surveillance. With regard to the extent
of surgery for PTC, the debate has shifted from thyroid lo-
bectomy versus total thyroidectomy (3), to a debate regarding
the initial management of cervical lymph nodes (4).
Lymph nodes typically involved in PTC are level VI (cen-
tral compartment); levels II, III, and IV lymph nodes along the
internal jugular vein corresponding to the upper, mid, and
lower neck; and less frequently the level V (posterior triangle
of the neck) lymph nodes. There is general agreement that
formal lymph node dissection should be performed in the
setting of imageable, biopsy-proven, or palpable nodal dis-
ease. The American Thyroid Association (ATA) Guidelines
compartment (level VI) neck dissection should be considered
for patients with papillary thyroid carcinoma and suspec-
ted Hu ¨rthle cell carcinoma’’ (5). These recommendations
caused significant controversy because of the ambiguity
leading to vastly different interpretations amongst clinicians
and the paucity of strong supporting data. Thus, the revised
2009 management guidelines state ‘‘Prophylactic central-
compartment neck dissection (ipsilateral or bilateral) may be
performed in patients with papillary thyroid carcinoma with
clinically uninvolved central neck lymph nodes, especially for
advanced primary tumors (T3 or T4; Grade C recommenda-
tion; expert opinion)’’ (2). The current guidelines also indicate
that ‘‘these recommendations should be interpreted in the
light of available surgical expertise,’’ acknowledging that this
approach could be associated with increased morbidity es-
Although central lymph node dissection can be achieved
with low morbidity in experienced hands, prophylactic dis-
regional lymph node disease in PTC may have been under-
stated in the past partly due to the excellent overall prognosis
associated with well-differentiated thyroid cancer and the
observation that lymph node metastases did not influence
survival rates (7). More recent large-scale population-based
studies, mainly from Sweden, have shown that regional
lymph node metastases among patients with thyroid cancer
impact both local recurrence and cause-specific mortality
(8,9). The association between lymph node metastasis and
mortality seems to be preferentially identified in older pa-
tients (10,11), whereas such an association is less certain in
their younger counterparts. Further complicating these ana-
lyses are potential prognostic differences including BRAF
mutation status, and between microscopic (more likely to be
clinically N0; cN0) and macroscopic lymph node metastases
(less likely to be cN0), which are often not independently
evaluated in retrospective cohort analyses. These competing
considerations coupled with the drive to achieve low or
undetectable thyroglobulin (Tg) levels in surveillance have
refocused the debate on how best to manage regional nodal
spread. The goals of treatment are no longer aimed at simply
avoiding mortality. The secondary goals of achieving athyr-
follow-up have become the primary endpoints of therapy for
many patients and treating physicians (12).
While possibly beneficial, prophylactic central lymph node
rate of complications, including permanent hypoparathy-
roidism and recurrent laryngeal nerve injury (4,6). In an at-
tempt to better define the risk–benefit ratio of prophylactic
central lymph node dissection, several groups have consid-
ered embarking on prospective clinical trials to address this
The inherent weakness of retrospective analyses limits the
in order to provide the basis for a prospective randomized
controlled trial comparing prophylactic central node dissec-
tion versus no prophylactic central node dissection for cN0
PTC, the feasibility of such a study was analyzed by a mul-
tidisciplinary subcommittee of the ATA Surgical Affairs
Committee. The data are extrapolated from current retro-
spective and meta-analysis studies and examined in terms of
their implications on trial design and sample size.
The study would be a multi-institutional, prospective,
randomized, blinded (until total thyroidectomy has been
performed) study (Table 1). All adult patients (‡18 years of
age) with fine-needle aspiration (FNA) proven PTC and cN0
would be eligible for inclusion in the study. Informed consent
would be obtained for all participants, and approval from the
institutional review boards would be sought from partici-
As part of the initial assessment, demographic information
(age, sex, history of radiation exposure, history of thyroid
disease, past and current use of thyroid hormone treatment,
known or suspected familial PTC) and the baseline charac-
teristics outlined in Table 2 would be obtained.
