COMBINATORIC: Carbon Ion Boost With Photons or Protons in Salivary Gland and Sinonasal Cancers

To evaluate the outcomes of combining carbon ion radiotherapy boost (CIRTb) with photons (Ph) or protons (PT) for locally advanced salivary gland and sinonasal cancers (SGCs and SNCs).

Sixty-nine patients with SGCs and SNCs received CIRTb to high-risk CTV and Ph or PT to low-risk CTV (LR-CTV) from October 2014 to September 2022. Two-year local relapse-free survival (LRFS) was analyzed with Kaplan-Meier. Toxicity according to Common Terminology Criteria for Adverse Events v5. Variables affecting toxicities were analyzed with chi-squared and Mann-Whitney U tests.

Patients received a median CIRTb dose of 15 Gy RBE, with 24 (35%) receiving Ph and 45 (65%) receiving PT. With a median follow-up of 1805 months, 2-year LRFS achieved 89% (95% CI: 81-98). Female (p = 0.045) reported better 2-year LRFS rates: 95% (95% CI: 87-100) versus 84% (95% CI: 72-98). Acute and late G2+ toxicity were, respectively, 80% and 60%. Ph (p = 0.004) and smaller LR-CTV (p = 0.004) reduced acute and late toxicities. No G4 late toxicity was reported.

CIRT combined with Ph or PT seems a valuable option for locally advanced SGCs and SNCs. Prospective studies are needed to select the best treatment combination.