Abstract P5-14-06: Outcomes in 500 patients from a large, retrospective study of APBI with a strut-based breast brachytherapy applicator

Purpose/Objectives:

The SAVI Collaborative Research Group (SCRG) is a coalition of 14 institutions who have retrospectively compiled a large database of APBI patients treated with a strut-based brachytherapy device (SAVI). This report details the findings of statistical correlations between numerous dosimetric variables and cosmetic outcome.

Materials/Methods:

The SCRG study enrolled 1005 patients. A subset of patients with complete dosimetry and more than 1 year of follow-up by a radiation oncologist were analyzed for toxicity, cosmesis and recurrence/survival. Dosimetric parameters were tabulated for patients, including: V90, V95, V100, V150, V200, skin spacing (skin-bridge), maximum skin dose, tumor size, PTV-Eval volume and applicator size (model). Toxicity (e.g., telangiectasia, fibrosis, fat necrosis, seroma) were graded by physicians for patients with at least 1 year of follow-up (up to 6 years) using the CTCAE v3 Scale and fat necrosis using a simplified CTCAE scale (Grade 1 asymptomatic but seen on imaging, grade 2 symptomatic without intervention, & grade 3 required intervention).

Results:

Median follow up in this cohort was 29.2 months (range 2.4 to 72.2 months). Follow up was >2 yr and >3 yr for 323 and 191 subjects, respectively. Overall, in 500 subjects the late toxicity (grade ≥2) rates were less than 5% during follow up: telangiectasia 1.0%, fibrosis 4.1%, seroma 2.9% and fat necrosis 0.6%. Cosmesis was reported at various post-APBI follow-up visits following treatment completion (6, 12, 24, 36, 48 & 60+ months). For the 6 and 12 month intervals, 98% (n = 122) and 97% (n = 262) were reported excellent or good (E/G), respectively. At 24, 36, 48 and 60 month intervals, the E/G rates were 93% (n = 184), 90% (n = 98), 100% (n = 41) and 94% (n = 15), respectively. The raw rates of ipsilateral breast tumor recurrence (IBTR) and TR/MM were 1.6% (n = 8) and 1.2% (n = 6), respectively, in 500 patients with >1 year of follow up. The 1- and 2-year actuarial rates of overall survival and disease-free survival were: 1-year, 99.6% & 99.4%, resp. and 2-year, 99.2% & 96.7%.

Conclusions:

APBI treatment with the strut-based applicators was well-tolerated, demonstrated low toxicity rates, favorable cosmetic outcomes and excellent local control over the follow-up to date. Patients with challenging breast anatomy were successfully treated with strut-based devices.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-14-06.