All patients would need to have documentation of
normal vocal cord mobility by preoperative laryngoscopy. A
Table 1. Summary of Clinical Trial Key Points
? Multi-institutional prospective randomized controlled trial
? Patients (‡18 years of age) with FNA proven PTC are
candidates for enrollment.
? Patients with pre- and intra-operative stage T (1–4), cN0,
cM0 are randomized in the operating room after total
thyroidectomy has been performed.
? Randomization to group A (central neck dissection) or
group B (no central neck dissection).
? The primary endpoint is newly identified structural
disease, which may include persistent, recurrent, or distant
? Postoperative RAI ablation therapy is standardized to
50mCi in all patients.
? Surveillance and TSH suppression is performed in accor-
dance with ATA guidelines.
ATA, American Thyroid Association; FNA, fine-needle aspiration;
PTC, papillary thyroid carcinoma; RAI, radioactive iodine; TSH,
238CARLING ET AL.
preoperative comprehensive neck ultrasound (US) of the
thyroid and central and lateral neck compartments would be
required as part of the routine preoperative planning for di-
agnosed PTC (13). US-guided FNA would be performed of
the primary tumor and selected lymph nodes suspicious for
metastatic disease in the central and/or lateral neck as part of
the routine preoperative planning for PTC. The slides of pa-
tients with a cytological diagnosis of PTC at an outside hos-
pital/institution would be reviewed by a cytopathologist at
the participating institution. For cases in which there is dis-
agreement between the findings at the outside institution and
at the participating institution, the preoperative diagnosis
would be based on the findings at the participating institution
after review at a cytopathology consensus conference and/or
referral to a third consulting cytopathologist. The use of mo-
lecular diagnostic tools (e.g., BRAF V600E mutational status)
as an aid to the cytopathological diagnosis would not change
the eligibility to participate in the study but would be tracked
(e.g., a patient with indeterminate FNA results and BRAF
mutation positivity, which indicates a preoperative diagnosis
of PTC, would be eligible for enrollment).
Only patients with pre- and intraoperatively diagnosed T
(1–4), cN0, cM0 PTC would be randomized (Fig. 1). We esti-
mate that approximately 15% of patients with PTC would
present with metastatic disease or be found to have lateral
and/or central node metastasis during the initial evaluation
(14–20).These patientswouldbe excludedfromthestudy and
would undergo standard management. Furthermore, we es-
timate that approximately 10% of patients with PTC would
based on surgeon suspicion or intraoperative frozen section
analysis (12,14–20). Intraoperative frozen section analysis of
lymph nodes would be obtained at the discretion of the op-
erating surgeon. Patients with intraoperative positive central
lymph node metastasis would be excluded from the study
and undergo standard surgical management. Similarly, the
rare cases with lateral lymph node metastasis diagnosed in-
traoperatively would not be included. In addition, we esti-
mate thatapproximately 2%of patients with PTC would have
patients would be excluded from the study and undergo
standard surgical management, since concomitant parathy-
roidectomy likely would affect the incidence of postoperative
hypoparathyroidism. Other exclusion criteria would be pre-
vious central cervical operation and inability to give informed
consent or meet follow-up requirements.
Intraoperative randomization process
After a total thyroidectomy and central neck evaluation by
the surgeon and when no suspicious lymphadenopathy has
been detected, patients would be randomized to either pro-
phylactic central lymph node dissection or to no central
lymph node dissection using equal allocation. The individual
surgeon would be blinded to the randomization process until
after total thyroidectomy. A web-based intraoperative ran-
domization procedure would be developed, accessible to
Central neck dissection
In patients randomized to the treatment arm, an ipsilateral
prophylactic central lymph node dissection would be per-
formed for unilateral PTC. For clinically apparent bilateral
PTC, a bilateral central lymph node dissection would be
performed. The goal of a prophylactic central lymph node
dissection is to remove all lymphatic tissue en bloc. The su-
perior margin is at the level of the hyoid bone, the inferior
margin is at the level of the brachiocephalic vessels, the lateral
the contralateral margin is past the midline of the trachea but
(22). The dissection includes lymph nodes posterior (deep) to
the recurrent laryngeal nerve. The number of removed lymph
nodes would be recorded on the pathology report, thus
mandating collaboration with the pathology departments at
the participating institutions.
