Initial Outcomes with an Image-Guided Five Fraction Accelerated Partial-Breast Irradiation Regimen Delivered with IMRT

Abstract

Accelerated partial breast irradiation (APBI) offers the ability to decrease treatment duration, while potentially reducing toxicities and improving cosmetic outcomes. The purpose of this study is to examine outcomes with a five fraction image-guided APBI regimen delivered with IMRT. We reviewed an IRB-approved database of patients who were treated with five fractions APBI utilizing IMRT. Patients underwent CT simulation with active breathing control (ABC) to limit breast motion during treatment. The seroma cavity and surgical clips were contoured as the CTV with a 1 cm PTV expansion limited by 3 mm from the skin and chest wall (as compared to Livi et al. which utilized a 1 cm CTV expansion on the surgical clips and an additional 1 cm for PTV limited to 4 mm inside the lung and 3 mm from the skin). Thirty Gy in 5 fractions was delivered with 2-3 VMAT arcs every other day. Cone beam CT was performed at each fraction. A total of 34 patients were treated between 2015 and 2018. Median follow up was 4.6 months (range, 0.3-29.5 months). The median age was 64 years (range, 47-78 years) and the median BMI was 32.7 (range, 20.6-47.7). With respect to tumor stage, 5 patients had DCIS, 5 were T1a, 14 T1b, and 10 T1c, with all patients being node negative. A total of three patients received chemotherapy and 21 patients received endocrine therapy with all patients being ER+. Dosimetric analysis demonstrated an average mean heart dose (MHD) of 0.65 Gy (standard deviation [SD]: 0.5, median MHD: 0.57, range: 0.1-2.0) for all patients. Average MHD among patients treated to the right breast (n=20) was 0.57 Gy (SD: 0.5, median MHD: 0.45, range, 0.1-1.8), and for those treated to the left breast (n=14) it was 0.77 Gy, (SD: 0.5, median MDH: 0.67, range, 0.2-2.0 Gy). With respect to acute toxicity, 8 patients (23.5%) had grade I dermatitis and 6 patients (17.6%) experienced grade I fatigue. No grade II or higher acute toxicities were observed. Among the 24 patients with follow up to assess chronic toxicity (at least to 3 month post-treatment visit), 6 patients (25.0%) had grade I dermatitis, and none had grade 1 or higher telangiectasia or lymphedema. As compared to 3D-CRT whole breast irradiation with or without boost, the 5 fraction APBI IMRT regimen reduced cost by $947-$2,645 as determined by reimbursement. Image- guided APBI utilizing IMRT was well tolerated by patients with minimal acute and chronic toxicities to date. Further follow up is required to evaluate long term outcomes. A 5 fraction IMRT regimen represents a cost savings as compared to 3D-CRT whole breast irradiation.