Association of time to adjuvant chemotherapy (TTAC) and overall survival among patients with rectal cancer treated with preoperative radiation.

Abstract

461 Background: Studies suggest that delayed adjuvant chemotherapy (AC) beyond 8 weeks is associated with inferior survival in early-stage colon cancer (CA). The optimal TTAC in rectal CA remains unclear. The objective of this study was to determine the prognostic effect of TTAC in stage II and III rectal CA treated with standard preoperative (op) chemoradiation. Methods: Patients with stage II/III rectal CA treated with pre-op chemoradiation, received post-op AC, and referred to the British Columbia Cancer Agency between 1999 and 2008 were included. Univariate and multivariate analyses were conducted using Kaplan Meier and Cox regression methods to evaluate the association between TTAC and outcomes. X-tiles cut-point analysis was performed to determine the optimal TTAC. Results: A total of 327 eligible patients were identified: median age 61 (range 22-85), 70% male, and 75% stage III. In terms post-op AC, 51% received 5-fluorouracil (5-FU), 32% received capecitabine, 12% received 5-FU and oxaliplatin, and 5% received other chemotherapy. Median TTAC was 7.0 weeks (wks) (range 1.6-33.3 wks). Cut-point analysis revealed the optimal TTAC to be 5.6 wks (HR: 0.42, 95%CI 0.22-0.82, p=0.0087). Initiation of AC within optimal TTAC (5.6 wks) and 6 wks from date of surgery (sx) was associated with a significant survival benefit while no significant effect was seen at 8 wks. TTAC of ≤ 6 wkswas found to be a significant prognostic factor in multivariate analysis (p=0.047) adjusted for ECOG, age, sex, stage, margin status, and grade. In stratified analysis by stage, patients with stage III disease benefited from AC (p=0.018) while those with stage II did not (p=0.71). Conclusions: In this study, the optimal TTAC was 6 weeks or less. Initiation of AC within this time frame was associated with improved OS. This is less than the optimal timeframe indicated in the literature for colon CA. [Table: see text]