Table 2. Time Points of Scheduled Surveillance
Pre-opPOD 1 1–2 wk1 mo3 mo 6 mo 9 mo Annually thereafter
Chest X ray
I 131 therapy (50mCi)
I 131 WBS
Quality of Life Survey
Adverse events monitoring
aPathology report includes TNM stage, size, multifocality, margins, extrathyroidal extension number of lymph nodes removed, number of
positive lymph nodes, presence of parathyroid tissue; POD, postoperative day; TSH, thyrotropin; PTH, parathyroid hormone; Tg,
thyroglobulin; WBS, whole-body scan.
bAll measurements of Tg would include measurement of thyroglobulin antibodies.
DESIGN AND FEASIBILITY OF A PROSPECTIVE TRIAL239
Parathyroid autotransplantation of one or more normal
parathyroid glands would be performed at the discretion of
the operating surgeon after frozen section confirmation.
The primary endpoint is newly identified structural dis-
ease,1which may include persistent, recurrent, or distant
metastatic disease defined as follows.
1) Persistent disease would be defined as cervical/supe-
rior mediastinal disease identified by an imaging study
(US, radioisotope scan, computed tomography [CT],
magnetic resonance imaging [MRI, positron emission
tomography [PET], etc.), which would ideally be biopsy
proven. Direct measurements of recombinant human
thyrotropin (rhTSH)-stimulated (Thyrogen?, Genzyme,
Cambridge, MA) pre–radioactive iodine treatment Tg
levels (and antibodies) would aid in identifying per-
sistent structural disease. Persistent disease is defined
as being diagnosed£6 months after total thyroidec-
tomy and radioactive iodine treatment.
2) Recurrent/distant metastatic disease would be defined
as occurring>6 months after total thyroidectomy and
radioactive iodine treatment.
a. Locoregional recurrence is defined as cervical/su-
perior mediastinal disease identified by an imaging
study (US, radioisotope scan, CT, MRI, PET, etc.)
and ideally biopsy proven. Direct measurements of
rhTSH-stimulated or unstimulated Tg levels (and
antibodies) would aid in identifying recurrent
b. Distant metastatic disease is defined as disease
identified outside of the neck by an imaging study
(US, radioisotope scan, CT, MRI, PET, etc) or biopsy
proven. Direct measurements of rhTSH-stimulated
or unstimulated Tg levels (and antibodies) would
aid in identifying distant metastatic disease.
The secondary endpoints are
1) Disease-specific mortality
2) Surgical mortality and morbidity
a. Operative mortality (defined as within 30 days post-
operatively). General operative morbidity such as
pulmonary embolism, pneumonia, cardiac complica-
b. Specific morbidities
i. Permanent hypoparathyroidism (transient hypo-
parathyroidism would be monitored but not
considered a morbidity endpoint)
