[show abstract][hide abstract] ABSTRACT: Typically, bevacizumab is initially infused for 90 min, then for 60 min, and subsequently for 30 min. The objective of the present study was to evaluate the safety profile of a short infusion of bevacizumab in Japanese colorectal cancer patients.
The records of 58 patients who received bevacizumab (5 mg/kg) from June 2010 to September 2010 were reviewed. Bevacizumab was administered for 30 min at the first time. If patients had no infusion reaction, the infusion time was shortened to 10 min.
None of the 58 patients who received bevacizumab experienced an infusion reaction (95% confidence interval 0-6.2). The only serious adverse event related to bevacizumab infusion was grade 3 proteinuria in 2 patients.
Short infusion of bevacizumab for 30 min the first time and 10 min is safe and feasible.
Anticancer research 02/2014; 34(2):1053-6. · 1.71 Impact Factor
[show abstract][hide abstract] ABSTRACT: Patritumab (U3-1287) is a human epidermal growth factor receptor-3 (HER3)-targeted antibody that blocks ligand-associated activation of HER3. This open-label, phase 1 and dose-finding study (ClinicalTrials.jp Identifier: JapicCTI-101262) aimed to assess the safety, pharmacokinetics, incidence of anti-patritumab antibody, recommended dose for subsequent clinical studies, preliminary efficacy, and patritumab-related biomarkers in Japanese patients with advanced solid tumors.
Patients received patritumab 9 or 18 mg/kg intravenously every 3 weeks until disease progression or intolerable toxicity occurred. Adverse events (AEs) were assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE version 4.0). Dose-limiting toxicities (DLTs) were evaluated from the initial dose to Cycle 1 Day 21. Tumor response was assessed with Response Evaluation Criteria in Solid Tumors (RECIST version 1.1).
Nine patients received patritumab 9 mg/kg (n = 3) or 18 mg/kg (n = 6). Five patients were male, all patients had Eastern Cooperative Oncology Group performance status (PS) ≤ 1, and median (range) age of 67 (50-69) years. No DLTs were reported. Patritumab-related AEs reported in ≥2 patients were ALT increase (three patients), thrombocytopenia, diarrhea, stomatitis, cheilitis, rash maculo-papular and AST increase (two each). Pharmacokinetics profile was similar to the preceding US phase 1 study. Soluble HER3 concentration in serum unexpectedly increased in all patients. These changes did not correlate with clinical response. Four patients had a best response of stable disease. All patients tested had negative for anti-patritumab antibody formation.
Patritumab was well tolerated up to 18 mg/kg without DLTs in Japanese patients with advanced solid tumors. Soluble HER3 increased in all patients.
Cancer Chemotherapy and Pharmacology 01/2014; · 2.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Combination chemotherapy with trastuzumab and cisplatin plus capecitabine or 5-fluorouracil has been used as a standard regimen for HER2-positive gastric cancer (GC) since the Trastuzumab for Gastric Cancer (ToGA) trial. Before the ToGA trial, HER2-positive GC in Japan was treated with S-1 plus cisplatin (SP). The primary objective of this retrospective study was to explore the efficacy of SP in HER2-positive GC.
We reviewed patients who had received SP as first-line chemotherapy at our institute between April 2007 and March 2011 and from whom we had enough samples to examine HER2 status. Seventy-seven patients fulfilled the selection criteria and were tested for HER2 status with immunohistochemical staining (IHC) and fluorescence in situ hybridization. The patients' backgrounds were investigated to evaluate the clinicopathologic features of their HER2-positive GC, including survival.
Seven (9.1 %) of 77 patients were judged to be IHC3+, and all of these had predominantly differentiated histology. HER2 positivity was associated with differentiated histology (P = 0.016) and liver metastasis (P = 0.025). Median overall survival was 23.6 months [95 % confidence interval (CI) 0.8-44.7] in HER2-positive GC and 12.9 months (95 % CI 8.3-17.5) in HER2-negative disease, but the difference was not statistically significant (P = 0.615). In multivariate analysis, HER2 status was not associated with survival outcomes.
Because of the retrospective nature of this study, we cannot conclude whether HER2 status influences the survival of patients who receive SP as first-line chemotherapy. Our study provides important historical data for prospective phase II studies of SP plus trastuzumab.
