BACKGROUND A phase III randomized trial was activated to evaluate the efficacy of preoperative combined chemotherapy and radiotherapy as compared to preoperative radiation therapy alone, in patients with breast cancer presenting with a clinical stage of IIb-IIIa (TNM classification). METHODS From 1985 to 1990, 271 patients, aged 27-55 years, with stage IIb-IIIa breast cancer were randomized to receive either one or two courses of thiotepa 20 mg (i.m. injection) on the days 1, 3, 5, 7, 9, 11 (total dose per course 120 mg), methotrexate 40 mg/m2, i.v. on days 1 and 8, and 5-fluorouracil 500 mg/m2, i.v. on days 1 and 8 (TMF regimen) plus radiotherapy (Group I, 137 patients), or preoperative radiation therapy only (Group II, 134 patients). After the preoperative treatment all patients underwent mastectomy and complete axillary clearance, and then received 4-6 courses of TMF. The trial was conducted in a single institution (N.N. Petrov Research Institute of Oncology, St. Petersburg). RESULTS Histopathological assessment of the mastectomy specimens showed complete regression of the tumour in 29.1% of the patients in group I and in 19.4% of the patients e.c. in group II. The estimated 5-year overall survival percentages were 86.1% for group I, and 78.3% for group II (P > 0.05). 5-year disease-free survival percentages were 81.0% and 71.6%, respectively (p < 0.05). CONCLUSIONS Despite the low number of the patients included in the trial, we were able to detect a significant improvement in treatment results with a combination of chemotherapy and radiation therapy given prior to mastectomy over those of local therapy alone with radiation therapy followed by mastectomy, for average- and high-risk patients with operable breast cancer.