Stereotactic Radiosurgery for Large Benign Intracranial Tumors

Historically, it is stated that large intracranial tumors, herein defined as a maximum dimension of ≥3 cm or tumor volume ≥14.2 cm³, are not candidates for stereotactic radiosurgery (SRS). We report outcomes of patients with large benign intracranial tumors treated with SRS.

With institutional review board approval, we retrospectively identified 74 patients with large benign intracranial tumors (59 meningiomas, 9 vestibular schwannomas, and 6 glomus jugulare tumors) treated with robotic SRS (2007-2018). Patients received definitive SRS in 47.3% of the cases, adjuvant to surgical resection in 44.6%, and salvage after past radiation treatment in 8.1%. A median tumor volume of 16.0 cm³ (range, 10.1-65.5 cm³) received a median dose of 24.0 Gy (range, 14.0-30.0 Gy) in a median of 3 fractions (range, 1-5), for a median single fraction equivalent dose (with alpha/beta of 3) of 14.8 Gy (range, 11.3-18.0 Gy). The Kaplan-Meier estimate of tumor local control (LC) was calculated from date of SRS.

With a median clinical follow-up of 32.8 months (range, 0.6-125.9 months) and median radiologic follow-up of 28.5 months (range, 0.6-121.4 months), LC was 96.5% (95% confidence interval, 92.4%-100%) at 3 years and 91.7% (95% confidence interval, 87.6%-95.7%) at 5 years. Adverse radiation effect (ARE) was seen in 10 patients (13.5%) at a median of 13.5 months (range, 7.8-34.5 months). ARE occurred in 9% of those with prior treatment compared with 5% who were radiation-naïve (P = 0.23). With 236.4 person-years of follow-up, no secondary malignancies were seen.

Despite the historical adage, we find that SRS provides high rates of LC for these large tumors, with rates of ARE similar to historical reports of SRS for smaller benign tumors.