ESTRO 2024 - Abstract Book

S856

Clinical - CNS

ESTRO 2024

Results:

Clinical follow-up until euthanasia did not indicate radiotoxicity induced by MRT. During the first 3 months after MRT, quality of life (QoL) improved from 4/10 to 8.5/10. A considerable reduction of tumor-induced seizures was noted after the treatment; complete absence of seizures was reached from 2 weeks to 6 months post MRT. Convulsive seizures only reoccurred from 6 months on, induced by the tumor relapse. MRI revealed minimalization of the mass effect and normalization of the ventricular volume. At 1 month after the MRT exposure, the tumor volume reduced by 67.4% and by 87.4% at 3 months (see figure 1). Recurring tumor volume was only noted at 6 months post MRT (61.4% reduced tumor volume compared with the initial volume). The dog was euthanized 293 days post MRT (353 days post diagnosis) due to tumor-associated seizure activity and degrading well-being.

Conclusion:

This is the first neuro-oncologic veterinary trial of 3D-conformal synchrotron MRT for spontaneous intracranial tumors in large pet animals. Follow-up of 5 further pet dogs irradiated with 4 Gy cumulated MRT valley dose through 5 ports is currently ongoing. For comparison, 10 dogs have been treated at the hospital with conventional X-ray exposures and are currently monitored for tumor volume evolution, well-being and survival. Our study reveals that microbeam irradiation does not induce acute to late radiotoxicity in normal brain tissues and proves that MRT is a safe tool for brain tumor treatment in dogs. MRT improves quality of life and animal survival and leads to a remarkable tumor volume reduction despite relatively low valley dose delivery. The foreseen MRT valley dose escalation study is designed to further ameliorate the therapeutic ratio in canine patients. This trial is an essential last step towards the clinical transfer of MRT in the near future for the treatment of deep-seated human brain tumors.

Keywords: microbeam radiation therapy, canine brain tumor

References:

Adam JF, Balosso J, Bayat S, et al. Toward Neuro-Oncologic Clinical Trials of High-Dose-Rate Synchrotron Microbeam Radiation Therapy: First Treatment of a Spontaneous Canine Brain Tumor. Int. J. Radiat. Oncol. Biol. Phys. 2022;113:967 – 973.