Abstract
BACKGROUND AND PURPOSE: Radiation-induced changes can occur after stereotactic radiosurgery for brain AVMs, potentially causing symptomatic complications. We evaluated the incidence of such changes and the efficacy of repeat gamma knife radiosurgery for incompletely obliterated AVMs. MATERIALS AND METHODS: We retrospectively evaluated 150 patients who underwent gamma knife radiosurgery for AVMs between 2002 and 2020; twenty-five underwent further radiosurgical procedures for incompletely obliterated AVMs. We recorded the median margin doses at the first (median, 20 Gy; range, 12-23 Gy; AVM volume, 0.026-31.3 mL) and subsequent procedures (median, 18 Gy; range, 12-23 Gy; AVM volume, 0.048-9.2 mL). RESULTS: After the first treatment, radiologic radiation-induced changes developed in 48 (32%) patients, eight of whom had symptomatic changes. After repeat gamma knife radiosurgery, 16 of 25 patients achieved complete AVM obliteration (64%). The development of radiation-induced changes after the first treatment was significantly associated with successful obliteration by subsequent radiosurgery (OR = 24.0, 95% CI 1.20-483, P = .007). Radiation-induced changes occurred in only 5 (20%) patients who underwent a second gamma knife radiosurgery, one of whom experienced transient neurologic deficits. Between the first and repeat gamma knife radiosurgery procedures, there was no significant difference in radiologic and symptomatic radiation-induced changes (P = .35 and P = 1.0, respectively). CONCLUSIONS: Radiation-induced changes after the first gamma knife radiosurgery were associated with AVM obliteration after a repeat procedure. The risk of symptomatic radiation-induced changes did not increase with retreatment. When the first procedure fails to achieve complete AVM obliteration, a favorable outcome can be achieved by a repeat gamma knife radiosurgery, even if radiation-induced changes occur after the first treatment.