P. A. Blumenfeld, J. Feldman, E. Wajnryt, Y. Hillman, M. R. Wygoda, and A. Popovtzer; Hadassah Medical Center, Jerusalem 91120, Israel
Purpose/Objective(s): Re-irradiation is critical in managing recurrent malignancies in the head and neck and brain, despite the associated side effects. Proton bream radiation therapy (PBRT) with its distinct dosimetric advantages, offers a promising alternative. This study investigates the feasibility and safety of a novel fixed beam solution for PBRT, utilizing an image-guided robotic patient positioning system, the first available in Israel. Materials/
Methods: Patients with locally advanced recurrent head and neck (HN) and brain malignancies, previously irradiated, ECOG PS 0-2 considered for reirradiation, were eligible. Patients underwent CT simulation for photon IMRT and upright CT simulation for PBRT. Treatment plans were compared and patients with improved dosimetric benefit with PBRT were enrolled. We report dosimetric and acute toxicity outcomes. Results: 23 patients were eligible, of which 13 recurrent HN and 3 recurrent brain were enrolled. For all 16 patients, PBRT plans were superior in terms of relevant Organs At Risk. IMRT plans had a greater median maximum brainstem (19.8 vs. 2.8Gy (RBE), P<0.001), maximum spinal cord (17.8 vs. 13.8Gy, P<0.02), mean oral cavity (18.5 vs. 5.6Gy, P<0.001), mean contralateral parotid (6.2 vs. 0.2Gy, P<0.001), and mean constrictor muscles (23.8 vs. 14.1Gy, P<0.01) dose when compared to PBRT. 4 of 16 patients experienced acute grade 3 toxicity (mucositis, dysphagia, oral pain). There were no grade 4 or grade 5 toxicities in the entire cohort. Conclusion: Preliminary results demonstrate feasibility and dosimetric advantages of PBRT and low acute-toxicity using a chair-based fixed beam delivery system for recurrent head and neck and brain malignancies.