International Journal of Clinical Oncology 11/2013; · 1.41 Impact Factor
[show abstract][hide abstract] ABSTRACT: Studies done in Asia have shown that a regimen of S-1 plus oxaliplatin (SOX) has promising efficacy and safety in patients with metastatic colorectal cancer. We aimed to establish whether SOX plus bevacizumab is non-inferior to mFOLFOX6 (modified regimen of leucovorin, fluorouracil, and oxaliplatin) plus bevacizumab as first-line chemotherapy for metastatic colorectal cancer.
We undertook an open-label, non-inferiority, randomised phase 3 trial in 82 sites in Japan. We enrolled individuals aged 20-80 years who had metastatic colorectal cancer, had an Eastern Cooperative Oncology Group performance status of 0 or 1, had assessable lesions, had received no previous chemotherapy or radiotherapy, could take drugs orally, and had adequate organ function. Eligible patients were randomly assigned (1:1) to receive either mFOLFOX6 plus bevacizumab (on day 1 of each 2-week cycle, 5 mg/kg intravenous infusion of bevacizumab and a simultaneous intravenous infusion of 85 mg/m(2) oxaliplatin, 200 mg/m(2)l-leucovorin, 400 mg/m(2) bolus fluorouracil, and 2400 mg/m(2) infusional fluorouracil) or SOX plus bevacizumab (on day 1 of each 3-week cycle, 7·5 mg/kg intravenous infusion of bevacizumab and 130 mg/m(2) intravenous infusion of oxaliplatin; assigned dose of S-1 twice a day from after dinner on day 1 to after breakfast on day 15, followed by 7-day break). Randomisation was done centrally with the minimisation method, with stratification by institution and whether postoperative adjuvant chemotherapy had been given. Participants, investigators, and data analysts were not masked to treatment assignment. The primary endpoint was progression-free survival (PFS), which was defined as the interval between enrolment and progressive disease (≥20% increase in sum of longest dimensions of target lesions from baseline, or appearance of new lesions) or death, whichever came first. The primary analysis was done by modified intention to treat. This trial is registered with the Japan Pharmaceutical Information Center, number JapicCTI-090699.
Between Feb 1, 2009, and March 31, 2011, 512 patients underwent randomisation. 256 patients assigned to receive SOX plus bevacizumab and 255 assigned to receive mFOLFOX6 plus bevacizumab were included in the primary analysis. Median PFS was 11·5 months (95% CI 10·7-13·2) in the group assigned to mFOLFOX6 plus bevacizumab and 11·7 months (10·7-12·9) in the group assigned to SOX plus bevacizumab (HR 1·04, 95% CI 0·86-1·27; less than non-inferiority margin of 1·33, pnon-inferiority=0·014). The most common haematological adverse events of grade 3 or higher were leucopenia (21 [8%] of 249 patients given mFOLFOX6 plus bevacizumab included in safety analysis vs six [2%] of 250 given SOX plus bevacizumab; p=0·0029) and neutropenia (84 [34%] vs 22 [9%]; p<0·0001). Grade 3 or higher anorexia (13 [5%] vs three [1%]; p=0·019) and diarrhoea (23 [9%] vs seven [3%]; p=0·0040) were significantly more common in patients given SOX plus bevacizumab than in those given mFOLFOX6 plus bevacizumab. We recorded seven treatment-related deaths (three in the group given mFOLFOX6 plus bevacizumab; four in that given SOX plus bevacizumab).
SOX plus bevacizumab is non-inferior to mFOLFOX6 plus bevacizumab with respect to PFS as first-line treatment for metastatic colorectal cancer, and could become standard treatment in Asian populations.
The lancet oncology 11/2013; · 14.47 Impact Factor
[show abstract][hide abstract] ABSTRACT: We retrospectively examined the efficacy and safety of S-1 alone or S-1 plus cisplatin (SP) for elderly patients with advanced gastric cancer because the benefit of adding cisplatin in these patients still remains unclear.
Among 175 patients aged 70 years or older who received S-1 alone or SP as a first-line therapy between April 2000 and November 2010 at our institution, 104 patients who met eligibility criteria were examined. We investigated safety and efficacy of S-1 and SP.
