Outcomes of Adjuvant Hypofractionated Radiotherapy in the Treatment of Post-Mastectomy Breast Cancer Patients.

Abstract

PURPOSE/OBJECTIVE(S)\nThis is a retrospective study to assess loco-regional control, disease free survival (DFS) and overall survival (OS) of adjuvant hypofractionated radiotherapy (HF RT) compared to conventionally fractionated radiotherapy (CF RT) in post-mastectomy breast cancer patients.\n\n\nMATERIALS/METHODS\nFrom Jan 2007 to Dec 2016, 1077 women were diagnosed with breast cancer and received adjuvant post-mastectomy radiotherapy (PMRT) in the clinical oncology department of one institution.\n\n\nRESULTS\nWe had 477 patients treated with CF RT regimen and 600 patients treated with HF RT regimen following mastectomy. The median age at diagnosis was 49 years, 48 years in (CF RT) and 50 years in (HF RT); P\u202f=\u202f0.011. Fifty percent of all study patients had stage III disease. Of all study patients, 93.4% received chemotherapy and 82.8% received hormonal treatment. In the HF RT group, 68 % started RT after more than 6 months from surgery date, while 53.4 % in the CF RT group started RT after more than 6 months following surgery; P < 0.001. The highest proportion (83.5 %) of patients received regional nodal irradiation (RNI) in the HF RT group versus 75.2 % in the CF RT group; P\u202f=\u202f0.003. HF RT dose was mostly 40 Gy/15 Fx (57.8%), and 42 Gy/ 16 Fx (36.5%). Radiotherapy was delivered by 3-D Conformal radiotherapy. The majority of patients had no delay or delay 5 days or less due to treatment interruption during course; 74.2% in CFRT and 78.1% in HFRT group; P < 0.001. The HF RT group showed lower incidence of overall relapse; 20% vs 30.6% in CF RT group (OR 0.56, 95% CI 0.43 - 0.75) P < 0.001, loco-regional failure 5.8% vs 10.5% in CF RT group (OR 0.53, 95% CI 0.34 - 0.83) P\u202f=\u202f0.005, and distant metastasis 16.7% vs 25.8% in CF RT group (OR 0.58, 95% CI 0.43 - 0.77) P < 0.001. The 5-year DFS in the CF RT group was 71.7%, while in the HF RT regimen group was 75.4% (P\u202f=\u202f0.049). The 5-year OS in the CF RT group was 86.6%, while in the HF RT regimen group was 88% (P\u202f=\u202f0.027). Reported late side effects included cardiac events (5 patients in CFRT and 1 patient in HF RT group), lung fibrosis (11 patients in CFRT and 9 patients in HF RT group) and rib fracture in 1 patient in CF RT group CONCLUSION: Our data suggest that adjuvant HF RT may offer slightly better DFS and OS in post-mastectomy patients without increasing late toxicity.