Hideyuki Akaza

BACKGROUND: Our previous case-control study revealed that the Japanese residents in Japan could be divided into those who are able to degrade daidzein, a soybean isoflavone, to equol and those without this ability, and that the incidence of prostate cancer is higher in the latter group. METHODS: We recently conducted a similar case-control study involving not only Japanese residents in Japan but also Korean residents in Korea. The incidence of prostate cancer in Korean residents is known to be close to that of Japanese residents in Japan. On the other hand, American residents in the United States have a markedly higher incidence of prostate cancer as compared to Japanese residents in Japan. RESULTS: The number of subjects was 295 in Japan (133 patients and 162 controls), 122 in Korea (61 patients and 61 controls) and 45 in the United States (24 patients and 21 controls). The percentage of equol producers among patients and controls was 29% and 46% in Japan (P = 0.004) and 30% and 59% in Korea (P = 0.001), respectively. The active isoflavone level was markedly lower and the percentage of equol producers was also lower (17% for patients and 14% for controls) for Americans as compared to the Japanese and Koreans. CONCLUSIONS: These results suggest that the ability of producing equol or equol itself is closely related to the lower incidence of prostate cancer. The results also suggest that a diet based on soybean isoflavones will be useful in preventing prostate cancer.

OBJECTIVE: This study aims to assess the efficacy and safety of sunitinib in Japanese patients with metastatic renal cell carcinoma (RCC). METHODS: Fifty-one Japanese patients with prior nephrectomy, 25 treatment-naive patients (first-line group) and 26 cytokine-refractory patients (pretreated group) were enrolled in this phase II trial. Patients received sunitinib 50 mg orally, once daily, in repeated 6-week cycles (4 weeks on treatment, 2 weeks off). The primary endpoint was RECIST-defined objective response rate (ORR) with tumour assessments every 6 weeks via computed tomography or magnetic resonance imaging. Toxicity was assessed regularly. In the primary efficacy analysis of the intent-to-treat (ITT) population, ORR and 95% confidence interval were calculated based on independent review. Secondary time-to-event endpoints, such as progression-free survival (PFS), were estimated using the Kaplan-Meier method. RESULTS: In the ITT population, ORR was 48.0% in the first-line group (after a median 4 cycles), 46.2% in the pretreated group (5 cycles) and 47.1% overall, with median times to tumour response of 7.1, 10.7 and 10.0 weeks, respectively. Median PFS was 46.0, 33.6 and 46.0 weeks, respectively. The most common treatment-related grade 3/4 adverse events and laboratory abnormalities were fatigue (20%), hand-foot syndrome (14%) and hypertension (12%), decreased platelet count (55%), decreased neutrophil count (51%), increased lipase (39%) and decreased lymphocyte count (33%). CONCLUSIONS: In Japanese patients with RCC, sunitinib is consistently effective and tolerable with similar risk/benefit as that in Western patients, though there was a trend toward greater antitumour efficacy and higher incidence of haematological adverse events in Japanese patients.

OBJECTIVES: To evaluate bicalutamide (Casodex) 80 mg as a component of maximum androgen blockade (MAB) in Japanese patients with previously untreated advanced prostate cancer. METHODS: 205 patients with previously untreated stage C/D prostate cancer were randomized (1:1) to receive once-daily bicalutamide 80 mg or placebo, each combined with a luteinizing hormone-releasing hormone (LHRH) agonist. Primary study variables were the 12 week prostate-specific antigen (PSA) normalization (i.e. PSA level <or=4 ng/ml) rate, the 12 week overall tumor response rate (proportion with a partial response or better) and the proportion of withdrawals due to adverse drug reactions (ADRs) at follow-up. This interim analysis was undertaken after a minimum of 6 months' follow-up (median 15 months). RESULTS: The 12 week PSA normalization rate was 79.4% for MAB and 38.6% for LHRH agonist monotherapy (P < 0.001). The 12 week overall tumor response rate was 77.5 and 65.3%, respectively (P = 0.063). The withdrawal rate due to ADRs was 8.8% and 10.9%, respectively. There were differences in favor of MAB over monotherapy with respect to time to treatment failure (TTTF) (P = 0.038) and time to progression (TTP) (P = 0.016). There have been too few deaths (n = 10) to analyze survival. The profiles of adverse events and ADRs were broadly similar in the two treatment groups. CONCLUSION: In Japanese patients with advanced prostate cancer, first-line treatment with bicalutamide 80 mg in combination with an LHRH agonist is superior to LHRH agonist monotherapy in terms of the antitumor response at 12 weeks, and also time to treatment failure and progression, and does not compromise treatment safety. The study is ongoing.