Stereotactic radiosurgery for brain metastases: efficacy and toxicity

Abstract

Stereotactic radiosurgery (SRS) is increasingly being used as a treatment for brain metastases. Four research topics in the management of brain metastases in clinical practice have been chosen, with the unifying theme of investigating SRS efficacy and toxicity. The first topic is an investigation of patients who receive primary SRS (i.e., SRS of unresected metastases), but who die within six months of treatment. Possible causes for this are explored with the aim of proposing some new eligibility criteria for treatment. The role of SRS to the post-operative surgical cavity after complete resection of brain metastasis has been less widely studied than that of primary SRS. The second topic of investigation is the local control benefit of SRS to the post-operative surgical cavity, after complete resection of brain metastases, using the CyberKnife (CK) SRS platform and fractionated SRS. Conventional brain magnetic resonance imaging (MRI) is used to assess treatment response post-SRS, but it can be difficult to reliably differentiate tumour recurrence/progression from radiotherapy-related treatment-effects, also known as radionecrosis (RN). As the management of these processes are different, this makes subsequent clinical decision-making complex. The third topic of investigation is an evaluation of contrast clearance analysis MRI, also known as treatment response assessment maps (TRAMs), to differentiate recurrent/progressive tumour from RN. RN is an important late toxicity of SRS that can lead to neurological complications, and there is currently no gold-standard predictive biomarker. The fourth topic is an investigation of dose-volume metrics, to determine whether this can reliably estimate the likelihood of RN, in those who receive primary SRS.