Predictors of radiation necrosis in long-term survivors after Gamma Knife stereotactic radiosurgery for brain metastases.
Background: The long-term risk of necrosis after radiosurgery for brain metastases is uncertain. We aimed to investigate incidence and predictors of radiation necrosis for individuals with more than 1 year of survival after radiosurgery for brain metastases.
Methods: Patients who had a diagnosis of brain metastases treated between December 2006 and December 2014, who had at least 1 year of survival after first radiosurgery were retrospectively reviewed. Survival was analyzed using the Kaplan-Meier estimator, and the incidence of radiation necrosis was estimated with death or surgical resection as competing risks. Patient and treatment factors associated with radiation necrosis were also analyzed.
Results: A total of 198 patients with 732 lesions were analyzed. Thirty-four lesions required salvage radiosurgery and 10 required salvage surgical resection. Median follow-up was 24 months. The estimated median survival for this population was 25.4 months. The estimated per-lesion incidence of radiation necrosis at 4 years was 6.8%. Medical or surgical therapy was required for 60% of necrosis events. Tumor volume and male sex were significant factors associated with radiation necrosis. The per-lesions incidence of necrosis for patients undergoing repeat radiosurgery was 33.3% at 4 years.
Conclusions: In this large series of patients undergoing radiosurgery for brain metastases, patients continued to be at risk for radiation necrosis throughout their first 4 years of survival. Repeat radiosurgery of recurrent lesions greatly exacerbates the risk of radiation necrosis, whereas treatment of larger target volumes increases the risk modestly.
Siddiqui ZA, Squires BS, Johnson MD, Baschnagel AM, Chen PY, Krauss DJ, Olson RE, Meyer KD, Grills IS. Predictors of radiation necrosis in long-term survivors after Gamma Knife stereotactic radiosurgery for brain metastases. Neurooncol Pract. 2020 Jul;7(4):400-408. doi: 10.1093/nop/npz067. Epub 2019 Dec 6. PMID: 32765891; PMCID: PMC7393283.