A study on preoperative irradiation therapy in rectal cancer

The effects of preoperative radiotherapy in advanced rectal cancers were studied. Cases where the preoperative diagnoses of the depth of the lesion and positive regional nodal involvement were PM' or more and N1', respectively, were the indications for radiation. A dose of 30 Gy was administered using a Linac. Patients received surgery within two weeks after the start of radiotherapy. Grossly, the reduction rate in the major axis of the tumor and degress of stenosis and hemorrhage were all improved after a single dose of 30 Gy. When changes in the biopsy samples were evaluated by dose, early degenerative changes occurred in tumor cells at around 20 Gy, and interstitial changes as manifested by leukocyte reaction were noted at 20 - 40 Gy. According to ''the Oohoshi and Shimozato Classification,'' histologic changes in the major lesion were classified as IIb or more, the goal of our study, in 55.7 % of cases, suggesting that the effect is dose-dependent in mucinous carcinomas and squamous cell carcinomas. Factors ly and v which are the parameters for vascular invasion tended to decrease in the radiation group. From these, it was concluded that the dose required for preoperative radiotherapy is 30 - 40 Gy or more. The follow-up of the postoperative prognosis disclosed that the local recurrence rate was 9.1 % in the radiation group and 15.3 % in the non-radiation group, suggesting inhibition of local recurrence in the radiation group. The systemic recurrence rate was 40.9 % in the radiation group and 49.2 % in the non-radiation group, indicating improvement by 8.3 % in the former. Regarding the remote effect, the five-year survival rate was 53.2 % in the radiation group compared to 50.2 % in the non-radiation group, suggesting a significant difference (p < 0.05). (author)