Post-operative Stereotactic Radiosurgery to Brain Metastases Cavity: A Large, Observational Single-Centre Series From the United Kingdom.

Introduction Stereotactic radiosurgery (SRS) is widely regarded as the standard of care after the resection of brain metastases in order to reduce local cavity recurrence risk. The objective of this study was to explore the reproducibility of published outcomes for patients receiving post-operative stereotactic radiosurgery (cavity SRS) in a National Health Service (NHS) setting for a non-selective series of patients. For our service, the median interval between surgery to cavity SRS (cSRS) is eight weeks, whereas similar timelines have been found to have a deleterious impact on survival in the published literature. Materials and methods This retrospective cohort study analysed outcomes for 100 consecutive cSRS patients treated between 2015 and 2019 at a Northern English cancer centre. A case note review was conducted, with collection of primary tumour, disease extent, SRS treatment details and outcome data. Results Median survival for all primaries was 16 months, with renal, melanoma and breast having optimum survival at 28, 26 and 17 months, respectively. Local relapse was seen in 6/100 patients, with a further 6/100 patients having leptomeningeal disease. Radionecrosis was rare (3/100). Dose prescription, size of PTV and number of metastatic sites did not produce a statistically significant impact on survival times. The detrimental impact of delay from surgery to SRS beyond 56 days reported by others was not evident in our series (p-value 0.786). Conclusion SRS to the surgical cavity after the resection of brain metastases in eligible patients produces favourable outcomes and demonstrates outcomes comparable to the world literature. Our study does not demonstrate a significant drop in survival with delay beyond eight weeks to cSRS, which may reflect a different cause of delay in our NHS setting than in other healthcare systems.