Long-term survival benefits of adjuvant chemotherapy by decreasing incidence of tumor recurrence without delaying relapse in stage III colorectal cancer

Backgrounds and aims To elucidate the survival benefits of adjuvant chemotherapy by decreasing incidence or by delaying time of tumor recurrence, we reported the longterm results of a nonrandomized prospective study comparing the adjuvant chemotherapy to no chemotherapy in stage III colorectal cancer. Patients From 1991 to 1995, 463 patients with stage III colorectal cancer were divided to three groups which were no chemotherapy, weekly chemotherapy, and monthly chemotherapy (5-FU plus levamisole). Results The recurrent incidence was significantly decreased in patients with chemotherapy (47.8% vs. 63.9% of no chemotherapy, P=0.001), resulting into better survival. The 10-year cancer-specific and overall survival rates of patients with chemotherapy vs. no chemotherapy were 52.1% vs. 37.8% and 46.9% vs. 29.9%, respectively (P<0.001). Weekly chemotherapy had better survival than monthly chemotherapy (P<0.05). There was no significant difference in recurrent time or types between the patients with and without chemotherapy. The percentages of patients with recurrence happened within 3 years were 85.2% and 84.6% of those with and without chemotherapy, respectively. Patients with advanced stage of T4b invasion depth, N2, and central node invasion had no significant survival benefits by adjuvant chemotherapy. Conclusions Long-term survival benefits achieved by adjuvant chemotherapy is through decreasing recurrent incidence, not through postponing tumor recurrent time. That means adjuvant chemotherapy indeed cures some patients by eradicating occult tumor. In adjuvant setting, more powerful regimen for eradicating occult tumor is the keystone to improve long-term survival of stage III colorectal cancer.