目的：研究術前放射治療應用於低位直腸癌患者，在促進器官保留之角色，並評估其治療結果及後遺症。 材料和方法：從 1992 年 4 月至 1996 年 12 月，共有 43 位直腸癌患者因腫瘤位置過於接近肛門，經外科醫師判斷無法同時切除腫瘤並保留肛門，為了提高病患接受腫瘤切除並保留肛門之機會，於本科接受術前放射治療。照射範圍為骨盆腔，劑量為 37.5Gy，計 15 次，每週治療五天。結果：放射治療後有 30 位 (70%) 患者可接受保存肛門之低前位切除術。三年整體存活率、無病存活率、局部控制率各為 60%、62% 及 89%。單變數分析發現病理分期及局部淋巴結轉移對於整體存活率及無病存活率為有意義之預後因子。對於局部控制率則只有局部淋巴結轉移為有意義之預後因子。接受保存肛門之低前位切除術並不影響患者之存活率及局部控制率。以多變數分析發現病理分期為影響無病存活率之獨立因子，而局部淋巴結轉移為影響局部控制率之獨立因子。結論：術前放射治療應用於低位直腸癌患者，可使病患有相當機會接受保留肛門之切除術。同時，經由術前放射治療而保存之肛門，其括約肌功能在大部份病人皆為正常。如何改進治療技術，以減少放射治療之副作用，仍有待努力。

　　　　　Purpose:To study the impact of preoperative irradiation on enhancingsphincter preservation and to evaluate the treatment outcome in patients withlower rectal cancer. The results were analyzed for the endpoints of sphincterpreservation, sphincter function, pelvic control, disease-free survival, overallsurvival and treatment-related morbidities. Materials and Methods:From 1992 to1996, 43 patients with clinically resectable rectal cancer received preoperativeradiotherapy at our department. All of these patients had undergone aprospective clinical assessment by their surgeons and were declared to requirean abdominoperineal resection due to the proximity of the tumor to the analsphincter. The whole pelvis received 37.5 Gy in daily fraction of 2.5 Gy withparallel opposed anterior-posterior portals. Results:Thirty of the forty-threepatients (70%) were able to undergo low anterior resection. The majority (88%)of patients had good sphincter function after sphincter-preserving surgery. Thepathologic stage was T2 in 11 patients and T3 in 32 patients. The 3- yearoverall survival rate, disease-free survival rate, and local control rate of the43 patients were 60%, 62% and 89%, respectively. In univariate analysis,pathologic stage and the presence of regional lymphadenopathy were noted assignificant prognostic factors for both overall survival and disease-freesurvival. With regard to local control, only the presence of regionallymphadenopathy showed prognostic significance for local control. No differencein survival rate and local control rate was observed between patients undergoinglow anterior resection and those undergoing abdominoperineal resection. Inmultivariate analysis, pathologic state was noted as the only independentprognostic factor for disease-free survival; likewise, only the presence oflymphadenopathy was demonstrated as an independent predictor for local control.No clinical and pathologic parameters were proved to be independent prognosticfactors for overall survival. Acute intestinal toxicity included grade 1 in 10(23%) patients, grade 2 in 18(42%) patients, and grade 3 in 2 patients (5%). Nopatients had acute urological toxicity. Conclusion:With the help of preoperativeradiotherapy, a significant proportion of patients would have a chance toreceive sphincter-preserving surgery. Furthermore, the preserved sphincterfunctioned well in most of the patients. Further efforts should be made toreduce the treatment-related morbidities.