(documented paresis that recovers within 6
iii. Permanent recurrent laryngeal nerve paresis
(documented paresis that extends beyond 6
iv. Cervical neck hematoma
3) Other outcomes
a. Presence of undetectable suppressed Tg at 1-year
b. Presence of undetectable stimulated Tg at 1-year
c. Biochemical persistent disease defined based on el-
evated Tg levels is more likely to represent persistent
disease rather than residual postoperative normal
thyroid tissue. Persistent disease is defined as being
diagnosed£6 months after total thyroidectomy and
radioactive iodine treatment.1
laryngeal nerve paresis
randomized controlled trial of
prophylactic central node
dissection for papillary thyroid
Study design. Prospective
1It is anticipated that occasionally the diagnosis of newly identi-
fied structural disease and biochemical persistent or recurrent dis-
ease may be debatable in individual cases (e.g., elevated Tg without
structural disease on imaging or radioisotope scan uptake that is not
biopsy proven). Such cases would be reviewed by a multidisciplin-
ary committee of investigators to determine the diagnosis of newly
identified structural disease or biochemical persistent and recurrent
240 CARLING ET AL.
d. Biochemical recurrent disease which is defined
based on elevated Tg levels in a patient with a
previously undetectable Tg diagnosed>6 months
after total thyroidectomy and radioactive iodine
e. Requirement of cervical reoperation for thyroid
cancer after initial total thyroidectomy and radioac-
tive iodine treatment.
f. Requirement of radioactive iodine treatment for
thyroid cancer after initial total thyroidectomy and
radioactive iodine treatment.
g. Operative time
h. Duration of hospital stay
i. Number of frozen section analyses during surgery
j. Molecular marker status
k. Quality of life assessment
Radioactive iodine treatment
All patients would undergo postoperative radioactive io-
dine treatment. The dose would be standardized to approxi-
mately 50mCi for all patients in both group A and B,
independent of the underlying stage of PTC. A pretherapy
whole-body iodine scan would not be obtained since it would
not affect the decision to treat or the activity of radioactive
iodine that is administered (2). The treatment would ideally
another institution/hospital would not be in violation of the
protocol. All patients would be on a pretherapy low-iodine
diet and the treatment would be performed after rhTSH
stimulation. Posttherapy whole-body iodine scanning would
be performed in all patients in accordance with ATA guide-
Surveillance and identification of newly identified
structural disease, and biochemical persistent or
recurrence as well as TSH suppression, in accordance with
ATA guidelines (2). The diagnosis of newly identified struc-
as outlined in the endpoints section. The time points for sur-
veillance are as outlined in Table 2.
Definition of surgical complications
Permanent hypoparathyroidism would be defined as re-
quirement of therapeutic vitamin D and/or calcium replace-
ment at 6 months or a fasting albumin-corrected serum
calcium below 8.0mg/dL. In this study, unintentional recur-
rent laryngeal nerve paresis would be defined as new vocal
cord paralysis diagnosed within 6 months postoperatively in
a patient who had normal vocal cord movement preopera-
tively. Permanent recurrent laryngeal nerve injury is by def-
inition persistent beyond the 6-month postoperative period.
Routine laryngoscopy would be performed in all patients at
6 months following thyroid surgery unless demonstrated to
be normal prior to 6 months postoperatively. In addition,
durations of surgery and hospital stay would be recorded.
Postoperative cervical hematoma is defined as postsurgical
bleeding requiring reoperative intervention.
Sample size estimation
Sample size was estimated for the primary outcome, newly
identified structural disease (i.e., persistent, recurrent or dis-
tant metastatic disease), using the method of Lakatos (23,24)
to approximate a discrete time hazard model. In the calcula-
tions we assumed a 7-year study with 4 years of recruitment
and 5 years of average follow-up (minimum=3 years, maxi-
mum=7 years), a type I error of 5% (two-sided), 80% power,
and a range of reductions in the hazard rate with prophylactic
central lymph node dissection compared with no central
lymph node dissection (20%, 25%, 33%, and 40%). The esti-
mates of the newly identified structural disease rate for the no
prophylactic central lymph node dissection group were ob-
tained from contemporary series and author experiences and
were assumed to not be constant over the study period. The
sample sizes were not inflated for interim monitoring for ef-
ficacy and futility, which would be approximately 4%–6%.
Sample sizes to detect differences in complication rates
between the two treatment groups were estimated for bino-
mial proportions assuming a Type I error of 5% (two-sided)
using PASS 2008 (NCSS, Kaysville, UT).
