Outcomes of adjuvant whole-brain radiotherapy versus hypofractionated stereotactic radiotherapy after surgical resection of brain metastases: a propensity score-matched analysis

Background: To assess the risks of local and distant failure and overall survival time in patients treated with hypofractionated stereotactic radiotherapy (HFSRT) to the postoperative cavity for brain metastases (BMs) compared with patients treated with adjuvant whole-brain radiation therapy (WBRT). Methods: Between July 2005 and February 2015, 196 non-randomized patients with 202 resected BMs were treated with post-operative WBRT or HFSRT at a single institution. The propensity score was included as a covariate to compare the interval to local failure, distant brain failure and overall survival time. The matching covariates consisted of the age, Karnofsky performance status, primary disease, number of BMs, extracranial disease status and presence or absence of extracranial metastases. Results: In total, 110 patients (54.5%) received adjuvant WBRT, and 92 HFSRT procedures (45.5%) were delivered after surgery. A Cox model adjusted on the propensity score showed that the brain distant failure was significantly associated with treatment modality. Compared with WBRT, the patients who received HFSRT had a significantly greater risk of developing distant brain recurrence [HR =3.37 (2.13-5.33), P<0.001]. No difference was observed in local failure (HR =1.16, P=0.77) between the groups. In the propensity-matched cohort, the effect of treatment on survival was not significant (P=0.14), but it depended on the time. Within the first 20 months, the patients treated with WBRT had a 2 times higher risk of death than did patients treated with HFSRT [HR =2.17 (1.42-3.32), P=0.0003]. Conclusions: Compared with the standard WBRT after the resection of BMs, stereotactic radiotherapy to the surgical bed produced a comparable local control rate to that of WBRT with a survival advantage in the first 20 months.