3536 Background: Neoadjuvant chemo-radiotherapy (CRT) is the standard of care for patients (pts) with u>T3 by endoscopic ultrasound (EUS) rectal cancer. Although pts with complete pathological response (ypT0N0) fare well in multiple series, there is uncertainty of whether it’s due to the induction (CRT), due to the adjuvant chemotherapy (ACT) or due to the combination of both therapies. We have evaluated long-term outcomes in CRT-treated pts. Those with ypT0N0, were not treated with ACT. Methods: Pts with u>T3 rectal cancer, received neoadjuvant chemotherapy (225mg/m2/day 5-fluorouracil (FU)) in continuous infusion (CI) per 5 weeks (wks) and concomitant radiotherapy (45 Gy). Laparoscopic surgery (LAP) was planned after an interval of 5-8 wks. Pts achieving ypT0N0 were no treated with ACT. Pts with ypT>1 or N1 were treated with 3 gr/m2 FU in 48 hour CI and LV 200 mg/m2 every 2 wks x 6 cycles. Results: From November 2000 to November 2008, a cohort of 173 pts were treated with induction CRT and 167 pts underwent total mesorectal excision (LAP, n=158, open surgery n=9). Complete pathological response was achieved in 26/167 pts (15.5%). After a median follow-up of 58.3 months, pts with ypT0N0 have a 5-year disease-free survival and overall survival rate of 96% (95% CI 76 to 99%) and 100% (95% CI not estimable) respectively. Conclusions: Using these results, a clinical trial comparing observation versus adjuvant therapy in ypT0N0 after standard CRT, would need to enroll 3088 pts to show a HR of 0.75 in favor of ACT after 5 years of follow-up (alpha=.05, beta=.2). In case that the true DFS lied in the lower bound of the 95% CI, 636 patients would be needed under the same assumptions. These results do not support the administration of ACT to ypT0N0 patients.
Outcome of patients with pancreatic adenocarcinoma with complete pathological response following neo-adjuvant therapy
