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Featured researches published by Koji Oba.


JAMA | 2010

Benefit of adjuvant chemotherapy for resectable gastric cancer: a meta-analysis.

Xavier Paoletti; Koji Oba; Tomasz Burzykowski; Stefan Michiels; Yasuo Ohashi; Jean-Pierre Pignon; Philippe Rougier; Junichi Sakamoto; Daniel J. Sargent; Mitsuru Sasako; Eric Van Cutsem; Marc Buyse

CONTEXT Despite potentially curative resection of stomach cancer, 50% to 90% of patients die of disease relapse. Numerous randomized clinical trials (RCTs) have compared surgery alone with adjuvant chemotherapy, but definitive evidence is lacking. OBJECTIVES To perform an individual patient-level meta-analysis of all RCTs to quantify the potential benefit of chemotherapy after complete resection over surgery alone in terms of overall survival and disease-free survival, and to further study the role of regimens, including monochemotherapy; combined chemotherapy with fluorouracil derivatives, mitomycin C, and other therapies but no anthracyclines; combined chemotherapy with fluorouracil derivatives, mitomycin C, and anthracyclines; and other treatments. DATA SOURCES Data from all RCTs comparing adjuvant chemotherapy with surgery alone in patients with resectable gastric cancer. We searched MEDLINE (up to 2009), the Cochrane Central Register of Controlled Trials, the National Institutes of Health trial registry, and published proceedings from major oncologic and gastrointestinal cancer meetings. STUDY SELECTION All RCTs closed to patient recruitment before 2004 were eligible. Trials testing radiotherapy; neoadjuvant, perioperative, or intraperitoneal chemotherapy; or immunotherapy were excluded. Thirty-one eligible trials (6390 patients) were identified. DATA EXTRACTION As of 2010, individual patient data were available from 17 trials (3838 patients representing 60% of the targeted data) with a median follow-up exceeding 7 years. RESULTS There were 1000 deaths among 1924 patients assigned to chemotherapy groups and 1067 deaths among 1857 patients assigned to surgery-only groups. Adjuvant chemotherapy was associated with a statistically significant benefit in terms of overall survival (hazard ratio [HR], 0.82; 95% confidence interval [CI], 0.76-0.90; P < .001) and disease-free survival (HR, 0.82; 95% CI, 0.75-0.90; P < .001). There was no significant heterogeneity for overall survival across RCTs (P = .52) or the 4 regimen groups (P = .13). Five-year overall survival increased from 49.6% to 55.3% with chemotherapy. CONCLUSION Among the RCTs included, postoperative adjuvant chemotherapy based on fluorouracil regimens was associated with reduced risk of death in gastric cancer compared with surgery alone.


European Journal of Cancer | 2010

Benefit of adjuvant chemotherapy for resectable gastric cancer: A meta-analysis

Xavier Paoletti; Koji Oba; Tomasz Burzykowski; Stefan Michiels; Yasuo Ohashi; Jean-Pierre Pignon; Philippe Rougier; Junichi Sakamoto; Daniel J. Sargent; Mitsuru Sasako; Eric Van Cutsem; Marc Buyse; Seiichiro Yamamoto; Kenichi Yoshimura; Yung Jue Bang; Harry Bleiberg; Catherine Delbaldo; Satoshi Morita; Carmelo Pozzo; Steven R. Alberts; Emilio Bajetta; Jacqueline Benedetti; Franck Bonnetain; Olivier Bouché; R. Charles Coombes; Maria Di Bartolomeo; Juan J. Grau; Juan Carlos García-Valdecasas; Josep Fuster; James E. Krook

