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.