Background: In 1976, we initiated a randomized trial to determine whether lumpectomy with or without radiation therapy was as effective as total mastectomy for the treatment of invasive breast cancer.

Methods: A total of 1851 women for whom follow-up data were available and nodal status was known underwent randomly assigned treatment consisting of total mastectomy, lumpectomy alone, or lumpectomy and breast irradiation. Kaplan-Meier and cumulative-incidence estimates of the outcome were obtained.

Results: The cumulative incidence of recurrent tumor in the ipsilateral breast was 14.3 percent in the women who underwent lumpectomy and breast irradiation, as compared with 39.2 percent in the women who underwent lumpectomy without irradiation (P<0.001). No significant differences were observed among the three groups of women with respect to disease-free survival, distant-disease-free survival, or overall survival. The hazard ratio for death among the women who underwent lumpectomy alone, as compared with those who underwent total mastectomy, was 1.05 (95 percent confidence interval, 0.90 to 1.23; P=0.51). The hazard ratio for death among the women who underwent lumpectomy followed by breast irradiation, as compared with those who underwent total mastectomy, was 0.97 (95 percent confidence interval, 0.83 to 1.14; P=0.74). Among the lumpectomy-treated women whose surgical specimens had tumor-free margins, the hazard ratio for death among the women who underwent postoperative breast irradiation, as compared with those who did not, was 0.91 (95 percent confidence interval, 0.77 to 1.06; P=0.23). Radiation therapy was associated with a marginally significant decrease in deaths due to breast cancer. This decrease was partially offset by an increase in deaths from other causes.

Conclusions: Lumpectomy followed by breast irradiation continues to be appropriate therapy for women with breast cancer, provided that the margins of resected specimens are free of tumor and an acceptable cosmetic result can be obtained.