Top Line: What are the outcomes of hypofractionated stereotactic radiotherapy (SRT) for primary treatment of large or critically-located, grade I meningiomas?
The Study: Single fraction SRS is an effective treatment option for WHO grade I meningioma. However, for large tumors and those adjacent to critical structures, hypofractionated stereotactic radiotherapy (SRT) is often preferred to reduce the risk of toxicity. This single-arm, single-center, Italian phase 2 trial evaluated the safety and efficacy of SRT for large or critically-located meningiomas. Patients (n=166) had biopsy confirmed (49%) or presumed (51%) WHO grade I meningioma that were ≥3 cm and/or located within 3 mm of the optic nerves, optic chiasm, cavernous sinus, or brainstem. The majority (87%) had skull-base meningiomas, and 70% had neurological dysfunction with the most common being visual impairment (44%). Everyone was treated with 5 fraction SRT using CyberKnife. The target volume consisted of the contrast-enhancing GTV with no additional CTV or PTV margin. The prescription dose was prescribed to the 80% (+/-5%) isodose line so that 95% of the target received the prescribed dose. The median target volume was 10.5 cc. The majority (89%) received 25 Gy in 5 fractions while the rest received either 22.5 Gy or 20 Gy in 5 fractions. With a median follow up of 59 months, local control was 95% with 50% having a partial response and 45% stable disease. Baseline oculomotor dysfunction improved in 55%, visual deficits remained stable in 87%, and trigeminal pain/numbness was improved in 91%/13% of effected patients. The rate of any treatment-related toxicity was 12.7%, and the rate of toxicity among patients with a minimum 5 years follow up was 11.7%. There was no reported acute toxicity. The median time to a toxicity event was 10 months. Visual acuity deterioration (5%) and trigeminal sensory loss (4%) were the most frequent types of toxicity.
TBL: This prospective phase 2 trial shows a high rate of control (95%) and relatively low toxicity (12.7%) with hypofractionated SRT for large or critically-located meningiomas. | Pinzi, Int J Radiat Oncol Biol Phys 2022