Among these 104 patients, 73 patients received S-1 and 31 patients received SP. The median age was 75 years in the S-1 group and 74 years in the SP group. The response rate was 26.3 % in the S-1 group and 44.0 % in the SP group. Major grade 3 or higher adverse events were observed as follows (S-1 vs. SP): nausea (1.4 vs. 16.1 %), anorexia (16.4 vs. 41.9 %), neutropenia (4.1 vs. 35.5 %), and febrile neutropenia (0 vs. 9.7 %). The median overall survival (OS) was 10.4 months in the S-1 group and 17.8 months in the SP group. Treatment of SP and histology of intestinal type were detected as independent, good prognostic factors in multivariate analysis.
SP might improve OS with some added toxicity compared to S-1 alone in elderly patients with advanced gastric cancer.
Journal of Cancer Research and Clinical Oncology 10/2013; · 2.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: Aim: The use of weekly paclitaxel (wPTX) has become a common practice as second-line chemotherapy in Japanese patients with advanced gastric cancer. The aim of the present study was to assess the efficacy of wPTX.
We retrospectively analyzed data from 229 patients with advanced gastric cancer who received wPTX as second-line chemotherapy between March 2001 and January 2011 at our hospital. Patients received PTX at a dose of 80 mg/m(2) on days 1, 8, 15 of a 28-day cycle. Response and survival were evaluated.
The overall response rate was 12.5% in 96 patients who had measurable lesions that were assessable for response. In 107 patients who had malignant ascites, the response rate for therapy of ascites was 38.3%. The median progression-free survival was 3.6 months, and the median overall survival was 6.3 months. Multivariate analysis revealed that the number of metastatic sites [hazard ratio (HR)=1.56, p=0.009], bone metastasis (HR=2.11, p=0.006), ascites (HR 1.75, p<0.001), and the presence of the primary lesion (HR=1.77, p<0.001) were independent prognostic factors of poor survival.
wPTX is an effective regimen for advanced gastric cancer refractory to first-line chemotherapy.
Anticancer research 10/2013; 33(10):4547-4552. · 1.71 Impact Factor
[show abstract][hide abstract] ABSTRACT: RO5126766, a highly selective dual Raf and MEK inhibitor, is a first-in-class tandem mitogen-activated protein kinase signaling pathway inhibitor. The objectives of this phase I study were to determine maximum-tolerated dose (MTD) and to evaluate safety, pharmacokinetics (PK), pharmacodynamics (PD), and anti-tumor activity of RO5126766 in Japanese patients with advanced solid tumors.
Patients received a single oral dose of RO5126766 (0.8, 1.2, 1.8, or 2.25 mg) followed by continuous once-daily dosing at the same dosage in 28-day cycles. A 3 + 3 dose-escalation design was used. PD was evaluated by pMEK and pERK inhibition in peripheral blood mononuclear cells (PBMCs).
A total of 12 patients were enrolled in cohorts of 0.8, 1.2, 1.8, and 2.25 mg/day. In the dose range tested, no dose-limiting toxicity was observed, and therefore, MTD was not defined. Main adverse events included acneiform dermatitis, creatine phosphokinase elevation, and ocular disorders. The plasma exposure of RO5126766 appeared to increase in a dose-proportional manner with a long plasma half-life (t 1/2) of 45.8-93.7 h. Following multiple dose administration, a steady-state condition was reached by Cycle 1 Day 8 (240 h). The inhibitory effects of RO5126766 on both pERK and pMEK in PBMCs increased in a dose-dependent manner. Five out of 12 patients achieved stable diseases, including a melanoma case with over 20 % shrinkage.
RO5126766 has a manageable safety profile up to 2.25 mg/day once daily with a favorable PK/PD profile in Japanese patients with advanced solid tumors.
