胃癌化学療法の考え方―欧米とわが国の比較

Current Strategy of Chemotherapy for Advanced Gastric Cancer : The Differences between Western Countries and Japan

要旨　20世紀に行われた無作為化比較試験において，奏効率および無増悪生存期間で5-FU単剤を上回る成績を示した多剤併用療法はいくつも存在する．しかし全生存期間において5-FU単剤を凌駕した多剤併用療法はいまだ出現していない．この事実は，胃癌化学療法の考え方を語るうえで無視できない事実である．しかし欧米では，5-FU単剤を無視した多剤併用療法同士の無作為化比較試験が繰り返し行われている．一方わが国においては，日本臨床腫瘍研究グループ（JCOG）が5-FU単剤をreference armとした無作為化比較試験を展開している．特に現在行われているJCOG9912は，5-FU単剤と欧米で好んで使われているCPT-11＋CDDPを比較する試験である．近い将来その結果が明らかにされたときに，欧米とわが国の胃癌化学療法に対する考え方に接点が生まれ，それが礎となって胃癌化学療法の新たな展開が始まるものと思われる．

　Many combination regimens based on 5-FU have been studied clinically to further improve the objective response rate and the overall survival for unresectable advanced gastric cancer. The additive survival advantage yielded by these combination therapies appears to be marginal, however, so no standard regimen has yet been established. The Japan Clinical Oncology Group (JCOG) conducted a randomized phase III trial that compared 5-FU alone with 5-FU＋cisplatin (JCOG 9205). Both regimens showed an equivalence not only in median survival time but also in one- and two-year survival rates. The toxicities were significantly lower with 5-FU alone than with 5-FU＋cisplatin. For this reason, the JCOG steering committee determined that 5-FU alone should be the reference arm in the next study. But there were no randomized trials using 5-FU alone as a reference arm excluding NCCTG trials in western countries. JCOG is now conducting a 3-arm randomized controlled trial comparing 5-FU alone with CPT-11＋CDDP and with S-1 alone (JCOG 9912). This study compares a single agent, 5-FU alone, with a toxic new combination, CPT-11＋CDDP, which is a very popular regimen in Western countries. The result of JCOG 9912 is very important for an understanding of the best treatment strategy for gastric cancer. This will give us the chance to share the same treatment strategy for future trials with Western investigators in the near future.