e15101 Background: Between April 2006 and May 2008, 27 rectal adenocarcinoma pt were included (cT3: 25 pt, T4: 2 pt, N0: 11 Pt, N+: 16 pt), stages II-III, RMN staged, 14 male and 13 female. Mehtod: Neoadjuvant treatment was: Ox: 50 mg/m2 weekly, oral Cp: 825 mg/m2 tid the days of the Rt, and a Rt of 50.4 Gy. 9 pt had a lower third tumor, 9 middle, 9 upper. Surgery was planned 6–8 weeks after treatment´s end. 4 adjuvant chemotherapy cycles with Xelox were planned. Results: 7 pt had pCR (26%), 2 pt progression disease 18 pt tumor downstaging(dwst). Percentages of dwst were: T 85%, N 37%. Sphincter preservation (sp) was 81.9%, for tumors of the lower third sp was 44.4%. Presurgical (prsrg) RMN did not predict the pathological result in 21 pt. Main side effects: Dermatitis G1 in 21 pt, and G2 in 4 pt. Diarrhea 12 pt G1, 11 pt G2, and 4 pt G3. Hand and foot G1 5 Pt and G2 4 pt. Paresthesias G1 10 pt, G2 7 pt. Leucopenia 6 pt G1. 4 Pt did not complete treatment because of toxicity. Median Rt dose was 49.7 Gy (47.5–50.4 Gy).At a mean follow up of 22.5 months (7–31) 4 pt presented metastatic disease (15% ), none in the pCR group. Mean pre-neoadjuvant (preneo) CEA was 6.8 ng/ml (2.1–17.0). There was difference statistically significant when compared preneo CEA vs prsrg CEA: 2.72 ng/ml inferior with the second outcome (p<0.001). Mean prsurg CEA was 4.1 (0.1–12.0). In the subgroup with pCR the mean prsrg CEA was 1.1 (0.5–1.5), and in non-pCR it was 5.1 (0.1–12.0). Comparing the prsrg CEA between pCR and the non-pCR subgroups, the mean difference was 4.0 ng/ml greater in the non pCR. This difference was statistically significant (p=0.002, 95% CI: 1.68–6.3).We found a nadir of <5ng/ml as significantly associated with pCR (p=0.036). Conclusions: Preoperative chemoradiotherapy with Ox and Cp, is safe and well tolerated. Offers an interesting ratio of pCR, and of tumor downstaging. Prsrg CEA level and CEA nadir should be studied as predictors of pCR. It is possible that with more patients, the significant nadir level could be lower. We consider this combination and the CEA nadir interesting to be included in further studies. No significant financial relationships to disclose.