Cancer Chemotherapy and Pharmacology 07/2013; · 2.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: BACKGROUND: The KRAS mutation has been associated with resistance to cetuximab, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody, in metastatic colorectal cancer (mCRC). However, the predictive biomarkers of cetuximab resistance in KRAS wild-type mCRC remain unknown except BRAF, NRAS, and PIK3CA exon 20. The objective of the study is to study the impact of EGFR L2 mutations on resistance to cetuximab in KRAS wild-type patients. PATIENTS AND METHODS: A total of 247 mCRC patients were screened for KRAS status at the National Cancer Center Hospital between September 2008 and April 2010. We analyzed the EGFR L2 domain mutation status in KRAS wild type and in the patients treated with cetuximab-based therapy. RESULTS: There were 136 patients with wild-type KRAS (55 %). Sixty-five patients were analyzed for the L2 domain mutation status, and all patients received cetuximab-based therapy. One patient who had a mutation at exon 9 showed a partial response to cetuximab plus irinotecan. CONCLUSION: Mutation of the EGFR L2 domain was analyzed in mCRC patients. Our findings do not provide sufficient evidence that EGFR L2 domain mutation is correlated with resistance to cetuximab.
Journal of Cancer Research and Clinical Oncology 05/2013; · 2.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: Direct sequencing (DS) has often been used for detection of v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations. High-resolution melting analysis (HRMA) is another method to detect mutations by using a light scanner, and is more rapid, lower in cost, and more sensitive than DS. We confirmed correspondence between DS and HRMA for KRAS mutation detection in colorectal cancer (CRC).
From 102 patients with CRC, intended to receive cetuximab treatment at the National Cancer Center Hospital between September 2008 and July 2009, formalin-fixed paraffin-embedded tissues were retrospectively analyzed for KRAS status using HRMA and DS. Cetuximab efficacy was evaluated.
Success rates of analysis by DS and HRMA were 100 out of the 102 patients (98.0%) and 99 out of the 102 patients (97.1%), respectively. The cases which failed by one method were analyzed by the other. KRAS mutant-type was detected by DS in 47 out of 100 samples (47.0%), and by HRMA in 45 out of 99 samples (45.5%). The concordance between the two methods was 94.8%. Forty-six out of the 53 patients with wild-type KRAS, as detected by DS received cetuximab and the response and disease control rates were 19.6% and 63.0%, respectively. With a median follow-up of 8.8 months, the median progression-free survival was 5.6 months and median overall survival was 11.1 months. The efficacy of two discordant cases which received cetuximab showed that the best responses were stable disease and progressive disease in one each, progression-free survival was 2.9 and 1.1 months and overall survival was 5.3 and 1.2 months, respectively.
HRMA is a useful optional method for detection of KRAS mutations in CRC in light of accuracy, cost performance and rapidity.
Anticancer research 05/2013; 33(5):2129-34. · 1.71 Impact Factor
[show abstract][hide abstract] ABSTRACT: PURPOSE: LY2334737 is an oral gemcitabine prodrug. This Phase I study assessed the safety and tolerability of LY2334737 in Japanese patients with solid tumors and evaluated pharmacokinetics (PK), pharmacodynamics, and antitumor activity. METHODS: Patients with advanced/metastatic solid tumors received escalating doses of LY2334737 once daily for 14 days, followed by a 7-day drug-free period. Cycles were repeated until discontinuation criteria were met. RESULTS: Of 13 patients treated, 3 received 20 mg/day, 6 received 30 mg/day, 4 received 40 mg/day. On the 40 mg dose, 3 patients experienced dose-limiting toxicities (DLTs): hepatic toxicities (e.g., Grade [G]3/4 transaminase and G1-3 bilirubin elevation) and G4 thrombocytopenia; all 3 showed features of disseminated intravascular coagulation. One additional DLT occurred on the 30 mg dose (G3 transaminase elevation). Exploratory pharmacogenetic analyses identified a genetic variation in the CES2 gene potentially associated with these DLTs. PK data showed no clear relationship between the AUC of gemcitabine and its incorporation into leukocyte DNA; 2 of the 3 DLT patients had high incorporation. Two patients (30 mg/day) achieved stable disease with progression-free survival lasting 135 and 155 days. CONCLUSIONS: LY2334737 was tolerated by Japanese patients up to 30 mg/day. The toxicities observed at the 40 mg dose may require the development of alternative dosing schedules.