CONTEXT Despite potentially curative resection of stomach cancer, 50% to 90% of patients die of disease relapse. Numerous randomized clinical trials (RCTs) have compared surgery alone with adjuvant chemotherapy, but definitive evidence is lacking. OBJECTIVES To perform an individual patient-level meta-analysis of all RCTs to quantify the potential benefit of chemotherapy after complete resection over surgery alone in terms of overall survival and disease-free survival, and to further study the role of regimens, including monochemotherapy; combined chemotherapy with fluorouracil derivatives, mitomycin C, and other therapies but no anthracyclines; combined chemotherapy with fluorouracil derivatives, mitomycin C, and anthracyclines; and other treatments. DATA SOURCES Data from all RCTs comparing adjuvant chemotherapy with surgery alone in patients with resectable gastric cancer. We searched MEDLINE (up to 2009), the Cochrane Central Register of Controlled Trials, the National Institutes of Health trial registry, and published proceedings from major oncologic and gastrointestinal cancer meetings. STUDY SELECTION All RCTs closed to patient recruitment before 2004 were eligible. Trials testing radiotherapy; neoadjuvant, perioperative, or intraperitoneal chemotherapy; or immunotherapy were excluded. Thirty-one eligible trials (6390 patients) were identified. DATA EXTRACTION As of 2010, individual patient data were available from 17 trials (3838 patients representing 60% of the targeted data) with a median follow-up exceeding 7 years. RESULTS There were 1000 deaths among 1924 patients assigned to chemotherapy groups and 1067 deaths among 1857 patients assigned to surgery-only groups. Adjuvant chemotherapy was associated with a statistically significant benefit in terms of overall survival (hazard ratio [HR], 0.82; 95% confidence interval [CI], 0.76-0.90; P < .001) and disease-free survival (HR, 0.82; 95% CI, 0.75-0.90; P < .001). There was no significant heterogeneity for overall survival across RCTs (P = .52) or the 4 regimen groups (P = .13). Five-year overall survival increased from 49.6% to 55.3% with chemotherapy. CONCLUSION Among the RCTs included, postoperative adjuvant chemotherapy based on fluorouracil regimens was associated with reduced risk of death in gastric cancer compared with surgery alone.


Hypertension | 2008

Effects of Candesartan Compared With Amlodipine in Hypertensive Patients With High Cardiovascular Risks: Candesartan Antihypertensive Survival Evaluation in Japan Trial

Toshio Ogihara; Kazuwa Nakao; Tsuguya Fukui; Kohshiro Fukiyama; Kenji Ueshima; Koji Oba; Tosiya Sato; Takao Saruta

The Candesartan Antihypertensive Survival Evaluation in Japan Trial was designed to compare the long-term effects of the angiotensin II receptor blocker candesartan and the calcium channel blocker amlodipine on the incidence of cardiovascular events, represented as a composite of sudden death and cerebrovascular, cardiac, renal, and vascular events in high-risk Japanese hypertensive patients. We conducted a prospective, randomized, open-label study with blinded assessment of the end point in 4728 Japanese hypertensive patients (mean age: 63.8 years; mean body mass index: 24.6 kg/m2). Patients were followed for an average of 3.2 years. Blood pressure was well controlled with both treatment-based regimens (systolic blood pressure/diastolic blood pressure: 136.1/77.3 mm Hg for candesartan-based regimens and 134.4/76.7 mm Hg for amlodipine-based regimens after 3 years). Primary cardiovascular events occurred in 134 patients with both the candesartan- and amlodipine-based regimens. The 2 treatment-based regimens produced no significant differences in cardiovascular morbidity or mortality in the high-risk Japanese hypertensive patients (hazard ratio: 1.01; 95% CI: 0.79 to 1.28; P=0.969). In each primary end point category, there was no significant difference between the 2 treatment-based regimens. New-onset diabetes occurred in fewer patients taking candesartan (8.7/1000 person-years) than in those taking amlodipine (13.6/1000 person-years), which resulted in a 36% relative risk reduction (hazard ratio: 0.64; 95% CI: 0.43 to 0.97; P=0.033). We disclosed that candesartan-based and amlodipine-based regimens produced no statistical differences in terms of the primary cardiovascular end point, whereas candesartan prevented new-onset diabetes more effectively than amlodipine.


