Repeated stereotactic radiosurgery (SRS) using a non-coplanar mono-isocenter (HyperArc™) technique versus upfront whole-brain radiotherapy (WBRT): a matched-pair analysis

Stereotactic radiosurgery (SRS) is an effective treatment option for multiple brain metastases (BMs). Modern mono-isocentric techniques allow the delivery of multiple stereotactic courses, in the event of intracranial failure. Nevertheless, limited data on effectiveness and toxicity have been reported in comparison to WBRT. Aim of this retrospective matched-pair analysis was to compare patients affected by limited BMs treated with multiple SRS courses using a mono-isocentric, non-coplanar technique (HyperArc (TM), Varian Medical System) to upfront WBRT. One hundred and two patients accounting for 677 BMs were treated with HyperArc (TM). In case of further intracranial progression, 44 treatment courses of 201 metastases in 19 patients, were treated by subsequent HyperArc (TM) courses. This population was matched with 38 patients treated with WBRT. The median BMs number was 4 (range 2-10) for HyperArc (TM) and 5 (range 2-10) for WBRT. Overall survival (OS) and toxicity were evaluated. The median follow-up was 9 months (range 3-40 months). The median OS was not reached (range 5-22 months) for HyperArc (TM) patients and 8 months (range 3-40 months) for WBRT patients, while the 1-year OS was 77% and 34.6% for HyperArc (TM) and WBRT, respectively (p = 0.001; HR 4.77, 95% CI 1.62-14.00). There was one case of radionecrosis. HyperArc (TM) is an effective and safe technique for the treatment of multiple BMs. In selected cases of intracranial oligorecurrence, further subsequent courses can be safely delivered with the same technical approach. Moreover, in patients with a limited number of BMs, SRS showed an improved survival outcome when compared to WBRT.