[Histological and biological evaluation of preoperative radiotherapy on T1N0 breast carcinoma].

In order to clarify the role of radiotherapy in breast preserving surgery for early breast cancer, histological and biological effects of preoperative radiation were evaluated. Thirty-five T1N0 patients were treated by preoperative radiotherapy with beta-tron, cumulative doses of which were ranging from 25 Gy (5 Gy x 5) to 40 Gy (8 Gy x 5) and underwent subsequent modified radical mastectomy 2 or 3 weeks after the termination of radiotherapy. Clinical tumor shrinkage more than 50% was observed in 25 out of 35 cases (71%) but did not directly correlate with histological effects. Radiotherapy was basically ineffective within 25-30 Gy, whereas histological effects more than Grade 2 were gained in 8 out of 25 patients (32%), who had received 40 Gy or more. In the preoperative radiation group, there were more ER(+), PgR(+) and histologically well-differentiated cases than in the non-radiated stage I patients. Mitotic figures were also significantly reduced after radiotherapy, whereas the expression of c-erB-2 protein was unchanged between these two groups. Our data indicate the various radiosensitivity of breast cancer cells and the indication of hormone therapy for the conservative treatment of breast carcinoma.