European Journal of Cancer | 2013

Role of chemotherapy for advanced/recurrent gastric cancer: An individual-patient-data meta-analysis

Koji Oba; Xavier Paoletti; Yung-Jue Bang; Harry Bleiberg; Tomasz Burzykowski; Nozomu Fuse; Stefan Michiels; Satoshi Morita; Yasuo Ohashi; Jean-Pierre Pignon; Philippe Rougier; Georges Pompidou; Junichi Sakamoto; Daniel J. Sargent; Mitsuru Sasako; Kohei Shitara; Akira Tsuburaya; Eric Van Cutsem; Marc Buyse

We conducted an individual-patient-data meta-analysis of the efficacy of chemotherapy on overall survival (OS) and progression-free survival (PFS) in advanced/recurrent gastric cancer (AGC). Our primary research question was whether the experimental arms of the trials included in the meta-analysis showed a benefit as compared with their corresponding control arms. MEDLINE (up to 2010), Cochrane Central Register of Controlled Trials, National Institutes of Health (NIH) trial registry and proceedings of major oncologic and gastrointestinal cancer meetings were searched. Randomised controlled trials for AGC closed to patient accrual before the end of 2006 were eligible. As of December 2010, individual patient data were available from 22 trials (4245 patients, representing 47% of the targeted data) of 55 eligible trials. The overall comparison of experimental arms with the corresponding control arms showed statistically significant differences in terms of both OS and PFS. Hazard ratio was 0.88 (95% confidence interval 0.82-0.94, P<0.0001) for OS and 0.81 (0.76-0.88, P<0.0001) for PFS. The results of the sub-analysis of adding a given chemotherapeutic agent to any chemotherapy confirm the results of the overall analysis, with a hazard reduction of 11% for OS (P<0.01) and 26% for PFS (P<0.0001). This meta-analysis of individual patient data shows that the additions of experimental chemotherapeutic agents to pre-existing control or standard regimens have produced a modest improvement in OS and PFS. Median survival remained below 1 year for all investigated chemotherapy regimens and none emerged as a clear standard.


Journal of the National Cancer Institute | 2013

Disease-Free Survival as a Surrogate for Overall Survival in Adjuvant Trials of Gastric Cancer: A Meta-Analysis

Koji Oba; Xavier Paoletti; Steven R. Alberts; Yung Jue Bang; Jacqueline Benedetti; Harry Bleiberg; Paul J. Catalano; Florian Lordick; Stefan Michiels; Satoshi Morita; Yasuo Ohashi; Jean-Pierre Pignon; Philippe Rougier; Mitsuru Sasako; Junichi Sakamoto; Daniel J. Sargent; Kohei Shitara; Eric Van Cutsem; Marc Buyse; Tomasz Burzykowski

BACKGROUND In investigations of the effectiveness of surgery and adjuvant chemotherapy for gastric cancers, overall survival (OS) is considered the gold standard endpoint. However, the disadvantage of using OS as the endpoint is that it requires an extended follow-up period. We sought to investigate whether disease-free survival (DFS) is a valid surrogate for OS in trials of adjuvant chemotherapy for gastric cancer. METHODS The GASTRIC group initiated a meta-analysis of individual patient data collected in randomized clinical trials comparing adjuvant chemotherapy vs surgery alone for patients with curatively resected gastric cancer. Surrogacy of DFS was assessed through the correlation between the endpoints as well as through the correlation between the treatment effects on the endpoints. External validation of the prediction based on DFS was also evaluated. RESULTS Individual patient data from 14 randomized clinical trials that included a total of 3288 patients were analyzed. The rank correlation coefficient between DFS and OS was 0.974 (95% confidence interval [CI] = 0.971 to 0.976). The coefficient of determination between the treatment effects on DFS and on OS was as high as 0.964 (95% CI = 0.926 to 1.000), and the surrogate threshold effect based on adjusted regression analysis was 0.92. In external validation, the six hazard ratios for OS predicted according to DFS were in very good agreement with those actually observed for OS. CONCLUSIONS DFS is an acceptable surrogate for OS in trials of cytotoxic agents for gastric cancer in the adjuvant setting.


