Focal cavity radiotherapy after neurosurgical resection of brain metastases: sparing neurotoxicity without compromising locoregional control

PURPOSE: Does focal cavity radiotherapy after resection of brain metastasis “spare” whole-brain radiotherapy, which is associated with toxicity for patients, through the complete course of their disease without compromising long-term local control of the brain? METHODS: We retrospectively analyzed outcomes of patients who underwent adjuvant focal cavity radiotherapy between 2014 and 2021 at our center. RESULTS: A total of 83 patients with 86 resected brain metastases were analyzed. 64% had singular, 36% two to four brain metastases. In cases with multiple metastases, omitted lesions were treated with radiosurgery. Median follow-up was 7.3 months (range 0–71.2 months), 1‑year overall survival rate was 57.8% (95% CI 44.9–68.8%). Radiotherapy was administered with a median biologically effective dose (α/β 10) surrounding the planning target volume of 48 Gy (range 23.4–60 Gy). Estimated 1‑year local control rate was 82.7% (95% CI 67.7–91.2%), estimated 1‑year distant brain control rate was 55.7% (95% CI 40.5–68.4%), estimated 1‑year leptomeningeal disease rate was 16.0% (95% CI 7.3–32.9%). Eleven distant brain recurrences could be salvaged with radiosurgery. In the further course of disease, 14 patients (17%) developed disseminated metastatic disease in the brain. Estimated 1‑year free of whole-brain radiotherapy rate was 72.3% (95% CI 57.1–82.9%). All applied treatments led to an estimated 1‑year neuro-control rate of 79.1% (95% CI 65.0–88.0%), estimated 1‑year radionecrosis rate was 23% (95% CI 12.4–40.5%). CONCLUSION: In our single-center study, focal cavity radiotherapy was associated with high local control. In three out of four patients, whole-brain radiotherapy could be avoided in the complete course of disease, using radiosurgery as salvage approach without compromising neuro-control.