SU‐E‐T‐274: Dosimetric Indicators of Radiation‐Induced Toxicity in Meningioma Patients

Purpose: In this study, we retrospectively reviewed treatment plans and normal tissue toxicities for patients who were treated for meningiomas to investigate the correlation between DVH parameters and late Grade 3 radiation‐induced brainstem toxicity and hearing or vision changes. Methods: We analyzed data from 26 patients treated for brain meningiomas with either proton radiation or photon IMRT (11 were treated to 54Gy and 15 to 59.4Gy or higher) between 2009 and 2012 at the University of Pennsylvania. Five patients developed late Grade 3 toxicity with the remaining patients having late Grade 2 toxicity or less. Eight patients experienced hearing changes and seventeen experienced vision changes. We evaluated the maximum brainstem dose and volume of brainstem receiving more than 50∼54Gy for late Grade 3 toxicities. We also evaluated maximum and mean doses to the optic structures and cochlea. Statistical significance of the correlation between late Grade 3 toxicity or hearing and vision changes and the above mentioned DVH constraints was evaluated using Fisher exact test (two‐tailed). Results: The proportion of patients with Dmax > 45Gy or Dmean > 30 Gy for the cochlea was significantly greater in patients with hearing changes (p < 0.05 and p < 0.1 respectively). While for the brainstem a difference in the proportion of patients with and without late Grade 3 toxicity and with V54Gy > 5% was observed, this difference did not reach statistical significance. Conclusion: Differences were observed in the DVHs of meningioma patients who experienced radiation injury after radiation therapy. The mean dose to the cochlea is related to the likelihood of developing hearing changes. Based on the results of this study, dose volume parameters (that is, V54Gy) for the brainstem may be expected to be associated with Grade 3 toxicity in a larger cohort of patients.