Postoperative local fractionated radiotherapy for resected single brain metastases.

PURPOSE: Evaluation of postoperative fractionated local 3D-conformal radiotherapy (3DRT) of the resection cavity in brain metastases. PATIENTS AND METHODS: Between 2011 and 2016, 57 patients underwent resection of a single, previously untreated (37/57, 65%) or recurrent (20/57, 35%) brain metastasis (median maximal diameter 3.5 cm [1.1-6.5 cm]) followed by 3DRT. For definition of the gross tumor volume (GTV), the resection cavity was used and for the clinical target volume (CTV), margins of 1.0-1.5 cm were added. Median dose was 48.0 Gy (30.0-50.4 Gy) in 25 (10-28) fractions; most patients had 36.0-42.0 Gy in 3.0 Gy fractions (n = 16, EQD210Gy 39.0-45.5 Gy) or 40.0-50.4 Gy in 1.8-2.0 Gy fractions (n = 37, EQD210Gy 39.3-50.0 Gy).
RESULTS: Median follow-up was 18 months. Local control rates were 83% at 1 year and 78% at 2 years and were significantly influenced by histology (breast cancer 100%, non-small lung cancer 87%, melanoma 80%, colorectal cancer 26% at 2 years, p = 0.006) and resection status (p < 0.0001), but not by EQD210Gy or size of the planning target volume (median 96.7 ml [16.7-282.8 ml]). At 1 and 2 years, 74% and 52% of the patients were free from distant brain metastases. Salvage procedures were applied in 25/27 (93%) of recurrent patients. Survival was 68% at 1 year and 41% at 2 years and was significantly improved in younger patients (p = 0.006) with higher Karnofsky performance score (p < 0.0001) and without prior radiotherapy (54% vs. 9% at 2 years, p = 0.006). No cases of radiographic or symptomatic radionecrosis were observed.
CONCLUSION: Adjuvant fractionated local 3DRT is highly effective in radiosensitive, completely resected metastases and should be considered for treating large resection cavities as an alternative to postoperative stereotactic single dose or hypofractionated radiosurgery.