Radiotherapy Modality and Primary Tumor Type as Determinants of Outcomes in Brain Metastases: A Retrospective Study of 734 Patients.

Background and Objectives: Radiotherapy (RT) is a standard component of palliative treatment for brain metastases. The aim of this retrospective analysis of consecutive patients treated between 2017 and 2023 is to analyze overall survival after brain radiotherapy depending on the type of radiotherapy delivered and to monitor the shift from whole-brain radiotherapy (WBRT) to stereotactic radiotherapy (SRS/FSRT) in real-world practice before the era of routinely used modern brain-penetrant targeted therapy. Materials and Methods: A total of 734 patients treated with radiotherapy for brain metastases were analyzed. Clinical data were collected via an electronic hospital information system and radiotherapy details were obtained using the Eclipse™ treatment planning system. The survival analysis divides patients according to cancer types and according to the RT technique used. Results: A total of 734 patients (median age 65.2 years; 50.5% women) were analyzed, with 104 undergoing more than one course of radiotherapy. Lung cancer (42.3%) and breast cancer (17.2%) were the most common primary diagnoses. Median overall survival (OS) after radiotherapy for the entire cohort was 2.8 months (2.6-3.2 months). Survival varied by radiotherapy technique: 2 months for WBRT-based approaches, 5.7 months for stereotactic radiotherapy (SRS/FSRT), and 7 months for combined WBRT and stereotactic treatment. Breast cancer patients had the longest median OS (3.6 months), with substantially improved outcomes in those treated with stereotactic or combined approaches (12.8 and 11.9 months, respectively). A decline in treated patients was observed during the COVID-19 pandemic (notably in 2021) and a consistent increase in the use of stereotactic techniques between 2017 and 2023 was noted. Conclusions: A wide range of radiotherapy techniques are used in the treatment of brain metastases with the primary concern being the prognosis and diagnosis of a patient. A clearly identifiable trend is a shift away from WBRT toward an increased use of targeted stereotactic irradiation techniques for brain lesions. Overall survival varies significantly across primary sites with most favorable outcomes in breast cancer patients irradiated with SRS/FSRT.