Calculations of study sample size scenarios are presented
in Table 3. For instance, assuming a 7-year study (4 years
enrollment, 3 years minimum follow-up, 7 years maximum
follow-up, 5 years average follow-up) with a newly identified
structural disease cumulative event rate of 35% after 7 years
and an annual dropout rate of 3%, a total of 1568 patients (355
primary outcome events) would be required to detect a 25%
disease with central lymph node dissection with 80% power
(Scenario 1, Table 3) at a type I error of 5% (two-sided).
However, given that patients would all be cN0 (by preoper-
ative US and intraoperative inspection), and thus represent
low-risk PTC, the estimated newly identified structural dis-
ease rate would likely be significantly lower. PTC without
a low newly identified structural disease rate, even in the
setting of histopathological presence of lymph node metas-
tasis, with rates ranging from 2% to 9 % (12,14–20). Thus, a
more realistic sample size scenario is presented in Table 3 as
Scenario 2. Given the same assumptions as for Scenario 1, but
with a cumulative 10% newly identified structural disease
rate after 7 years, a total of 5840 patients (377 primary out-
come events) would be required to achieve satisfactory sta-
tistical power. The key determinates of the study sample size
scenarios are the reduction in hazard rate and the newly
identifiedstructural diseasecumulative event rateasdepicted
in Fig. 2.
In addition, detecting an increased complication rate in
patients undergoing central neck dissection would require
large sample sizes as well. For example, assuming rates of
permanent hypoparathyroidism of 5% and 2.5% in those with
and without central neck dissection (6), respectively, would
require approximately 2000 patients to detect this difference
with 80% power. Similarly, to detect differences in rates of
unintentional permanent recurrent laryngeal nerve injury of
2% versus 1% with 80% power would require more than 5000
DESIGN AND FEASIBILITY OF A PROSPECTIVE TRIAL 241
total patients (6). In contrast, postoperative levels of serum
calcium and intact parathyroid hormone at postoperative day
1, prior to starting postoperative prophylaxis with calcium
carbonate and/or calcitriol, could be measured with more
modest sample sizes (25). However, the significance of de-
tecting differences in serum calcium and intact parathyroid
hormone on postoperative day 1 is of limited clinical value.
The use of routine prophylactic central lymph node dis-
section in PTC remains controversial. We have presented the
design and feasibility of a randomized controlled trial to
evaluate whether such an approach would lead to improved
or impaired outcomes of PTC patients. The single most im-
portant factor in calculating sample size scenarios required to
obtain sufficient statistical power is the event rate. It is well
documented that PTC without pre- or intraoperative central
neck nodal disease (i.e., cN0) has low recurrence rates, even in
the setting of histopathological presence of lymph node me-
tastasis, with rates ranging from 2% to 9 % (12,14–20). Since
event ratesarelowinthese PTCpatients,wedemonstratethat
thousands of patients would need to be included in the study
and followed for many years. As a point of reference, ap-
proximately 3%–7% of all U.S. patients with cN0 PTC would
need to be recruited into the study with long-term surveil-
lance to achieve sufficient statistical power (1). Similarly,
morbidity rates are low after surgery for PTC, and large
sample sizes would be necessary to detect a statistically sig-
nificant difference between the two groups. Permanent hy-
poparathyroidism occurs in approximately 1%–2% (range
0.8%–5.4%) of patients after total thyroidectomy (6). The re-
ported range of permanent hypoparathyroidism after total
thyroidectomy with prophylactic central lymph node dissec-
tion is 0%–14.3% (6). The rate of unintentional permanent
recurrent laryngeal nerve injury after total thyroidectomy
ranges between 0% and 5.5%, whereas the rate is 0%–5.7%
after total thyroidectomy with central lymph node dissection
(6). Similar to studies analyzing the rate of permanent hypo-
parathyroidism, these studies are retrospective and self-
reported and laryngoscopy was used selectively. Thus, the
true incidence of nerve injury is largely unknown.
