Acute side effects of proton and photon radiotherapy for medulloblastoma: a retrospective national multicenter study.

PURPOSE: A comparison of acute toxicity between photon and proton radiotherapy (RT) for children undergoing treatment for medulloblastoma.

METHODS

This retrospective multi-institutional cohort study included 96 children < 18 years treated for medulloblastoma in Sweden during 2008-2020. Patients treated with protons (n = 37) and photons (n = 59) were compared regarding acute side effects and radiation dose to intracerebral organs at risk (OARs). Data was collected from a prospectively maintained national database and was supplemented from a retrospective review of medical records. Acute symptoms were graded according to CTCAE (Common Terminology Criteria for Adverse Events), maximum grade occurring during RT and within 2 months after RT. Hematological toxicity was evaluated according to maximum grade and percentual reduction during RT.

RESULTS

No significant differences in incidence or severity of acute symptoms were observed between proton-RT and photon-RT; grade ≥ 2 fatigue (5.4 vs. 10.2%), headache (2.7 vs. 3.4%), nausea (43.2 vs. 42.4%), dermatitis (5.4 vs. 15.3%), gastrointestinal toxicity (0 vs. 0%), weight loss (10.8 vs. 8.5%). Median percentual reduction (0% vs. -11,25%) in hemoglobin was significantly smaller during proton-RT (p < 0.001). No difference was observed for leucocytes, neutrophiles, or platelets. Absorbed mean dose to intracranial OARs was significantly lower with proton-RT.

CONCLUSION

This is one of the largest studies comparing acute side effects of proton-RT and photon-RT including only paediatric medulloblastoma patients. Proton-RT was safe and well tolerated regarding acute side effects. Absorbed dose to intracranial OARs was significantly lower with proton-RT. Further investigations of long-term side effects and cognitive evaluation is needed to show that this will translate into true clinical value for patients.