[en] Objective: Since 1979, our institution has treated locally advanced rectal cancer with preoperative irradiation followed by resection with or without intraoperative radiation therapy (IORT). In 1986, our preoperative treatment policy was changed to include bolus 5-FU chemotherapy concurrent with irradiation in hopes of improving resectability, downstaging and/or local control rates. We report the long-term results with the addition of 5-FU chemotherapy to preoperative irradiation. Materials and Methods: From 1979 - 1994, 200 patients with locally advanced rectal carcinoma (primary or recurrent) received preoperative irradiation, resection and IORT if indicated. Bolus 5-FU (500mg/m²/day) chemotherapy was administered for three days during weeks one and five of irradiation. The change in treatment policy was limited to the addition of 5-FU chemotherapy: the radiation techniques (four-field), doses (50.4 Gy), and indications for intraoperative radiation (microscopic residual, gross residual, tumor adherence) remained constant. The median follow-up for the entire group of patients was 33 months (.95 months - 199 months), and the minimum follow-up was 1.5 years. Tabular results are 5-year actuarial calculations. Results: One hundred and five patients received preoperative 5-FU chemotherapy and irradiation whereas 95 patients underwent preoperative irradiation alone. Sixty-five percent of the patients were able to undergo complete resections, and 53% had transmural disease upon pathologic examination. The addition of chemotherapy did not affect the rates of resectability or tumor downstaging. However, the 10-year local control rate was significantly improved for those patients who received preoperative chemotherapy: 77% vs. 44% (p<0.01) (see figure). When stratified by extent of resection and stage, those patients who underwent complete resections or had transmural disease had significantly improved local control rates when compared to the non-chemotherapy group: No difference in survival was seen based on the administration of chemotherapy. Conclusions: With long-term follow-up, the addition of 5-FU chemotherapy provides a significant local control benefit for patients presenting with locally advanced rectal carcinoma. The benefit was limited to those patients with complete resections and transmural disease. This finding supports escalating the role of 5-FU chemotherapy: firstly, with continuous infusion concurrent with irradiation; and secondly, with maintenance therapy postoperatively