Cancer Chemotherapy and Pharmacology 04/2013; · 2.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: BACKGROUND: Sorafenib inhibits several receptor tyrosine kinases involved in tumor progression and angiogenesis. S-1, an oral fluorouracil antitumor drug, plus cisplatin (CDDP) is the standard regimen for advanced gastric adenocarcinoma (AGC) in Japan. The purpose of this phase I study was to evaluate the safety, pharmacokinetics, and preliminary efficacy of sorafenib in combination with S-1 plus CDDP. METHODS: Patients with histologically confirmed previously untreated AGC were evaluated for eligibility and treated with sorafenib (400 mg bid, days 1-35), S-1 (40 mg/m(2) bid, days 1-21), and CDDP (60 mg/m(2), day 8). Treatment was continued until disease progression or unacceptable toxicity. Pharmacokinetics for sorafenib, 5-FU, and CDDP were investigated in cycle 1. RESULTS: Thirteen patients were enrolled and received at least one dose of the study treatment. No specific or serious adverse event was newly reported in this study. Five patients had partial response and 8 had stable disease as the best response. Pharmacokinetic analysis showed no significant differences in the exposures of sorafenib when administered alone or in combination with S-1 and CDDP. CONCLUSIONS: The present phase I study demonstrates the acceptable toxicity and preliminary efficacy of combined treatment with S-1, CDDP, and sorafenib.
[show abstract][hide abstract] ABSTRACT: BACKGROUND: There have been no reports on the incidence, characteristics, treatment outcomes, and prognosis of inoperably advanced or recurrent adenocarcinoma of the esophagogastric junction (AEGJ) in Japan. METHODS: We investigated the clinicopathological characteristics, treatment outcomes, and prognosis for 816 patients with esophagogastric junctional and gastric adenocarcinoma who received first-line chemotherapy between 2004 and 2009. RESULTS: Of 816 patients, 82 (10 %) had AEGJ. The patients with AEGJ had significantly more lung and lymph node metastasis, but less peritoneal metastasis, than those with gastric adenocarcinoma (GAC). The objective response rate to first-line chemotherapy was 23.3 % for patients with AEGJ and 22.6 % in patients with GAC (p = 0.90). The median survival was 13.0 months in AEGJ and 11.8 months in GAC (p = 0.445). In no patient was tumor site a significant prognostic factor (p = 0.472). In patients with AEGJ, ECOG PS ≥ 2, presence of liver metastasis, and absence of lung metastasis were significantly associated with poor prognosis. CONCLUSIONS: No significant differences were observed in treatment outcomes between advanced AEGJ and GAC. Therefore, the same chemotherapy regimen can be given as a treatment arm in future Japanese clinical trials to both patients with inoperably advanced or recurrent AEGJ and those with GAC.
[show abstract][hide abstract] ABSTRACT: The gene amplification of ribosomal protein S6 kinase 1 and 2 (S6K1 and S6K2) and its clinical relevance in gastric cancer remain unclear.
A comparative genomic hybridization analysis and DNA copy number assay were performed for nine cancer cell lines. The gene amplification of S6K1 and S6K2 were determined using a DNA copy number assay of 213 gastric cancer tissues.
S6K1 and S6K2 amplifications were observed in one and three cancer cell lines, respectively. No amplification of S6K1 was detected in the gastric cancer tissues, while S6K2 amplification was observed in 4.7% of the gastric carcinoma tissues. Patients with stage IV gastric cancer whose tumors exhibited amplification had a significantly shorter overall survival.
S6K2 amplification was frequently observed in gastric cancer and was related to a poor prognosis. Our findings may provide novel insight into the dysregulation of mammalian target of rapamycin signaling by S6K2 amplification in gastric cancer.
Anticancer research 02/2013; 33(2):469-75. · 1.71 Impact Factor
[show abstract][hide abstract] ABSTRACT: Although bevacizumab-related hypertension has been reported as a predictive marker of therapy efficacy, an association between proteinuria and efficacy has not been reported.
Eighty-two consecutive patients with metastatic colorectal cancer treated with bevacizumab as first-line treatment between July 2007 and April 2009 were examined.