Lancet Oncology | 2014

Sequential paclitaxel followed by tegafur and uracil (UFT) or S-1 versus UFT or S-1 monotherapy as adjuvant chemotherapy for T4a/b gastric cancer (SAMIT): a phase 3 factorial randomised controlled trial

Akira Tsuburaya; Kazuhiro Yoshida; Michiya Kobayashi; Shigefumi Yoshino; Masazumi Takahashi; Nobuhiro Takiguchi; Kazuaki Tanabe; Naoto Takahashi; Hiroshi Imamura; Naokuni Tatsumoto; Akinori Hara; Kazuhiro Nishikawa; Ryoji Fukushima; Isao Nozaki; Hiroshi Kojima; Yumi Miyashita; Koji Oba; Marc Buyse; Satoshi Morita; Junichi Sakamoto

BACKGROUND The prognosis for locally advanced gastric cancer is poor despite advances in adjuvant chemotherapy. We did the Stomach cancer Adjuvant Multi-Institutional group Trial (SAMIT) to assess the superiority of sequential treatment (paclitaxel then tegafur and uracil [UFT] or paclitaxel then S-1) compared with monotherapy (UFT or S-1) and also the non-inferiority of UFT compared with S-1. METHODS We did this randomised phase 3 trial with a two-by-two factorial design at 230 hospitals in Japan. We enrolled patients aged 20-80 years with T4a or T4b gastric cancer, who had had D2 dissection and a ECOG performance score of 0-1. Patients were randomly assigned to one of four treatment groups with minimisation for tumour size, lymph node metastasis, and study site. Patients received UFT only (267 mg/m(2) per day), S-1 only (80 mg/m(2) per day) for 14 days, with a 7-day rest period or three courses of intermittent weekly paclitaxel (80 mg/m(2)) followed by either UFT, or S-1. Treatment lasted 48 weeks in monotherapy groups and 49 weeks in the sequential treatment groups. The primary endpoint was disease-free survival assessed by intention to treat. We assessed whether UFT was non-inferior to S-1 with a non-inferiority margin of 1·33. This trial was registered at UMIN Clinical Trials Registry, number C000000082. FINDINGS We randomly assigned 1495 patients between Aug 3, 2004, and Sept 29, 2009. 374 patients were assigned to receive UFT alone, 374 to receive S-1 alone, 374 to received paclitaxel then UFT, and 373 to receive paclitaxel then S-1. We included 1433 patients in the primary analysis after at least 3 years of follow-up (359, 364, 355, and 355 in each group respectively). Protocol treatment was completed by 215 (60%) patients in the UFT group, 224 (62%) in the S-1 group, 242 (68%) in the paclitaxel then UFT group, and 250 (70%) in the paclitaxel then S-1 group. 3-year disease-free survival for monotherapy was 54·0% (95% CI 50·2-57·6) and that of sequential treatment was 57·2% (53·4-60·8; hazard ratio [HR] 0·92, 95% CI 0·80-1·07, p=0·273). 3-year disease-free survival for the UFT group was 53·0% (95% CI 49·2-56·6) and that of the S-1 group was 58·2% (54·4-61·8; HR 0·81, 95% CI 0·70-0·93, p=0·0048; pnon-inferiority=0·151). The most common grade 3-4 haematological adverse event was neutropenia (41 [11%] of 359 patients in the UFT group, 48 [13%] of 363 in the S-1 group, 46 [13%] of 355 in the paclitaxel then UFT group, and 83 [23%] of 356 in the paclitaxel then S-1 group). The most common grade 3-4 non-haematological adverse event was anorexia (21 [6%], 24 [7%], seven [2%], and 18 [5%], respectively). INTERPRETATION Sequential treatment did not improve disease-free survival, and UFT was not non-inferior to S-1 (and S-1 was superior to UFT), therefore S-1 monotherapy should remain the standard treatment for locally advanced gastric cancer in Japan. FUNDING Epidemiological and Clinical Research Information Network.


