SAN ANTONIO—In the treatment of early-stage breast cancer, postoperative radiation therapy after sector resection (breast-conserving surgery) reduces recurrences but does not influence survival, according to a Swedish study presented at the 23rd Annual San Antonio Breast Cancer Symposium.
Investigators from the Swedish Breast Cancer Group, Lund, Sweden, presented findings based on 1,188 women with stage I and II node-negative breast cancer treated between 1991 and 1997 with radical resection.
Patients were randomized to postoperative radiotherapy, 50 Gy in 25 fractions over 5 weeks (n = 593), or no postoperative irradiation (n = 595). Median age was 60 and median tumor size was 12 mm; 65% of cases were detected by mammographic screening.
Per Olof Malmstrom, MD, PhD, of Lund University Hospital, reported no significant difference in survival according to whether or not patients received radiotherapy in addition to surgery. Overall survival at 5 years was 94% among patients receiving radiotherapy and 93% in the control group (follow-up of patients alive was 6.5 years). Deaths from breast cancer occurred in 4% of the control patients and 3% of radiotherapy-treated patients.
Event-free survival at 5 years, however, was more favorable in the radiotherapy group: 85% vs 75% in the control group (P = .001). Ipsilateral breast recurrence as a first event occurred in 14% of controls (78 patients) and 4% of radiotherapy patients (26 patients), for a statistically significant threefold difference (P < .0001).
Other first events that were not significant included the following for the control group and radiotherapy group, respectively: axillary recurrence in 6 and 3; distant metastases, 25 and 23; contralateral breast cancer, 17 and 17; and non-breast-cancer deaths, 18 and 20.
Regarding recurrence, the best prognostic factors were age 50 and older in the irradiated group (P = .07) and age 50 and older plus detection by mammographic screening in the nonirradiated group (P = .001).
"Radiotherapy after resection decreases ipsilateral breast recurrences rates, but there is no influence on breast cancer mortality or overall survival. In patients not getting radiotherapy, there is a lower risk of recurrence among patients over age 50 whose tumors are detected by screening," he concluded.
