Local control, toxicity, and cosmesis in women younger than 50 enrolled onto the American Society of Breast Surgeons MammoSite Radiation Therapy System registry trial.

BACKGROUND: The American Society of Breast Surgeons enrolled women onto a registry trial to prospectively study patients treated with the MammoSite Radiation Therapy System (RTS) breast brachytherapy device. This report examines local recurrence (LR), toxicity, and cosmesis as a function of age in women enrolled onto the trial.

METHODS: A total of 1449 primary early-stage breast cancers were treated in 1440 women. Of these, 130 occurred in women younger than 50 years of age. Fisher's exact test was performed to correlate age (<50 vs. > or = 50 years) with toxicity and with cosmesis. The association of age with LR failure times was investigated by fitting a parametric model.

RESULTS: Women younger than 50 were more likely to develop fat necrosis: 4.6% (6 of 130) vs. 1.8% (24 of 1319) (P = .0456). Other toxicities were comparable. At 2 years, cosmesis was excellent or good in 87% of assessable women aged <50 years (n = 74) and in 94% of assessable older women (n = 751) (P = .0197). At 3 years, this difference disappeared: excellent or good in 90% (56 of 62) of younger women vs. 93% (573 of 614) of older women (P = .2902). The crude LR rate for the group was 1.7% (25 of 1449). There was no statistically significant difference in LR as a function of age. In women <50, 3.1% (4 of 130) developed a LR; in the older patients, 1.6% (21 of 1319) developed LR (3-year actuarial LR rates, 2.9% vs. 1.7%, respectively; P = .2284).

CONCLUSIONS: Accelerated partial breast irradiation with the MammoSite RTS results in low toxicity and produces similar cosmesis and local control at 3 years in women younger than 50 when compared with older women.