Rheumatology | 2015

The efficacy of tacrolimus in patients with interstitial lung diseases complicated with polymyositis or dermatomyositis

Takashi Kurita; Shinsuke Yasuda; Koji Oba; Toshio Odani; Michihito Kono; Kotaro Otomo; Yuichiro Fujieda; Kenji Oku; Toshiyuki Bohgaki; Olga Amengual; Tetsuya Horita; Tatsuya Atsumi

OBJECTIVE Interstitial lung diseases (ILDs) complicated with PM or DM are frequently aggressive and refractory to treatment. Recently some reports have suggested the potential benefit of tacrolimus for severe ILD complicated with PM/DM. However, little evidence has yet shown the efficacy of tacrolimus in these settings. The aim of this study was to evaluate the efficacy of tacrolimus as a treatment for PM-/DM-related ILD. METHODS This retrospective study comprised 49 previously untreated patients diagnosed as PM-/DM-related ILD admitted to Hokkaido University Hospital from January 2000 to July 2013. These patients were treated with tacrolimus plus conventional therapy or only with conventional therapy (prednisolone, i.v. CYC and/or ciclosporin). The primary endpoint was defined as the time to relapse or death of respiratory cause or a serious adverse event. The secondary endpoint was defined as the time from the initiation of immunosuppressive treatment to relapse or death of respiratory cause. Endpoints were compared by adjusted Cox regression model by using inverse probability of treatment weighting in order to reduce the impact of these selection biases and potential confounding factors. RESULTS After adjustment, the tacrolimus group (n = 25) had significantly longer event-free survival as compared with the conventional therapy group (n = 24). The weighted hazard ratio (HR) was 0.32 (95% CI 0.14, 0.75, P = 0.008). In addition, the tacrolimus group had significantly longer disease-free survival as compared with the conventional therapy group. The weighted HR was 0.25 (95% CI 0.10, 0.66, P = 0.005). CONCLUSION The addition of tacrolimus to conventional therapy significantly improved the prognosis of patients with PM-/DM-related ILD.


Journal of the National Cancer Institute | 2013

Progression-Free Survival as a Surrogate for Overall Survival in Advanced/Recurrent Gastric Cancer Trials: A Meta-Analysis

Xavier Paoletti; Koji Oba; Yung Jue Bang; Harry Bleiberg; Narikazu Boku; Olivier Bouché; Paul J. Catalano; Nozomu Fuse; Stefan Michiels; Markus Moehler; Satoshi Morita; Yasuo Ohashi; Atsushi Ohtsu; Arnaud Roth; Philippe Rougier; Junichi Sakamoto; Daniel J. Sargent; Mitsuru Sasako; Kohei Shitara; Peter C. Thuss-Patience; Eric Van Cutsem; Tomasz Burzykowski; Marc Buyse

The traditional endpoint for assessing efficacy of chemotherapies for advanced/recurrent gastric cancer is overall survival (OS), but OS requires prolonged follow-up. We investigated whether progression-free survival (PFS) is a valid surrogate for OS. Using individual patient data from the GASTRIC meta-analysis, surrogacy of PFS was assessed through the correlation between the endpoints and through the correlation between the treatment effects on the endpoints. External validation of the prediction based on PFS was also evaluated. Individual data from 4069 patients in 20 randomized trials were analyzed. The rank correlation coefficient between PFS and OS was 0.853 (95% confidence interval [CI] = 0.852 to 0.854). The R (2) between treatment effects on PFS and on OS was 0.61 (95% CI = 0.04 to 1.00). Treatment effects on PFS and on OS were only moderately correlated, and we could not confirm the validity of PFS as a surrogate endpoint for OS in advanced/recurrent gastric cancer.


