Adjuvant treatment for resected rectal cancer: Effect of postoperative oxaliplatin added to 5-FU in the neoadjuvant era.
672 Background: Oxaliplatin (Ox) added to postoperative 5-fluorouracil (5FU) based adjuvant treatment has shown a survival benefit in colon cancer. For rectal cancer, the impact of Ox on survival has almost exclusively been tested in studies using 5FU +/- Ox both as a component of preoperative chemoradiotherapy (CRT) and as adjuvant treatment. Only one study (NCT00807911) investigated adjuvant 5FU +/- Ox in patients undergoing preop 5FU based CRT without Ox. Thus, the evidence for the benefit of adding Ox to adjuvant 5FU in patients treated with preop 5FU based CRT is limited. Methods: Data from the prospective German multicenter Quality Assurance in Rectal Cancer observational trial involving more than 300 hospitals of all levels of care throughout Germany were retrospectively analyzed. Patients undergoing R0 total mesorectal excision (TME) for rectal cancer following neoadjuvant 5FU based treatment without oxaliplatin between 01/01/2008 and 12/31/2010 were included. Disease-free survival (DFS) in patients receiving adjuvant treatment with or without Ox was compared using the Kaplan Meier method. The impact of adjuvant treatment with 5FU with or without Ox on DFS was investigated in a Cox regression analysis including open vs. laparoscopic approach, pT stage, pN stage, tumor grading, TME quality grade, and presence of anastomotic leakage as potential confounding factors. Results: The entire data set included 1,861 patients. Data for all variables investigated were available for 599 patients of whom 512 (85%) and 89 (15%) received 5FU based adjuvant treatment without and with Ox, respectively. Mean DFS was not different in patients receiving 5FU only vs. 5FU with Ox (p=0.103). Cox regression analysis revealed no significant impact of adding Ox to adjuvant 5FU on DFS. Of all factors analyzed, only pN2 (vs. pN0) status had an independent adverse effect on DFS (Hazard ratio 4.22, p<0.001). Conclusions: These data indicate that adjuvant Ox added to 5FU does not provide a DFS benefit in rectal cancer patients treated with preoperative 5FU based CRT under routine care conditions. Rectal cancer patients may be different from patients with colon cancer with respect to benefit from adjuvant Ox.