Hypofractionated Stereotactic Radiation Therapy to the Resection Bed for Intracranial Metastases

Abstract

To retrospectively report the outcomes of a large multicenter cohort of patients treated with surgery and hypofractionated stereotactic radiation therapy (HFSRT) to the resection cavities of brain metastases (BMs). Between March 2008 and February 2015, 181 patients with no prior whole-brain radiation therapy (WBRT) were treated by HFSRT to the surgical bed of BM at the dose of 33Gy (3×11Gy). The primary endpoint was local control. Secondary endpoints were distant brain control, overall survival (OS), risk of radionecrosis, and leptomeningeal disease (LMD). Of the 189 resected lesions, 44% were metastatic from a non-small cell lung cancer primary tumor, and 76% of patients had a single BM at the time of treatment. With a median follow-up of 15months, the 6- and 12-month local control rates were 93% and 88%, respectively. On multivariate analysis, planning target volume (P=.005), graded prognostic assessment score (P=.021), and meningeal contact of BM (P=.032) were predictive of local failure. The 6- and 12-month distant brain control rates were 70% and 61%, respectively. Twenty-six patients (14%) developed signs of LMD at a median time of 3.8months. The preoperative tumor volume was predictive of LMD (P=.029). The median OS was 17months. The 6-, 12-, and 24-month OS rates were 79%, 62%, and 39%, respectively. Recursive partitioning analysis class 3 (P=.02), piecemeal resection (P=.017), and an increasing number of BMs (P<.01) were independent unfavorable prognostic factors for OS. Fifty-four patients (30%) were subsequently treated with salvage WBRT at a median time of 6.5months, and 41% were reirradiated with SRT. Radionecrosis occurred in 19% of cases at a median time of 15months and was associated with the infratentorial location of the BM (P=.0025). This study demonstrated the safety and efficacy of a 3×11Gy HFSRT regimen for the irradiation of BMs resection cavities. It was an alternative to adjuvant WBRT.