Adjuvant Chemotherapy in Rectal Cancer Patients Treated With Preoperative Chemoradiation and Total Mesorectal Excision: A Multicenter and Retrospective Propensity-Score Matching Study

Purpose The role of adjuvant chemotherapy after preoperative chemoradiation therapy (CRT) and curative surgery in rectal cancer has yet to be definitely determined. We performed a retrospective and multicenter study to evaluate whether adjuvant chemotherapy (AC) could reduce recurrence and improve survival in locally advanced rectal cancer. Methods and Materials We analyzed data from 8 tertiary institutions for 1442 patients with rectal cancer who underwent preoperative CRT and total mesorectal excision. Patients were classified into 2 groups: the AC group (patients who received chemotherapy after surgery) and the observation group (those who did not receive chemotherapy after surgery). Propensity-score matching was used to assess the exact role of AC. The AC group was then subdivided to investigate the impact of adding oxaliplatin to 5-fluorouracil (5-FU). Group 1 was treated with 5-FU/folinic acid or capecitabine without oxaliplatin, and group 2 received 5-FU/folinic acid or capecitabine with oxaliplatin. Results The 3-year relapse-free survival rates in the AC and observation groups were 85.9% and 84.3%, respectively ( P  = .532). The 3-year overall survival rates in the AC and observation groups were 94.9% and 89.9%, respectively ( P  = .123). The rates of locoregional recurrence (2.2% vs 3.2%, P  = .294) and distant metastasis (12.4% vs 12.9%, P  = .927) at 3 years were not significantly different between the two groups. The 3-year relapse-free survival rates of group 1 and group 2 were 71.5% and 74.8%, respectively ( P  = .426). The 3-year overall survival rates of group 1 and group 2 were 89.9% and 96.5%, respectively ( P  = .102). Conclusions This multicenter study found insufficient evidence to support the use of 5-FU–based AC after preoperative CRT and curative surgery in rectal cancer.