Adjuvant therapy of gastric cancer: the Japanese experience

The 5-year survival rate of patients with advanced gastric cancer who undergo curative resection is gradually increasing and currently ranges between 67.1% to 76.4% at the five major cancer centers in Japan. A belief that minimal residual disease has a high probability of being cured with adjuvant therapy prompted Japanese investigators to develop the D2 dissection with extended lymphadenectomy, more detailed pathologic staging, perioperative chemotherapy, and chemoimmunotherapy. This review focuses on comparative trials performed in Japan studying the use of adjuvant therapy with either chemotherapy alone or chemotherapy plus immunotherapy in the treatment of patients with curatively resected gastric carcinoma. Preoperative and intraperitoneal therapy also has been evaluated. At present, however, no chemotherapy has been shown to impact favorably on the survival of gastric cancer patients, whereas the biological response modifiers, PSK or OK-432, seem to add some benefit to chemotherapy in the adjuvant setting. Carefully designed randomized controlled trials with sufficient size which include a surgery-alone control arm are the only way to establish the efficacy of adjuvant therapy.