Evaluating of radiation-induced cerebral contrast enhancements in brain metastases: analysis of incidence and risk predictors.

Radiation-induced cerebral contrast enhancements (RICE) are frequent after photon and particularly proton radiation therapy (RT) and are associated with a significant risk for neurologic morbidity. While stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) provide high rates of local control (LC), RICE remains a significant concern that may impact patient outcomes and quality of life. This study aims to assess the incidence, risk factors, and clinical implications of RICE in patients treated with SRS or FSRT for brain metastases (BMs). A retrospective analysis was conducted on 175 patients with 330 BMs treated between October 2015 and November 2023. Median follow-up (FU) was 17 months. The incidence of RICE was determined, and potential predictive factors were evaluated using univariate Cox regression analysis. RICE was identified in 8 patients with 10 lesions (3%). Systemic therapy without immunotherapy (IT) was found to be a significant predictor of RICE (HR = 4.161,  p= 0.027). No significant association was observed between the occurrence of RICE and overall survival (OS), indicating that while RICE is a treatment-related adverse event, it does not appear to significantly influence long-term survival. RICE occurs in a small subset of patients treated with SRS or FSRT. Systemic therapy without IT significantly increases the risk, underscoring the need for careful treatment planning and patient selection. While necrosis does not impact overall survival, its potential effects on neurological function and quality of life warrant continued research into preventive and management strategies.