Carbon-ions, protons or photons for head and neck cancer radiotherapy-an in silico planning study.

To compare dose to the organ at risk (OAR) and target coverage of carbon-ion beam, protons, and photons for patients with head and neck cancer. Treatment plans for carbon-ion pencil beam scanning (C-PBS) (64 Gy (RBE) in 16 fractions), proton pencil beam scanning (P-PBS), and volumetric modulated arc therapy (VMAT) (70 Gy in 35 fractions for P-PBS and VMAT) were generated and compared using different dose constraints per treatment modality. Dose metrics (e.g. D95,V20) were analyzed. Statistical significance was assessed by the Wilcoxon signed-rank test. Also, we investigated howmany normal tissues were irradiated above the constraint after achieving the planning goals (pass rate) in the OARs. C-PBS outperformed P-PBS and VMAT in PTV coverage (p = 0.01 for both); however, P-PBS and VMAT did not differ substantially from each another (p = 0.35). C-PBS was superior in limiting the dose to the OAR. The pass rates for C-PBS, P-PBS, and VMAT were 94%, 81%, and 69%, respectively. C-PBS demonstrated superior performance compared to VMAT and P-PBS in terms of dose conformation to the target volume and normal tissue sparing, and achieved the highest pass rate in meeting dose constraints.