The success of a multicenter prospective randomized con-
trolled trial of prophylactic central lymph node dissection in
cN0 PTC would depend largely on as much standardization
as possible of the diagnosis, treatment, and surveillance of the
study subjects. We realize that the proposed protocol is not
uncontroversial, for instance, the attempt to standardize the
operative management and postoperative radioactive iodine
treatment independent of the stage of PTC at final pathology.
randomized controlled trial of prophylactic central lymph
node dissection in cN0 PTC as a function of the cumulative
event rate (newly identified structural disease) and reduction
in hazard rate of 20%, 25%, 33%, and 40%. All scenarios
assume a fixed annual drop-out rate of 3%.
Total required sample size required in a prospective
Table 3. Evaluation of Sample Size Scenarios
Annual dropout rate
1% 2% 3%4%5%
Reduction in hazarda
N EventsN EventsN EventsN EventsN Events
aProphylactic central lymph node dissection compared with no prophylactic central lymph node dissection. For both scenarios, assuming a
7-year study (4 years enrollment, 3 years minimum follow-up, 7 years maximum follow-up, 5 years average follow-up); 5% Type I error (two-
sided); 80% power.
bAssuming the following newly identified structural disease (i.e., persistent, recurrent or distant metastatic disease) cumulative rates over
the study period: Year 1=10%, Year 2=20%, Year 3=25%, Year 4=27.5%, Year 5=30%, Year 6=32.5%, Year 7=35%
cAssuming the following newly identified structural disease (i.e., persistent, recurrent or distant metastatic disease) cumulative rates over
the study period: Year 1=3%, Year 2=5%, Year 3=6%, Year 4=7%, Year 5=8%, Year 6=9%, Year 7=10%.
242CARLING ET AL.
This could potentially hamper the enthusiasm for par-
ticipation of treating physicians and impede study subject
The current investigation did not specifically address the
costs of this hypothetical study. However, a large simple trial
years maximum follow-up, and 5 years average follow-up)
with enrollment of 5840 patients would be expensive. Ap-
proximately 30 centers would be required to enroll 50 subjects
per year over 4 years to achieve the target sample size. At a
minimum, one full-time study coordinator per study site
would be needed to enroll and follow 200 patients for study
outcomes for an average of 5 years at a total cost of approxi-
mately $15 million over a 7-year study period. In addition,
funding would be required for startup and closeout costs, a
national study coordinator, statistical and data coordinat-
ing center, site monitoring, investigator meetings, data and
safety monitoring board, etc. No funding would be requested
for participating patients, study surgeons, endocrinologists,
radiologists, pathologists, and nuclear medicine physician. No
funds would be requested for the medical care of the subjects
as it would adhere to recommended state-of-the-art practice.
We estimate that the total cost of the study would be
approximately $20 million or $3425 per enrolled study subject.
In summary, our analysis of a hypothetical randomized
controlled trial to evaluate the role of routine prophylactic
central lymph node dissection for cN0 PTC indicates that gi-
ven the low rates of newly identified structural disease and
morbidity, prohibitively large samples sizes would be re-
quired to detect statistically and clinically relevant differ-
ences between the groups. This means that no single
institution could perform this study alone. Therefore, a multi-
institutional collaborative trial would need to be done. This
would introduce significant variation in surgical techniques,
as well as local institutional variability in inclusion and fol-
low-up of patients. In addition, a large number of surgeons,
endocrinologists, radiologists, nuclear medicine physicians,
and pathologists would need to participate. These issues
conclude that a randomized controlled trial of prophylactic
central lymph node dissection in PTC is not readily feasible.
Studies reporting the absence of an outcome difference based
on small sample sizes may have inadequate statistical power
from which to draw such a conclusion.
Author Disclosure Statement
No competing financial interests exist.
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Address correspondence to:
Robert Udelsman, M.D., M.B.A.
Department of Surgery
Yale University School of Medicine
P.O. Box 208062
New Haven, CT 06520-8062
244 CARLING ET AL.