Seventy-one patients were included in the analysis set. Proteinuria occurred in 29 patients: Grade 1 in 15 patients and grade 2 in 14 patients; no grade 3 or higher proteinuria was observed. The response rate did not increase with the severity of proteinuria (p=0.307). The median progression-free survival was 17.8 months in cases with grade 2 proteinuria, 16.0 months in those with grade 1 proteinuria, and 10.4 months in those with grade 0 proteinuria (p=0.030). In multivariate analysis with a time-dependent adjustment, there was no correlation between severity of proteinuria and survival.
Bevacizumab-related proteinuria was not a predictive marker for patients with colorectal cancer treated with first-line bevacizumab.
Anticancer research 01/2013; 33(1):309-16. · 1.71 Impact Factor
[show abstract][hide abstract] ABSTRACT: Discontinuation of oxaliplatin-containing regimens is sometimes necessary due to hypersensitivity reactions for which effective countermeasures have not yet been identified.
We retrospectively reviewed cases in which hypersensitivity reactions developed in 623 patients treated with oxaliplatin for colorectal cancer. Clinical outcomes of patients who underwent oxaliplatin rechallenge with rechallenge protocol (STEP 1: hydrocortisone, chlorpheniramine, and/or ranitidine; STEP 2: hydrocortisone with an escalating dose to 500 mg, and/or prolonged administration time of oxaliplatin; and STEP 3: STEP 2 plus a subcutaneous injection of epinephrine) were examined.
Out of 623 patients, 126 (20.2%) patients developed hypersensitivity reactions. Out of these 126 patients, 99 (78.6%) underwent oxaliplatin rechallenge. As the initial oxaliplatin rechallenge, 19 patients received subsequent treatment without the rechallenge protocol and 80 patients received oxaliplatin with the rechallenge protocol of STEP 1 (n=64), STEP 2 (n=15), and STEP 3 (n=1). The median number of oxaliplatin rechallenges was 3 (range=1 to 29). The reason for treatment discontinuation was disease progression in 55 patients (56%) and hypersensitivity reactions in 21 patients (21%). Overall hypersensitivity reactions after rechallenge were observed in 59%, with grade 3/4 in 6%.
The rechallenge protocol is an effective treatment option for patients with oxaliplatin hypersensitivity reactions.
Anticancer research 12/2012; 32(12):5521-6. · 1.71 Impact Factor
[show abstract][hide abstract] ABSTRACT: Our aim was to investigate both the prevalence of MET amplification in gastric cancer as well as the potential of this genetic alteration to serve as a therapeutic target in gastric cancer. MET amplification was assessed by initial screening with a PCR-based copy number assay followed by confirmatory FISH analysis in formalin-fixed, paraffin-embedded specimens of gastric cancer obtained at surgery. The effects of MET tyrosine kinase inhibitors (MET-TKIs) in gastric cancer cells with or without MET amplification were also examined. The median MET copy number in 266 cases of gastric cancer was 1.7, with a range of 0.41 to 21.3. We performed FISH analysis for the 15 cases with the highest MET copy numbers. MET amplification was confirmed in the four assessable cases with a MET copy number of at least 4, whereas MET amplification was not detected in those with a gene copy number of less than 4. The prevalence of MET amplification was thus 1.5% (4 out of 266 cases). Inhibition of MET by MET-TKIs resulted in the induction of apoptosis accompanied by attenuation of downstream MET signaling in gastric cancer cell lines with MET amplification but not in those without this genetic change. MET amplification identifies a small but clinically important subgroup of gastric cancer patients who are likely to respond to MET-TKIs. Furthermore, screening with a PCR-based copy number assay is an efficient way to reduce the number of patients requiring confirmation of MET amplification by FISH analysis.
[show abstract][hide abstract] ABSTRACT: A double-blind, placebo-controlled study evaluating the efficacy and safety of vitamin K1 ointment for the treatment of patients with cetuximab-induced acneiform eruption has started. Vitamin K1 ointment and placebo are applied twice daily for 8 consecutive weeks after the development of acneiform eruptions. Vitamin K1 ointment is applied in the middle of one side (face, neck or chest) and placebo is applied to the other side. The primary endpoint is the regression rate of acneiform eruptions on right- and left-side lesions in the same patient, compared with baseline at the final evaluation in the 10-week trial. The secondary endpoints include adverse events of acneiform eruption and other adverse events.
Japanese Journal of Clinical Oncology 11/2012; · 1.90 Impact Factor