Appropriate Number of Adjuvant Chemotherapy Cycles for Patients with Stage 2 or 3 Gastric Cancer After Curative Gastrectomy: A Multicenter Cohort Study

Background: Few studies have presented evidence pertaining to the adequate minimum number of adjuvant chemotherapy (AC) cycles required to achieve an oncologic benefit for gastric cancer. Methods: From January 2012 to December 2013, data from patients who underwent curative radical gastrectomy and consequently received AC for pathologic stage 2 or 3 gastric cancer at 27 institutions in South Korea were analyzed. Results: The study enrolled 925 patients, 661 patients (71.5%) who completed 8 cycles of AC and 264 patients (28.5%) who did not. Compared with the mean disease-free survival (DFS) of the patients who completed 8 AC cycles (69.3 months), the mean DFS of patients who completed 6 AC cycles (72.4 months; p = 0.531) and those who completed 7 AC cycles (63.7 months; p = 0.184) did not differ significantly. However, the mean DFS of the patients who completed 5 AC cycles (48.2 months; p = 0.016) and those who completed 1–4 AC cycles (62.9 months; p = 0.036) was significantly lower than the DFS of those who completed 8 AC cycles. In the multivariate Cox proportional hazards analysis, the mean DFS was significantly affected by advanced stage, large tumor size, positive vascular invasion, and number of completed AC cycles (1–5 cycles: hazard ratio 1.45; 95% confidence interval 1.01–2.08; p = 0.041). Conclusion: The current multicenter observational cohort study showed that the mean DFS for 6 or 7 AC cycles was similar to that for 8 AC cycles as an adjuvant treatment for gastric cancer.