Low-energy X-ray intraoperative radiotherapy for brain metastases: a systematic review of efficacy and safety.

PURPOSE: To evaluate the current use of intraoperative radiotherapy (IORT) in the treatment of brain metastases. METHODS: A systematic search of MEDLINE/PubMed, Embase, Cochrane Library, and Web of Science was conducted following PRISMA guidelines. Eligible studies included those reporting on the use of IORT for brain metastases, with data on patient demographics, treatment protocols, and clinical outcomes. Studies were screened and selected based on predefined inclusion and exclusion criteria. Data were extracted on study design, cohort size, IORT protocols, survival outcomes, and treatment-related complications. Quality assessments were performed using the NIH Quality Assessment Tool. RESULTS: Sixteen studies with 606 patients assessed the efficacy and safety of low-energy X-ray IORT for brain metastases. Median applicator size was 2 cm across studies (range of reported study medians, 1.5–5 cm). Local control rates at 1 year ranged from 84.2% to 98%, with most studies reporting rates above 87%. Distant brain control was more variable, ranging from 13% to 73.5% at 1 year. Overall survival at 1 year varied between 57.7% and 80%, with median survival times from 12.3 to 26.4 months. The incidence of radiation necrosis (RN) was generally low at 4.2%, in the newly diagnosed lesions, with a symptomatic RN rate of 0.77% among 259 new lesions. Overall reported rates of RN were low at 6.6%. Perioperative complication rates were also low, with the most common events being bleeding (3.9%) and infection (3.0%). CONCLUSION: IORT may offer effective local control for brain metastases, with a 1-year local control rate that seems to compare favorably to SRS, the current standard of care. Reported symptomatic RN rates were low, particularly in newly diagnosed lesions, although these observations are based largely on noncomparative observational studies. Further research is needed to clarify comparative effectiveness, safety, and patient selection.