Impact of Radiotherapy Volumes on Late-Term Cosmetic Outcomes and Quality of Life in Patients With Unifocal and Multifocal/Multicentric Breast Cancer After Breast-Conserving Surgery.

Objective: Breast-conserving surgery (BCS) followed by radiotherapy (RT) is the standard treatment for early-stage breast cancer. The use of an additional RT dose (boost) to the tumour bed improves local control but may worsen quality of life (QOL) and cosmetic results. Multifocal/multicentric tumours (MMTs) pose a challenge as they require larger boost volumes. This study investigated the impact of RT volumes on late-term cosmetic outcomes and QOL in patients with unifocal and MMTs who underwent adjuvant RT after BCS. Materials and Methods: Retrospective data of 367 patients who underwent BCS between 2012 and 2014 were reviewed. A cohort of 121 patients with at least six months of completed RT were prospectively included in the study. Cosmetic results were evaluated using a modified scoring system, and QOL was assessed using The European Cancer Treatment and Organization Committee tools. Results: The results showed that the inclusion of regional lymphatics in the RT treatment field significantly affected QOL, particularly in terms of role functioning and social functioning. Higher boost volume ratios were associated with increased pain-related symptoms. However, the presence of MMTs did not significantly affect cosmetic outcomes compared to unifocal tumours. Conclusion: The size of the boost and inclusion of regional lymphatics in RT significantly impact QOL in patients undergoing BCS. Tumour foci number does not affect cosmetic outcomes. These findings emphasize the need for careful consideration of RT volumes to minimize long-term adverse effects on QOL. Future prospective studies should evaluate early side effects and baseline QOL scores to provide a comprehensive assessment.