Complications of stereotactic radiosurgery: Avoidable or inevitable?

Gamma knife radiosurgery (GKRS) is a popular radiosurgical tool for various benign and malignant intracranial pathologies. Our objective was to evaluate the spectrum of complications of GKRS, the timeline of adverse events, and the outcome following the radiosurgical intervention. We systematically searched for articles related to various complications using the following keywords: “Vascular complications”, “Gamma-knife”, “stereotactic”, “radiosurgery”, “complications”, “edema”, “vascular changes”, “malignancy”, and “alopecia”. The literature was separately evaluated for 'early ' (within 12 weeks of GKRS)' or 'delayed' (after 12 weeks of GKRS) sequalae. We separately evaluated the relevant animal studies for literature analysis, and for the histopathological changes that take place after radiosurgery. Following the systematic analysis, 543 articles were evaluated. With the predetermined criteria, we identified 36 studies detailing 72 cases. Vascular complications, radiosurgery induced malignancy, radiation necrosis and radiation induced edema were the major reported complications. A delayed hemorrhage after a latency period was the most common complication while administering GKRS for arteriovenous malformations. A repeat radiosurgical intervention was identified as the significant factor responsible for delayed hemorrhage. Post-radiosurgery intratumoral hemorrhage was observed in meningiomas, vestibular schwannomas, pituitary adenomas, pineocytomas and cerebellar astrocytomas. Following the administration of single fraction stereotactic radiosurgery (SRS) for brain metastases, necrosis was observed in 5.2% patients at 6 months, in 17.2% at 12 months, and in 34% patient population at 24 months. Delayed occlusive or proliferative vasculopathy, malignancy, necrosis and edema are rare, albeit probable, complications that occur after GKRS. There are no definite identifiable markers for determining the probability of developing these complications. The risks of radiosurgery-induced complications are more in patients with a history of prior radiation therapy, a large tumor volume, and the usage of non-conformal dose plans. The risk of radiation-induced tumour formation after a single-function radiosurgery is very low and should not be used as a reason to choose alternative treatment strategies for appropriate patients. The clinician should explain these probable risks to the patient before considering GKRS as a treatment option.