Abstract 169P
Background
Hypofractionation—delivering higher dosages per fraction in a shorter time—is common now. Hypofractionated radiotherapy for whole breast irradiation is preferred over CF-PMRT according to multiple randomized trials showing equivalent efficacy and safety. Post-mastectomy breast cancer hypofractionation is understudied. HF-PMRT with regional nodal irradiation has equal efficacy and toxicity to traditional fractionation (CF-PMRT).
Methods
87 of 92 histopathologically confirmed locally advanced breast cancer patients who underwent modified radical mastectomy and appropriate surgical axillary staging, WHO performance status 0-2, were eligible for this prospective, non-randomized trial from 2014–2015 and 2019–2021. HF-PMRT was 43.2 Gy in 16 fractions (2.7 Gy/fraction) or CF-PMRT was 50-50.4 Gy in 1.8-2.0 Gy/fraction to the chest wall and regional nodes with scar boost for high-risk patients. Locoregional recurrence-free survival. Overall survival, distant metastases control, disease-free survival, acute and late toxicity were secondary objectives.
Results
Stage II and menopausal cases dominated HF-PMRT. Same age, co-morbidities, symptoms, and performance. HF-PMRT had 23.5 months of median follow-up and CF-PMRT 23. (10-39). HF-PMRT had 68% interruption days versus 8 for CF-PMRT (p<0.003). HF-PMRT had 86.3% two-year survival, CF-PMRT 100%, p = 0.126. The longer-follow-up 2014-2015 cohort showed three HF-PMRT deaths (13.6%) and no CF-PMRT deaths (1 patient died of brain metastasis after 26.9 months, another died of unknown cause after 47.5 months, and 1 died due to cardiopulmonary arrest after 17.9 months follow-up). HF-PMRT showed 68.18% disease-free survival, CF-PMRT 73.33%. No locoregional recurrence was reported. HF-PMRT showed 86.96% grade 1 acute cutaneous toxicity, CF-PMRT 53.6%. Six (8.70%) HF-PMRT and 14 (34.15%) CF-PMRT patients exhibited Grade 2 skin toxicity. Five (12.20%) CF-PMRT patients exhibited Grade 3 acute cutaneous toxicity, compared to none in HF-PMRT, p = 0.001.
Conclusions
This interim analysis suggests HF-PMRT is a promising therapeutic option. This observational study follows all patients for five years.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.