Background Carbon ion radiotherapy (CIRT) yields biophysical advantages compared to photons but randomized studies for the reirradiation setting are pending. The aim of the current project was to evaluate potential clinical benefits and drawbacks of CIRT compared to volumetric modulated arc therapy (VMAT) in recurrent head and neck cancer. Methods Dose-volume parameters and local failure patterns of CIRT compared to VMAT were evaluate in 16 patients from the randomized CARE trial on head and neck cancer reirradiation. Results Despite an increased target dose, CIRT resulted in significantly reduced organ at risk (OAR) dose across all patients (− 8.7% Dmean). The dose-volume benefits were most pronounced in the brainstem (− 20.7% Dmax) and the optic chiasma (− 13.0% Dmax). The most frequent local failure was type E (extraneous; 50%), followed type B (peripheral; 33%) and type A (central; 17%). In one patient with type A biological and/or dosimetric failure after CIRT, mMKM dose recalculation revealed reduced target coverage. Conclusions CIRT resulted in highly improved critical OAR sparing compared to VMAT across all head and neck cancer reirradiation scenarios despite an increased prescription dose. Local failure pattern analysis revealed further potential CIRT specific clinical benefits and potential pitfalls with regard to image-guidance and biological dose-optimization.

Background Due to the increasing expertise in transoral laser surgery and image-guided radiation therapy, treatment outcomes have recently improved in patients with early-stage glottic cancer. The objective of the current study was to evaluate intensity-modulated proton therapy (IMPT) as novel treatment option. Methods A total of 15 patients with T1-2N0 glottic squamous cell carcinoma, treated between 2017 and 2020, were evaluated. Toxicity was recorded according to the Common Terminology Criteria for Adverse Events (CTCAE) v4.03. Results The majority were T1a/b tumors (66.7%) and no patient had lymph node or distant metastases. The median total dose was 70 Gy relative biological effectiveness (RBE) (range 66–70 Gy RBE). The one- and two-year OS and metastases-free survival were 100%. One patient developed local failure and received salvage laryngectomy. No higher-grade acute or late toxicity was reported. The mean number of CTCAE grade I and II overall toxicity events per patient was 4.1 (95%-[confidence interval] CI 3.1–5.3) and 1.0 (95%-CI 0.5–1.5). Conclusion High-precision proton therapy of T1-2N0 glottic cancer resulted in exceptional treatment tolerability with high rates of laryngeal function preservation and promising oncological outcome. IMPT has the potential to become a standard treatment option for patients with early-stage laryngeal cancer.