No abstract

92 Background: Limited data are available on the treatment of ductal carcinoma in situ (DCIS) with accelerated partial breast irradiation (APBI). The American Society for Radiation Oncology (ASTRO) consensus guidelines on APBI classify patients with DCIS as “cautionary”. We present the largest series of DCIS patients reported to date treated with APBI using strut-based brachytherapy. Methods: The SAVI Collaborative Research Group (SCRG) database was used to identify APBI patients with DCIS at 15 institutions treated with strut-based brachytherapy. All patients had a histologic diagnosis of DCIS and received monotherapy APBI (34 Gy in 10 fractions). Data on patient age and margin status, implant dosimetry, device size, disease status and toxicity in this population were analyzed. Results: From 2007-2011, 321 patients (322 breasts) with DCIS received APBI using strut-based brachytherapy. Patient ages ranged from 40-88 with a median age of 62. 51 patients were under 50 years of age. Detailed dosimetry data were reported on 245 patients. Long-term follow up was available on 221 breasts (median F/U = 25 months). Sixty patients have been followed for >3 years. Skin spacing was a challenge in a significant number of patients including 52 with skin spacing ≤ 5mm and 20 with skin spacing ≤ 3mm. Median maximum skin dose in those patient groups were 87% and 84% of prescription dose (PD), respectively. Overall reported dosimetry (n=245) was excellent: median percent of target volume receiving 90% PD was 96.9%, median maximum skin dose was 83.2%, V150% and V200% (volume at 150% and 200% PD) were 25.2 cc and 12.7 cc respectively. The ipsilateral recurrence rate was 2.2% (1.1% TR/MM). Late toxicity (grade ≥ 2) was low: hyperpigmentation = 0.0%, telangiectasias =1.4%, seroma = 3.2%, and fat necrosis in 1.8%. Conclusions: APBI using strut-based brachytherapy appears to be an effective treatment for patients with DCIS with acceptably low ipsilateral breast recurrence rates and low rates of late toxicity. 52 patients in our series had skin spacing 5 mm or less. APBI using brachytherapy may not have been possible for these women with other single-entry devices.