6- YEAR RESULTS FROM A PROSPECTIVE PHASE II TRIAL OF TEN-FRACTION HYPOFRACTIONATED RADIOTHERAPY IN LOCALLY ADVANCED BREAST CANCER.

Abstract

PURPOSE We report the 6-year results of a phase II study on hypofractionated radiotherapy (HFRT) targeting the primary and regional lymph nodes in ten fractions (fxs). MATERIALS AND METHODS A schedule of 34 Gy/10 fxs/2 wks to the whole breast/chest wall and to the draining lymph nodes was used. Both acute and late toxicities were collected. All pts but those who underwent mastectomy without reconstruction or with temporary expander were asked to rate their cosmetic outcome according to the Harvard scale. Toxicity was assessed weekly during RT and then at each follow-up (fup) examination. Cancer related endpoints were evaluated from the date of RT start to the diagnosis of local relapse/distant metastases or the last fup respectively. RESULTS 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%) were accrued. One patient was lost to fup immediately after the end of RT. At the median fup of 77.11 months (range: 24-102 months), the cumulative incidence of any grade loco-regional late toxicity estimated with the Kaplan-Meier method is 43.4% (95%CI) (30.0% and 46.1% for patients undergone mastectomy and lumpectomy, respectively). Peak- 2 events have been observed for fibrosis (1 pt, 1.7%), telangiectasia (1 pts, 1.7%) and lymphoedema (1 patient, 1.7%). One patient (1.7%) experienced grade 3 breast retraction at 36 month fup. The cosmetic outcome resulted to be excellent, good, fair and poor in 61.7%, 25%, 7.6% and 5.7%, respectively. At 72 months the specific-disease free survival was 96.5%; distant metastasis-free survival (DMFS) and OS rates were 88% and 94.4% respectively. CONCLUSIONS Our results support the activity of a 10-fxs Hypo-RT schedule targeting the primary site as well as the draining lymph node stations after surgery for locally advanced BC.