Preliminary toxicity results using partial breast 3D-CRT with once daily hypo-fractionation and deep inspiratory breath hold

Roman O. Kowalchuk, Kara D. Romano, Daniel M. Trifiletti, Sunil W. Dutta, Timothy N. Showalter, Monica M. Morris

To evaluate the clinical outcomes of patients treated with 3D conformal Hypo-fractionated, deep Inspiratory breath-hold (DIBH), Partial breast radiotherapy, termed "HIP." HIP was implemented to merge the schedule of once-daily breast hypofractionation with partial breast treatment. We identified 38 breast cancers in 37 patients from 2013 to 2014 treated at our institution with HIP following lumpectomy for early stage breast cancer. Patients received a hypo-fractionated course (≤ 20 fractions) of once daily radiation to the partial breast (lumpectomy cavity + margin) utilizing DIBH regardless of laterality. Clinical and treatment-related characteristics were obtained, including target volume and organ at risk (OAR) dosimetric characteristics. Patients were followed clinically and with at least yearly mammograms for up to 36 months (range 5-36 months). Acute and late toxicity was scored using the Common Terminology Criteria for Adverse Events (CTCAE) v4.03. Patients received a median dose of 42.56 Gy in 16 Fractions (Fx) (range 40.05-53.2 Gy; and 15-20 Fx). OAR doses were low, with a mean heart dose of 0.37 Gy, an ipsilateral lung V20 mean of 4%, and a contralateral lung V5 of 1%. Acute toxicity (≤ grade 2) was present in 79% (n = 30) of the cases, with dermatitis being the most common finding (63%). Late grade 1-2 toxicity was present in 42% (n = 16) of the cases, with hyperpigmentation being the most common finding (n = 9). There were no severe acute or late toxicities (≥ grade 3). At a median follow up of 21 months, there were no local, regional, or distant failures. We report limited toxicity in this low risk cohort of patients with early stage breast cancer treated with HIP, a unique and logical combination of 3-D conformal external beam radiotherapy, moderate hypo-fractionation, and DIBH.