Purpose: In 1984, the German Breast Cancer Study Group (GBSG) started a multicenter randomized clinical trial to compare the effectiveness of three versus six cycles of 500 mg/m2 cyclophosphamide, 40 mg/m2 methotrexate, and 600 mg/m2 fluorouracil (CMF) on day 1 and 8 starting perioperatively with or without tamoxifen (TAM) (3 x 10 mg/d for 2 years). The aim of the trial was to compare recurrence-free and overall survival between the different treatment modalities.
Patients and methods: During 5 years, 41 institutions randomized 473 patients (3 x CMF: 145; 3 x CMF + TAM: 93; 6 x CMF 144; 6 x CMF + TAM: 91). Until March 31, 1992, median follow-up time was 56 months with 197 events for disease-free survival and 116 deaths observed. This provides a power of approximately 80% to detect a potential treatment difference corresponding to a relative risk (RR) of 0.67 for recurrence-free survival. Treatment modalities and various patient characteristics were evaluated by means of a multivariate Cox regression analysis.
Results: No significant difference in recurrence-free survival was observed with respect to hormonal therapy (RR = 0.75 TAM v no TAM; 95% confidence interval [CI], 0.54 to 1.04; P = .08) as well as duration of chemotherapy (RR = 0.90 of 6 x CMF v 3 x CMF; 95% CI, 0.67 to 1.19; P = .45). Similar results were obtained for overall survival. The multivariate analysis revealed a significant prognostic impact of the number of positive lymph nodes and the progesterone receptor level on recurrence-free survival. Compliance with chemotherapy within the range of 85% to 115% of the target dose was achieved in 94% and 78% of the patients randomized to 3 x CMF and 6 x CMF, respectively. Sufficient compliance with TAM was reported for 141 patients (93%).
Conclusion: At this stage of follow-up, six courses of CMF are not superior to three courses with respect to recurrence-free survival.