Is there a time interval after which you would not offer adjuvant radiotherapy for a malignant, grade 3 meningioma?

Adjuvant radiation for grade 3 meningioma is based on prior observational studies that generally reflect recurrence rates approaching 90% for grade III disease, and the insufficiency of salvage treatment approaches.

Given the small numbers of grade 3 tumors, and the heavy bias towards upfront postop ...