Postoperative local radiotherapy in rectal cancer: treatment results with limited radiation fields

The purpose of this study is to determine the treatment results and complication rates of postoperative local radiotherapy, with doses per fraction of 2.25 to 2.50 Gy, in patients with rectal carcinoma who have received macroscopically radical surgery.

A retrospective analysis was done of the records of all consecutive patients (N = 147) with rectal carcinoma Dukes' Stage B or C who have received postoperative local radiotherapy in our institution in the years 1981 through 1989. All patients have been treated on a limited target area covered by only local radiation fields. Locoregional fields covering the whole iliac node chains have not been given. In our treatment protocol doses per fraction were from 2.25 to 2.50 Gy and total doses from 50 to 55 Gy. The minimum follow-up was 24 months; eight patients have been lost to follow-up.

The overall 5-year survival rate for the whole group of patients was 39%. The actuarial 2- and 5-year pelvic recurrence rates were 14% and 22% respectively for Dukes' B patients and 30% and 38% respectively for Dukes' C patients. The difference between the pelvic recurrence rates of Stage B and Stage C patients was statistically significant (p = 0.009). No other factors with prognostic significance for pelvic recurrence were found. The interval between surgery and radiotherapy especially had no influence on pelvic recurrence rates. The 35 pelvic recurrences were classified as follows: 17 in-field, 5 marginal, 1 out-of-field, and 9 peritoneal seeding; in three patients there was not enough information for classification. Of the 32 classified pelvic recurrences, the five marginal recurrences were probably geographical misses, only the one out-of-field recurrences, the five marginal recurrences were probably geographical misses; only the one out-of-field recurrence might have been prevented with locoregional radiotherapy. Serious complications caused by the radiotherapy have occurred in 3% of the patients.

We conclude that the results of postoperative local radiotherapy alone are comparable with the published results of locoregional radiation. Even when relatively high doses per fraction are given low complication rates are seen.