Exploratory analysis of adjuvant chemotherapy benefits after preoperative chemoradiotherapy and radical resection for rectal cancer.

Abstract

3556 Background: Evidence regarding adjuvant chemotherapy (CTx) for patients with rectal cancer after preoperative chemoradiotherapy (CXRT) is limited. The aim of study was to explore the relationship between CXRT response and adjuvant CTx for patients with rectal cancer treated by CXRT and radical resection. Methods: We performed a retrospective consecutive cohort study of patients with locally advanced (cStage II-III by EUS, CT, or MRI) rectal carcinoma treated with preoperative CXRT and radical resection, 1993 to 2008. To explore the late effects, we performed a landmark analysis of patients alive without recurrence at 24 months. The duration free from recurrence (FFR) was compared among patients with complete (CR, ypT0N0), intermediate (IR, ypT1-2N0), or poor (PR, ypT3-4 or N+) response according to adjuvant CTx use and type using multivariate Cox regression. Results: A total of 725 patients met criteria and were evaluated. Median follow-up was 69 months (IQR: 39-104 months). 611 patients received adjuvant CTx: 447 with fluoropyrimidine only (FP), and 139 also received oxaliplatin (Ox). Although receipt of adjuvant chemotherapy was not associated with 5-year FFR overall, (HR: 0.91, 95% CI: 0.58-1.43), adjuvant therapy did appear to suggest a benefit in the IR group (HR, 0.49; 95%CI, 0.21-1.19). 2-year landmark analysis showed that adjuvant CTx was associated with a significant improvement in FFR among the IR patients only (HR, 0.28; 95% CI, 0.08-1.00, p=0.04). Among PR patients FP alone did not improve FFR (HR, 1.22; 95% CI, 0.7-2.12) but the addition of Ox was associated with a non-significant reversal in the direction of the effect (HR, 0.53; 95% CI, 0.16-1.79). Conclusions: In this exploratory analysis, the addition of adjuvant FP CTx appeared to favorably affect the duration FFR only for patients with rectal cancer and intermediate response to CXRT followed by radical resection. These data support the investigation of the role for adjuvant fluoropyrimidine therapy among patients with CR or IR and the addition of oxaliplatin for PR patients.