Adjuvant chemotherapy for gastric cancer in Japan: global and Japanese perspectives

Adjuvant therapy for gastric cancer after surgical resection has been under clinical investigation for decades. However, up until now, consistent and concrete evidence has not been generated either in Japan or other countries in favor of adjuvant therapy in terms of survival compared to surgery alone. Meta-analyses reported from Western countries have shown either no or borderline benefit for chemotherapy after surgical resection of gastric cancer. A recent trial showed significant benefit for chemoradiotherapy. However, Japanese specialists believe that their perspectives are different from those in the West due to the following: (1) gastric cancer incidence is several times higher in Japan; (2) more stringent screening programs are emphasized in Japan, thus baseline conditions of cancer patients are different; (3) specific operative techniques are used; and (4) Japanese surgeons have probably acquired additional experience in gastric cancer resection techniques. From the 1960s to the 1980s first mitomycin (MMC) and, later, a combination of oral fluorinated pyrimidines (o-FP) and MMC showed improved survival benefit in Japan compared to surgery alone. However, in the late 1980s, an expert group re-examined the results of previous trials, questioned them, and suggested fresh trials. Since then, the Japanese Clinical Oncology Group (JCOG) has conducted relevant trials to re-examine the effect of MMC and/or o-FP as adjuvant chemotherapy. The results of trials JCOG 8801 and JCOG 9206 have already been reported, and the accrual of patients for another trial (NSAS-GC trial) has just been completed. A pooled analysis of the two preceding trials showed a borderline survival benefit for o-FP compared to surgery alone. If o-FP treatment shows a 5% difference in survival benefit in the NSAS-GC trial, a meta-analysis of the three trials would probably reveal overall significant results. In conclusion, this therapy could become the standard adjuvant treatment regimen for gastric cancer patients after curative resection in Japan.