Is it necessary to irradiate the breast after conservative surgery for localized cancer?

Two hundred one patients with operable breast cancer received postoperative irradiation after limited surgery and were followed up for five years. Fifty-three patients (26%) had positive margins. The breast cancer recurrence rate at five years was 14%, less than half the incidence reported for patients treated by limited surgery only. Those with positive margins who received irradiation had a recurrence rate of only 13%. Another 324 patients with tumors (less than or equal to 3 cm) N0 who were treated similarly were evaluated for distant dissemination in relation to local control. Patients who remained free of local disease or developed recurrences more than five years after treatment had significantly better distant disease-free and overall survival than patients who failed locally within five years. Breast irradiation after conservative surgery resulted in decrease in local recurrence and reduced the need for salvage mastectomy. Long-term follow-up of a large number of patients is necessary to determine the relation between local control and the decreased risk of distant dissemination.