Effects of axillary dose restriction on plan quality and acute radiation dermatitis in breast cancer radiotherapy.

Abstract

Axillary dose restriction (ADR) is rarely implemented in breast cancer radiotherapy by radiation oncologists to minimize exposure to organs at risk (OARs), particularly the axilla. This prospective randomized controlled study aims to evaluate the efficacy of ADR in improving plan quality (PQ) and its impact on acute radiation dermatitis (ARD) in breast cancer radiotherapy. The study recruited breast cancer patients who required postoperative radiotherapy but did not have an indication for axillary irradiation. Delineation and dosimetric assessment of the axilla (Axilla Levels I-III and Axillary Cavity) were performed in all cases, with ADR implemented randomly. ADR involved restricting the mean axilla dose to 40-45 Gy during radiotherapy. The outcomes assessed included the ARD grades (both overall and axillary) and dose-volume parameters of PQ including skin V35. The study enrolled 87 patients, who were randomly divided into two groups: Group I (50 patients) received ADR, while Group C (37 patients) did not. ADR was found to be significantly associated with reduced exposure doses to the axilla and ipsilateral lung, specifically in patients with modified radical mastectomy (MRM). Results of other PQ parameters, such as D95, V93, V95, V100, V107 for the planning target volume (PTV), V30, Dmean for the heart, Dmax for the spinal cord, and V5 for the ipsilateral lung, demonstrated potential benefits in alleviating doses to these OARs while maintaining optimized PQ, although these results were not statistically significant. However, no statistically significant correlation between ADR and severe ARD (≥ Grade 2) or skin V35 was established, either in the total patient population or in subgroups. Additionally, a multivariable logistic regression for severe ARD was conducted, with ADR and skin V35 included as predictive factors. Only older age was found to be significantly associated with severe ARD. Implementing ADR in breast cancer radiotherapy not only protects the axilla and ipsilateral lung but also maintains optimized PQ, specifically in MRM patients, though it shows no evidence of alleviating ARD. Adopting ADR may be considered a valuable option in breast cancer radiotherapy.