Results of postoperative radiation therapy of rectal cancers: with the emphasis of the overall treatment time

To evaluate the results of the treatment of locally advanced but resectable rectal cancers and to analyze prognostic factors, especially with the emphasis on the treatment time factor. There were 71 patients with rectal cancer who had been treated by curative surgical procedure and postoperative radiotherapy from August 1989 to December 1993. The minimum follow up period was 24 months and the median follow-up was 35 months. Radiation therapy had been given by 6 MV linear accelerator by parallel opposing or four-box portals. Whole pelvis was treated up to 5040 cGy in most cases. Systemic chemotherapy had been given in 94% of the patients, mostly with 5-FU/ACNU regimen. Assessment for the overall and disease-free survival rates were done by life-table method and prognostic factors by Log-Rank tests. Five-year overall survival, disease-free survival were 58.8% and 57%, respectively. Two-year local control rate was 76.6%. Stage according to Modified Astler-Coller (MAC) system, over 4 positive lymph nodes, over 6 weeks interval between definitive surgery and adjuvant radiotherapy and over 7 days of interruption during radiotherapy period were statistically significant, or borderline significant prognostic factors. The treatment results of patients with rectal cancers are comparable to those of other large institutes. The treatment results for the patients with bowel wall penetration and/or positive regional lymph nodes were still discouraging for their high local recurrence rate for the patients with MAC 'C' stage diseases and high distant metastases rate even for the patients with node-negative diseases. Maybe more effective regimen of chemotherapy would be needed with proper route and schedule. To maximize postoperative adjuvant treatment, radiotherapy should be started at least within 6 weeks after surgery and preferably as soon as wound healing is completed. Interruption of treatment during radiotherapy course affects disease-free survival badly, especially if exceeds 7 days. So, the total treatment period from definitive surgery to the completion of radiotherapy should be kept as minimal as possible