II can get SRS, too.

Top Line: Can SRS be considered for WHO grade II meningioma?

The Study: Here is an international multi-institutional retrospective cohort of 233 patients treated with SRS for WHO II meningioma. Almost all patients included in the study had upfront surgery with SRS reserved for gross residual disease or tumor recurrence. SRS dose was at physician discretion due to variable tumor size and location, but the most common Rx was 15 Gy x 1 via GammaKnife delivered at a median of one year from the most recent resection. The goal was to identify patients with favorable outcomes with SRS. Recursive partitioning analysis pointed to three major risk factors for recurrence: age >50, treatment volume >11.5 cc, and history of radiation and/or >1 previous resection. “Good risk” patients (n=137) with no more than one of the above risk factors and those with “bad risk” (n=96) had two or more risk factors. Progression-free survival at three years was significantly better for the good risk group (63%) than for the bad risk group (42%), and even overall survival was numerically better (98% and 88%, respectively). Ok, no huge surprise there, but is SRS an appropriate alternative to fractionated treatment? While this data can’t answer that question, the authors point to RTOG 0539 as an historic benchmark, where high-risk patients (i.e. WHO III, recurrent WHO grade II, or new WHO II subtotally resected) had a progression-free survival at 3 years of 59% after resection and adjuvant fractionated radiation. Compare that to 54% among the 218 patients in the current study who fit such criteria. And before you throw out that comparison due to a lack of WHO III tumors in the cohort, WHO III actually had better outcomes than recurrent WHO II in 0539. Finally, this series included only patients with gross disease.

TBL: Outcomes with SRS for WHO II meningiomas may be comparable to fractionated therapy, especially in good-risk patients (≤50, ≤1 prior resection, and no prior RT). | Kowalchuk, Int J Radiat Oncol Biol Phys 2021