Six-Year Results From a Prospective Phase 2 Trial of 10-Fraction Hypofractionated Radiation Therapy in Locally Advanced Breast Cancer.

Abstract

We report the 6-year results of a phase 2 study on hypofractionated radiation therapy targeting the primary and regional lymph nodes in 10 fractions. A schedule of 34 Gy/10 fractions/2 weeks to the whole breast/chest wall and the draining lymph nodes was used. Both acute and late toxicities were collected. All patients 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 radiation therapy (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. From February 2015 to March 2019, 59 women (median age, 60 years and IQR, 48.3-68.8 years) 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 locoregional 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 patient, 1.7%), telangiectasia (1 patient, 1.7%), and lymphoedema (1 patient, 1.7%). One patient (1.7%) experienced grade 3 breast retraction at 36 months fup. The cosmetic outcome resulted in being 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 and overall survival rates were 88% and 94.4%, respectively. Our results support the activity of a 10-fractions hypo-RT schedule targeting the primary site as well as the draining lymph node stations after surgery for locally advanced breast cancer.