Influence of dose-volume and clinical parameters on Patient-Reported Skin Toxicities in Breast Cancer Radiotherapy

This study investigated the influence of dose-volume and clinical parameters on patient-reported outcomes (PROs) related to skin toxicities in breast cancer radiotherapy at the Department of Radiation Oncology, Medical University of Vienna / General Hospital Vienna. The following toxicities were included in the analysis: skin dryness, itching, radiation skin reaction, skin darkening, and breast swelling and tenderness. The PROs were collected on a 5-point scale for acute and long-term side effects up to 24 months after treatment. The patient cohort included three photon-based external beam radiation therapy techniques: Three-Dimensional Conformal Radiation Therapy (3D-CRT), Intensity Modulated Radiation Therapy (IMRT), and Volumetric Modulated Arc Therapy (VMAT). These techniques differ in beam number, orientation and modulation, which may influence skin dose and PROs. A boost, i.e., an additional radiation dose to the tumor bed, is also considered, following a recent transition from a sequential boost (SQB) to a simultaneous integrated boost (SIB).Additional clinical factors, including age, systemic therapies, prior surgery, and treatment laterality were also included in the analysis. Statistical testing methods were used to assess differences in dose metrics and side effects among treatment techniques and boost methods.Overall, more severe patient-reported skin toxicities were observed in groups treated with a SQB. The analysis revealed that a larger high-dose skin volume was associated with more worsening in acute side effects, while higher age reduced this risk. The relationship between high-dose skin volumes and skin toxicity was less pronounced than expected, as no correlation with late toxicities was observed for V40Gy.