51P - Four-year outcomes of hypofractionated postmastectomy radiation therapy of 39 Gy in 13 fractionations

Background

Four-year outcomes of hypofractionated postmastectomy radiation therapy of 39 Gy in 13. Fractionations to investigate early and four year late side effects of hypofractionated postmastectomy radiation therapy (HFRT-PM) of 39 Gy in 13 fractions over 3 weeks.

Methods

We retrospectively analyzed characteristics and outcomes of patients with stage II to III breast cancer treated with HFRT-PM between February 2019 and February 2023 during the COVID-19 pandemic. The selected patients did not have any previously diagnosed heart or lung disease. Treatment provided in 13 fractions of 3 Gy per fraction. The treatment techniques were applied by using 3-dimensional conformal radiation therapy and IMRT of the chest wall with regional nodal volume if required. The end point was freedom from any grade 3 or higher toxicities.

Results

We identified 730 patients with a median follow-up of 4 year. About two-third of the patient (66.6%) had the disease located in the left side. Regional nodal irradiation was done in 84.1% of patients. In multivariate analysis, regional lymph node involvement (≥4 nodes) was associated with worse locoregional control (hazard ratio, 1.68; 95% confidence interval, 1.06-2.67; P = .03) and overall survival (hazard ratio, 2.16; 95% confidence interval, 1.59-2.95; P < .001). The toxicities were acceptable. After a four-year follow -up, there are no grade 3 or 4 toxicities. The incidence of early skin reactions (13% grade 2) cardiac disorders (1.5%), and symptomatic lung fibrosis (1.7%) was low during follow-up. The cumulative rate of arm lymphedema was 2.1% and considered severe in 40 patients (0.05%).

Conclusions

The early results of this study show that HFRT-PM of 39 Gy in 13 fractions over 3 weeks seems safe, but long-term results need to be observed and highlighting the need for long-term follow-up and for randomized trials for hypofractionated radiation therapy postmastectomy especially for young patients.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The author.

Funding

Has not received any funding.

Disclosure

The author has declared no conflicts of interest.