Treatment efficacy with accelerated partial breast irradiation (APBI): final analysis of the American Society of Breast Surgeons MammoSite(®) breast brachytherapy registry trial.

BACKGROUND: The purpose of this study was to examine data on treatment efficacy, cosmesis and toxicities for the final analysis of the American Society of Breast Surgeons MammoSite(®) breast brachytherapy registry trial. METHODS: A total of 1,449 cases of early-stage breast cancer underwent breast conserving therapy. The single-lumen MammoSite(®) device was used to deliver accelerated partial breast irradiation (APBI) (34 Gy in 3.4 Gy fractions). Of these, 1,255 cases (87 %) had invasive breast cancer (IBC) and 194 cases had DCIS. Median follow-up was 63.1 months with 45 % of all patients having follow-up of 6 years or longer. RESULTS: There were 41 cases (2.8 %) that developed an ipsilateral breast tumor recurrence (IBTR) for a 5-year actuarial rate of 3.8 % (3.7 % for IBC and 4.1 % for DCIS). Tumor size (odds ratio [OR] = 1.1, p = 0.03) and estrogen receptor negativity (OR = 3.0, p = 0.0009) were associated with IBTR, while a trend was noted for positive margins (OR = 2.0, p = 0.06) and cautionary/unsuitable status compared with suitable status (OR = 1.8, p = 0.07). The percentage of patients with excellent/good cosmetic results at 60, 72, and 84 months was 91.3, 90.5, and 90.6 %, respectively. The overall rates of fat necrosis and infections remained low at 2.5 and 9.6 % with few late toxicity events beyond 2 years. The overall symptomatic seroma rate was 13.4 and 0.6 % beyond 2 years. CONCLUSIONS: The final analysis of treatment efficacy, cosmesis, and toxicity from the American Society of Breast Surgeons MammoSite(®) breast brachytherapy registry trial confirms previously noted excellent results and compares favorably with other forms of APBI with similar follow-up and to outcomes seen in selected patients treated with whole breast irradiation.

Should ductal carcinoma-in-situ (DCIS) be removed from the ASTRO consensus panel cautionary group for off-protocol use of accelerated partial breast irradiation (APBI)? A pooled analysis of outcomes for 300 patients with DCIS treated with APBI.

PURPOSE: To analyze outcomes in patients with ductal carcinoma-in-situ (DCIS) treated with accelerated partial breast irradiation (APBI) within a pooled set of patients. METHODS: A total of 300 women with DCIS underwent APBI between April 1993 and November 2010 as part of American Society of Breast Surgeons MammoSite Registry Trial (n = 192) or at William Beaumont Hospital (n = 108). Patients with pure DCIS <3 cm (n = 125) were assigned to the cautionary risk group per American Society of Radiation Oncology consensus panel guidelines for off-protocol use of APBI and analyzed compared to a pooled invasive suitable (n = 653) risk group and pooled invasive suitable/cautionary (n = 1,298) risk group. RESULTS: The rate of ipsilateral breast tumor recurrence (IBTR) for all 300 DCIS patients was 2.6 % at 5 years with no regional recurrences, while cause-specific survival was 99.5 % and overall survival (OS) was 96.4 %. When comparing the cautionary DCIS group to the invasive suitable/cautionary group, no difference in IBTR was noted (2.6 vs. 3.1 %, P = 0.90) with significant improvements in distant metastases (0 vs. 2.5 %, P = 0.05), disease-free survival (98.5 vs. 94.4 %, P = 0.05), and OS (95.7 vs. 90.8 %, P = 0.03) noted for DCIS patients. When comparing cautionary DCIS patients to invasive suitable patients, no difference in IBTR were noted (2.6 vs. 2.4 %, P = 0.76), while improved OS for DCIS patients was noted (95.7 vs. 90.9 %, P = 0.02). CONCLUSIONS: This analysis of the largest cohort of patients with DCIS treated with APBI supports previously reported excellent outcomes; as a result of small numbers of events, further data are necessary to confirm these findings.