Ten Fraction Adjuvant Hypofractionated Radiotherapy in Node Positive Breast Cancer: 3 Year-Follow-Up of a Phase II Toxicity Study

Abstract

Post-operative loco-regional (LR) hypofractionated radiotherapy (Hypo-RT) is an attractive approach in locally advanced breast cancer (LABC). The aim of this study is to report the preliminary results of a 10 fraction hypofractionated schedule in patients (pts) with resected LABC.The present is a single arm phase II study assessing toxicity outcomes after 34 Gy/10 fxs/2 wks to the whole breast/chest wall and to the draining lymph nodes; an optional single fraction 8 Gy boost was administered with electrons to the tumor bed in patients who had undergone conservative surgery. Both acute (CTCAE v4.0) and late (LENT/SOMA) toxicities were collected. All pts but those who underwent mastectomy without reconstruction or with temporary expander were also asked to rate their cosmetic outcome according to the Harvard scale. Toxicity was assessed weekly during RT and then at each follow-up examination (1, 3, 6 months and then yearly).From February 2015 to March 2019, 59 women (median age 60 yrs, IQR: 48.3-68.8 yrs) with stage II to IIIA breast cancer who underwent axillary dissection and conservative surgery (83%) or mastectomy (17%) entered the study. One patient refused follow up immediately after the end of RT. Of the 58 evaluable pts, 56 underwent neo-adjuvant (41%) or adjuvant (59%) chemotherapy. Trastuzumab was administered concomitant with RT in all HER2 positive pts (25%). RT was delivered initially with a conformal 3D-CRT (32.8%) and then with an optimized IMRT (67.2%) technique to improve the dose distribution. A deep inspiration breath hold technique was used in compliant left-sided LABC pts (48.4%). All ptscompleted treatment as planned. At a median follow up of 42.3 months (IQR 31.4-57.2 mths), no locoregional failures have been observed. Peak acute toxicity was as follows: grade 0, 30 pts (51.7%); grade 1, 25 pts (43.1%); grade 2, 3 pts (5.2%); no grade > 2 toxicity was recorded. Regarding late toxicity, peak 2 events were found for fibrosis (1 pt, 1.7%), telangiectasia (1 pts, 1.7%); lymphedema (1 pt, 1.7%). One patient (1.7%) experienced grade 3 breast retraction. No other grade 2+ events were reported. Of eligible patients (N = 51) patient-reported cosmetic outcome was excellent, good, fair and poor in 59%, 23.5%, 11.7% and 5.8%, respectively.These preliminary data support the feasibility and tolerability of our 10-fraction fractionation schedule targeting the primary site as well as the draining lymph node stations after surgery for LABC.