Intraoperative radiotherapy with low-energy x-rays after neurosurgical resection of brain metastases—an Augsburg University Medical Center experience

Abstract

Purpose External-beam radiotherapy (EBRT) is the predominant method for localized brain radiotherapy (LBRT) after resection of brain metastases (BM). Intraoperative radiotherapy (IORT) with 50-kV x‑rays is an alternative way to focally irradiate the resection cavity after BM surgery, with the option of shortening the overall treatment time and limiting normal tissue irradiation. Methods We retrospectively analyzed the outcomes of all patients who underwent neurosurgical resection of BM and 50-kV x‑ray IORT between 2013 and 2020 at Augsburg University Medical Center. Results We identified 40 patients with 44 resected BM treated with 50-kV x‑ray IORT. Median diameter of the resected metastases was 2.8 cm (range 1.5–5.9 cm). Median applied dose was 20 Gy. All patients received standardized follow-up (FU) including 3‑monthly MRI of the brain. Mean FU was 14.4 months, with a median MRI FU for alive patients of 12.2 months. Median overall survival (OS) of all treated patients was 26.4 months (estimated 1‑year OS 61.6%). The observed local control (LC) rate of the resection cavity was 88.6% (estimated 1‑year LC 84.3%). Distant brain control (DC) was 47.5% (estimated 1‑year DC 33.5%). Only 25% of all patients needed WBI in the further course of disease. The observed radionecrosis rate was 2.5%. Conclusion IORT with 50-kV x‑rays is a safe and appealing way to apply LBRT after neurosurgical resection of BM, with low toxicity and excellent LC. Close MRI FU is paramount to detect distant brain failure (DBF) early.

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

“…The estimated 1-year LC, DBC and OS were 84.3%, 33.5% and 61.6%, respectively. RN was observed in one patient and four patients developed LMD over the course the disease [30]. Based on these studies, Lex-IORT seems to be effective and safe regarding LC and RN rates, comparable to historical hFSRT data.…”

“…Therefore, low-energy X-ray intraoperative RT (lex-IORT) is gaining attention: surgical resection and RT performed within one procedure seems to be convenient regarding the duration of total treatment; at the same time, challenges of optimal target delineation for postsurgical cavities for external beam radiation therapy (EBRT) can be resolved [28]. Several studies have demonstrated effectiveness and safety with good local control rates up to 88% at 12 months [29][30][31]. This study is a retrospective descriptive single center analysis with a report of the first experience with lex-IORT for the management of BM at the Technical University of Munich (TUM) Medical Center in Munich, Germany (School of Medicine).…”

Management Strategies for Large Brain Metastases

“…LMD occurred in 3% of patients, and RN occurred in 7% of patients. Kahl et al reported their cohort of 40 patients with 44 resected metastases, who were treated with LEX-IORT using a median dose of 20Gy (66). Median overall survival was 26.4 months (1year survival of 61.6%), and the local control was 88.6% (1-year local control of 84.3%).…”

Soft-tissue simulation of the breast for intraoperative navigation and fusion of preoperative planning

“…Computational preoperative planning of surgical interventions entails multiple benefits, in particular reduced risk to the patient and shorter interds, computational preoperative planning has seen success in applications such as radiotherapy Calvo et al (2014) , neurosurgery Prada et al (2014) ; Kahl et al (2021) ; Nemoto et al (2002) , or orthognathic surgery Alcañiz et al (2021) .…”

“…IORT delivers a large dose of ionizing radiation to the tumor bed during surgery, thus maximizing the dose applied to the tumor while minimizing the dose applied to nearby healthy tissue. Preoperative planning of IORT involves calculation of a cumulative dose on a volume image that faithfully represents the patient’s anatomy, and is successfully used in, e.g., neurosurgery Prada et al (2014) ; Kahl et al (2021) ; Nemoto et al (2002) . However, to date IORT is hardly possible on breast cancer surgery, due to the strong mismatch between preoperative and intraoperative settings.…”