Low-Energy X-Ray Intraoperative Radiation Therapy (Lex-IORT) for Resected Brain Metastases: A Single-Institution Experience

Simple Summary Advances in systemic cancer management have improved survival for numerous types of solid cancer; therefore, the number of patients harboring BM is increasing. According to established guidelines, resection should be carried out in patients with single brain metastases and controlled primary disease or when histopathologic diagnosis is crucial for decision-making in cancer management. Post-surgery rates of local recurrence are high; hence, adjuvant local radiation therapy (RT) is indicated to improve outcomes. So far, there is no standard of care regarding dose and fractionation; furthermore, delineation of the cavity can be challenging. Lately, low-energy X-ray intraoperative radiation therapy (IORT) applied to the resection bed has emerged in clinical practice, offering local ablative treatment with steep dose gradients towards the surrounding healthy brain. We here retrospectively describe 18 patients with resected brain metastases, which had undergone IORT, demonstrating the effectiveness and safety of this technique in accordance with previous studies. Background: Resection followed by local radiation therapy (RT) is the standard of care for symptomatic brain metastases. However, the optimal technique, fractionation scheme and dose are still being debated. Lately, low-energy X-ray intraoperative RT (lex-IORT) has been of increasing interest. Method: Eighteen consecutive patients undergoing BM resection followed by immediate lex-IORT with 16-30 Gy applied to the spherical applicator were retrospectively analyzed. Demographic, RT-specific, radiographic and clinical data were reviewed to evaluate the effectiveness and safety of IORT for BM. Descriptive statistics and Kaplan-Meyer analysis were applied. Results: The mean follow-up time was 10.8 months (range, 0-39 months). The estimated local control (LC), distant brain control (DBC) and overall survival (OS) at 12 months post IORT were 92.9% (95%-CI 79.3-100%), 71.4% (95%-CI 50.2-92.6%) and 58.0% (95%-CI 34.1-81.9%), respectively. Two patients developed radiation necrosis (11.1%) and wound infection (CTCAE grade III); both had additional adjuvant treatment after IORT. For five patients (27.8%), the time to the start or continuation of systemic treatment was <= 15 days and hence shorter than wound healing and adjuvant RT would have required. Conclusion: In accordance with previous series, this study demonstrates the effectiveness and safety of IORT in the management of brain metastases despite the small cohort and the retrospective characteristic of this analysis.