Effect of time interval between surgery and preoperative chemoradiotherapy with 5-fluorouracil or 5-fluorouracil and oxaliplatin on outcomes in rectal cancer

Background and Objectives: Preoperative chemoradiotherapy for locally advanced rectal cancer is now considered "standard of care." However, the optimal time interval for resection after neoadjuvant therapy is unknown. Methods: Between 11/90 and 11/04, 107 patients with rectal adenocarcinoma underwent preoperative chemo/RT at the University of Pennsylvania. Fifty-six percent had LAR and 40% had APR. Chemotherapy consisted of 5-FU/oxaliplatin in 28% and 5-FU in 72% of patients. All patients received preoperative RT. Results: A longer time interval between chemo/RT and surgery was associated with tumor downstaging (OR 1.24, P = 0.02). A longer time interval was not associated with: nodal downstaging (OR 1.00, P = 0.98); pathologic complete response (PCR) (OR 0.97, P = 0.80); likelihood of performing an LAR (OR 0.90, P = 0.47); improved disease free survival (DFS), local control, or distant control (HR 1.05, P = 0.49; HR 1.14, P=0.22; HR 1.06, P=0.52, respectively). The PCR rate was 34.5% in the 5-FU/oxaliplatin/radiation group, and 13.7% in the 5-FU/radiation group. If patients with microscopic CR were excluded, then the PCR rate for 5FU/OX was 21.4% and for 5-FU was 12.2%. Conclusions: Time interval between surgery and chemo/RT appeared to have little effect on PCR or LAR rates. Patients receiving 5 FU/oxaliplatin/RT had a high PCR rate. A prospective randomized trial to test superiority of 5 FU/oxaliplatin is warranted.