British Journal of Cancer | 2007

An individual patient data meta-analysis of adjuvant therapy with uracil–tegafur (UFT) in patients with curatively resected rectal cancer

Junichi Sakamoto; Chikuma Hamada; S Yoshida; S Kodaira; M Yasutomi; Tatsuya Kato; Koji Oba; Hiroaki Nakazato; Shigetoyo Saji; Yasuo Ohashi

Uracil–Tegafur (UFT), an oral fluorinated pyrimidine chemotherapeutic agent, has been used for adjuvant chemotherapy in curatively resected colorectal cancer patients. Past trials and meta-analyses indicate that it is somewhat effective in extending survival of patients with rectal cancer. The objective of this study was to perform a reappraisal of randomised clinical trials conducted in this field. We designed an individual patient-based meta-analysis of relevant clinical trials to examine the benefit of UFT for curatively resected rectal cancer in terms of overall survival (OS), disease-free survival (DFS), and local relapse-free survival (LRFS). We analysed individual patient data of five adjuvant therapy randomised clinical trials for rectal cancer, which met the predetermined inclusion criteria. These five trials had a combined total of 2091 patients, UFT as adjuvant chemotherapy compared to surgery-alone, 5-year follow-up, intention-to-treat-based analytic strategy, and similar endpoints (OS and DFS). In a pooled analysis, UFT had significant advantage over surgery-alone in terms of both OS (hazard ratio, 0.82; 95% confidence interval (CI), 0.70–0.97; P=0.02) and DFS (hazard ratio, 0.73; 95%CI, 0.63–0.84; P<0.0001). This individual patient-based meta-analysis demonstrated that oral UFT significantly improves both OS and DFS in patients with curatively resected rectal cancer.


Japanese Journal of Clinical Oncology | 2011

Prospective Phase II Study of FOLFIRI for mCRC in Japan, Including the Analysis of UGT1A1*28/*6 Polymorphisms

Yusuke Okuyama; Shoichi Hazama; Hiroshi Nozawa; Michiya Kobayashi; Kenichi Takahashi; Koshi Fujikawa; Takeshi Kato; Naoki Nagata; Humihiko Kimura; Koji Oba; Junichi Sakamoto; Hideyuki Mishima

OBJECTIVES This is the first phase II study to evaluate the efficacy and tolerability of the first-line FOLFIRI, as well as the influence of uridine diphosphate glucuronosyl transferase 1, family polypeptide A1 gene (UGT1A1) 28/6 polymorphism, in Japanese metastatic colorectal cancer patients. METHODS Fifty-two patients were enrolled in this study and were administrated FOLFIRI (irinotecan; 150 mg/m(2)) as first-line chemotherapy. Thirty-nine patients accepted the evaluation of UGT1A1 genotypes. In patients with UGT1A1 28 homozygosity, the starting dose was reduced (100 mg/m(2)) according to the Food and Drug Administration recommendation and our previous phase I study. RESULTS After a median follow-up period of 22 months, complete response was achieved in 1.9%, partial response in 38.5 %, stable disease in 51.9% and progressive disease in 3.9%. The overall response rate was 40.4%, the disease control rate was 92.3% and the median overall survival time was 22.3 months. The major toxicity was grade 3-4 neutropenia in 44.2%. There was no definite relation between UGT1A1 28, 6 polymorphisms and toxicity. However, homozygosity for UGT1A1 28 or UGT1A1 6 and double heterozygosity for both UGT1A1 28 and UGT1A1 6 were significantly associated with severe neutropenia in metastatic colorectal cancer patients (P< 0.001). CONCLUSIONS FOLFIRI is effective and tolerable for Japanese metastatic colorectal cancer patients. Homozygosity for UGT1A1 28 or 6 and heterozygosity for both UGT1A1 28 and 6 are associated with severe neutropenia.

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Toru Aoyama

Yokohama City University

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