Local Control, Toxicity, and Cosmesis in Women Younger Than 50 Enrolled Onto the American Society of Breast Surgeons MammoSite Radiation Therapy System Registry Trial

Abstract

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. 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. 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). 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.