How would you advise a younger patient with residual/recurrent optic nerve meningioma, proceeding with radiotherapy, about the risks of malignant transformation or induction of other brain malignancies because of radiation?  

The risk of malignant transformation of an optic nerve sheath meningioma (ONSM) after RT appears to be remarkably low, much lower than the risk of blindness from an untreated, progressive ONSM. In a younger patient, I would lean toward RT for patients with imaging progression or early visual loss,...

A few caveats. For "younger patients," it is important to determine whether the tumor is in a setting of NF2, which is a significant fraction of these patients. The estimate of radiation-induced tumors will be higher in the NF2 subset than in the unaffected patients. Also, the expectations for tum...