Clinical outcomes and dosimetric study of hypofractionated Helical TomoTherapy in breast cancer patients.

We present a single center's experience of treatment outcomes and dosimetric parameters for breast cancer patients treated with hypofractionated Helical TomoTherapy (HT). This is a retrospective study of one hundred and thirty-six patients with invasive breast cancer treated between March 2012 and October 2016. Dosimetric parameters and 3-year loco-regional failure free survival (LRFFS) were analyzed. Dose to ipsilateral lung, heart and contralateral breast as well as acute and late toxicities were recorded. The median follow-up time is 45 months (range: 5-83). Two patients had loco-regional failure. The 3-year LRFFS was 99%. Acute grade 1 and 2 skin toxicities occurred in 95% and 1%, respectively. Coverage of the target volumes was achieved with the mean ± standard deviation (SD) of homogeneity and conformity index being 0.1 ± 0.04, and 0.8 ± 0.07, respectively. Dose to ipsilateral lung, contralateral breast, and heart was also within the limited constraints regardless of the complexity of target volumes. Only two percent of patients experienced late grade 2 skin toxicity. No late grade 2 subcutaneous tissue toxicity was found. Nine percent of patients developed late grade 1 lung toxicity. Hypofractionated radiotherapy using Helical TomoTherapy in breast irradiation provides excellent 3-year LRFFS and minimal acute and late toxicities. A careful, longer follow-up of healthy tissue effects to lung, heart, and contralateral breast is warranted