Survival Impact of Adjuvant Chemotherapy for Resected Locally Advanced Rectal Adenocarcinoma

Recent data has created uncertainty regarding the benefit of adjuvant fluoropyrimidine-containing chemotherapy following preoperative chemoradiotherapy and surgical resection for locally advanced rectal cancer (LARC). In particular, patients with a pathologic complete response (pCR) may derive no benefit from adjuvant chemotherapy.

This is a retrospective analysis of patients with LARC, diagnosed between January 1, 2003 and December 31, 2014 at 3 Melbourne health services. Patients were identified from the Australian Comprehensive Cancer Outcomes and Research Database, where a defined data set is prospectively collected on consecutive patients. Patient demographics, pCR rates, postoperative treatment, recurrence, and survival were analyzed.

A total of 717 patients with LARC were identified, of whom 555 (77%) had received preoperative long-course chemoradiation followed by surgery. Four hundred fifty-two of 555 patients (81%) subsequently received adjuvant fluoropyrimidine-based chemotherapy. At a median follow-up of 45.9 months, 95 (21%) patients in the adjuvant chemotherapy group and 20 (19%) in the surveillance group had relapsed. Five-year relapse-free survival was 77% in the adjuvant chemotherapy group and 71% in the surveillance group with no significant difference on univariate analysis (hazard ratio [HR], 0.93; 95% confidence interval [CI], 0.58-1.51; P = .780). No significant impact on relapse-free survival was seen for either pCR or non-pCR patients. Five-year overall survival (OS) was 85% in the adjuvant chemotherapy group and 74% in the surveillance group with a nonsignificant trend towards OS benefit (HR, 0.62; 95% CI, 0.37-1.05; P = .074). A significant OS benefit favoring adjuvant chemotherapy was seen in the non-pCR subset of patients (HR, 0.49; 95% CI, 0.28-0.86; P = .014).

A high proportion of patients in this routine practice cohort received adjuvant chemotherapy following preoperative treatment and surgery for LARC. Adjuvant chemotherapy administration was associated with a significant improvement in 5-year OS only in the patients with a non-pCR.