Early-Delayed Radiotoxicity Associated With Stereotactic Radiation Therapy Following a Daily 6 Gy × 5 (30 Gy)...

Early-delayed side effects (EDSEs) following treatment of canine intracranial meningiomas with 1-3-fraction stereotactic radiation therapy (SRT) can cause worsening neurologic signs, and one potential method of mitigating this toxicity is reducing the dose per fraction. Twenty dogs with imaging-diagnosed intracranial meningiomas and telephone follow-up of at least 6 months received a protocol of 6 Gy × 5, daily (30 Gy). A 'possible EDSE' was defined as mental dullness, neurologic exacerbation of existing neurologic signs or new neurologic signs occurring within 1-4 months of completing SRT, regardless of the response to steroids and even if an MRI was not performed. A 'probable EDSE' was defined as mental dullness, neurologic exacerbation of existing neurologic signs or new neurologic signs occurring within 1-4 months of completing SRT. These signs were either reversible with the initiation or increased doses of prednisolone, or follow-up MRI revealed no evidence of an alternate explanation. No dogs experienced acute radiotoxicity or clinical signs compatible with EDSEs. The protocol appears to result in limited acute radiotoxicity, and further evaluation of the frequency of long-term toxicities and relative efficacy should be undertaken.