RANDOMIZED CLINICAL-TRIAL OF BREAST IRRADIATION FOLLOWING LUMPECTOMY AND AXILLARY DISSECTION FOR NODE-NEGATIVE BREAST-CANCER - AN UPDATE

Background: Breast-conservation surgery is now commonly used to treat breast cancer. Postoperative breast irradiation reduces cancer recurre nce in the breast. There is still controversy concerning the necessity of irradiation of the breast in all patients. Purpose: We present an update of results from a randomized clinical trial designed to examine the efficacy of breast irradiation following conservation surgery in the treatment of women with axillary lymph node-negative breast cancer . The patients were enrolled from April 1984 through February 1989. In itial results were published in 1992 after a median follow-up time of 43 months. It was reported that recurrence of cancer in the breast occ urred in 5.5% of the patients who received breast irradiation compared with 25.7% of those who did not. No difference in survival was detect ed between the two treatment groups. Now that the median patient follo w-up has reached 7.6 years, the trial end points have been re-examined and an attempt has again been made to identify a group of patients at low risk for recurrence of cancer in the breast. Methods: Eight hundr ed thirty-seven patients with node-negative breast cancer were randoml y assigned to receive either radiation therapy (n = 416) or no radiati on therapy (n = 421) following lumpectomy and axillary lymph node diss ection. The cumulative local recurrence rate as a first event, distant recurrence (i.e., occurrence of metastasis) rate, and overall mortali ty rate for the treatment groups were described by the Kaplan-Meier me thod and compared with the use of the logrank test. The Cox proportion al hazards model was used to adjust the observed treatment effect for the influence of various prognostic factors (patient age, tumor size, estrogen receptor level, and tumor histology) at study entry on the ou tcomes of local breast recurrence, distant recurrence, and overall mor tality. All P values resulted from the use of two-tailed statistical t ests. Results: One hundred forty eight (35%) of the nonirradiated pati ents and 47 (11%) of the irradiated patients developed recurrent cance r in the breast (relative risk for patients in the former versus the l atter group = 4.0; 95% confidence interval = 2.83-5.65; P<.0001). Nine ty-nine (24%) of the patients in the former group have died compared w ith 87 (21%) in the latter group. Age (<50 years), tumor size (>2 cm), and tumor nuclear grade (poor) continued to be important predictors f or local breast relapse. On the basis of these factors, we were unable to identify a subgroup of patients with a very low risk for local bre ast cancer recurrence. Tumor nuclear grade, as previously reported, an d tumor size were important predictors for mortality. Conclusions: Bre ast irradiation was shown to reduce cancer recurrence in the breast, b ut there was no statistically significant reduction in mortality. A su bgroup of patients with a very low risk for local breast recurrence wh o might not require radiation therapy was not identified.