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Delaying Radiotherapy to Allow Adjuvant Chemotherapy Not Shown to Increase Ipsilateral Recurrence Risk

Delaying Radiotherapy to Allow Adjuvant Chemotherapy Not Shown to Increase Ipsilateral Recurrence Risk

PITTSBURGH—Although not designed specifically to answer the question, NSABP B-15 and B-16 provide no evidence that delay in radiation therapy, to allow administration of adjuvant chemotherapy, increases the risk of ipsilateral breast cancer recurrence in node-positive patients undergoing breast-conserving surgery. E.P. Mamounas, MD, presented the updated results of these two trials at a general session of the San Antonio meeting. Dr. Mamounas is with the NSABP at the University of Pittsburgh, and is also medical director of the Mount Sinai Center for Breast Health, Beachwood, Ohio.

Patients were allocated to one or the other protocol, both of which were run at the same time, according to tamoxifen (Nolvadex) responsiveness. B-15 included tamoxifen-unresponsive patients less than 49 years of age and between 50 and 59 years of age if progesterone-receptor (PR) negative.

They were randomized into three groups: AC (Adriamycin, cyclophosphamide) with a 12-week delay in radiation therapy; CMF (cyclophosphamide, methotrexate, fluorouracil) with a 4-week delay; and AC followed in 6 months by CMF, with a 12-week delay. Of 2,294 patients enrolled in B-15, 624 underwent lumpectomy and radiation.

B-16 included tamoxifen-responsive patients between 60 and 70 years of age and also those between 50 and 59 years of age if PR positive. They were randomized to receive tamoxifen alone, with no resulting delay in radiation therapy, or AC plus tamoxifen, with a 12-week delay in radiation. Of 833 patients in B-16, 228 had lumpectomy and radiation.

The results at 10 years continue to show no disease-free or overall survival difference between the three arms of treatment in B-15 for all patients or for lumpectomy patients. There continues to be a disease-free survival and overall survival advantage of AC plus tamoxifen over tamoxifen alone in B-16, for all patients and for lumpectomy patients.

An analysis of the cumulative incidence of ipsilateral breast tumor recurrence at 10 years showed no difference among the three treatment groups in protocol B-15, or between tamoxifen alone and AC plus tamoxifen in the B-16 study.

In addition, Dr. Mamounas said, an examination of the incidence of ipsilateral recurrence according to tumor size and nodal status showed no interaction in either study.

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