Long-Term Radiographic Findings After Balloon-based Accelerated Partial Breast Irradiation

Abstract

Accelerated partial breast irradiation (APBI) offers patients the convenience of a shorter course of therapy with good clinical and cosmetic outcomes. While several retrospective institutional series have reported short term radiographic findings, including seroma, calcifications, and architectural distortion, less is known about long-term radiographic findings. The purpose of this study is to report long-term radiographic findings after treatment with balloon based APBI. Records of women treated with balloon based APBI from 2005-2012 at one institution were reviewed after IRB approval. All patients were treated with 34 Gy in 10 fractions. All patients had pre-treatment diagnostic imaging, with a minimum of 2 years of surveillance imaging. Post-treatment images of 129 patients were reviewed by one radiologist. The majority of surgical excisions were open cavity non-oncoplastic procedures. Univariate and multivariate analysis of factors leading to formation and resolution of seroma were performed in patients treated with lumpectomy and APBI. Median age at diagnosis was 62 years, and 89% were Stage 0-1. Median surgical excision volume was 108.9 cc (range 20.5-681.9). Number of margin re-excisions were 0, 1, 2+ in 36%, 40%, and 21% respectively. Median time from biopsy or segmental mastectomy to completion of RT was 1 month (range <1-4). Primary mode of imaging was mammogram. Median time from end of RT to first and last surveillance image was 6 and 54 months respectively. Median number of images was 7 (range 3-12). Time from end of RT to initial identification of seroma was 6.4 months (range 3-34). Seroma was identified in 98 (76%) patients, with median maximum diameter of 3.9 cm. Forty (41%) patients experienced resolution of seroma, at a median time of 29 months (range 6-74). Invasive or insitu pathology, body mass index, chemotherapy, multichannel device, and infection were not associated with formation or resolution of seroma. On univariate analysis, surgical excision volume was associated with seroma formation, and tumor stage and margin re-excision were significant on univariate and multivariate analysis. Seroma formation after APBI resolves around 2.5 years for many patients, but persists for others possibly due to primary tumor and surgical excision volumes. With revised criteria on the definition of positive margins, smaller volumes and fewer re-excisions may lead to decreased risk of seroma formation for future patients.