A systematic review of particle-based treatment modalities for adenoid cystic carcinomas of the head and neck.

Purpose: Determine efficacy (local control, overall survival, and toxicities) of particle-based therapy (fast neutron therapy (FNT), proton beam therapy (PBT), carbon ion radiotherapy (CIRT)) in the treatment of adenoid cystic carcinomas (ACCs) of the head and neck.

Methods: This systematic literature review was conducted with adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All published work on the treatment of ACCs through particle-based treatment modalities (FNT, PBT, CIRT) with adequate reporting of patient outcomes in the English language were considered eligible for this systematic review.

Results: 44 studies (6 FNT, 16 PBT, 12 CIRT, and 10 multiple particles) reporting on ACC patient outcomes following particle therapy were included in this review. There were 41 retrospective and 3 prospective studies. Each particle modality was split into 2 series to ensure equitable evaluation. The median local control (LC) and overall survival (OS) rates were as follows: FNT consecutive 5-year 57 % & 72 %, FNT independent 5-year 61 % & 89.4 %, PBT ACC 2-year 94 % & 5-year 76 %, PBT mixed histology 2-year 89 % & 3-year 77.7 %, CIRT ACC 5-year 68.6 % & 74 %, and CIRT mixed histology 5-year 68% & 59.7%. The most common toxicities across the modalities were mucositis, dermatitis, brain/bone necrosis, and visual/auditory abnormalities.

Conclusion: This literature review suggests that PBT and CIRT are the preferred RT modality for ACC treatment with excellent LC rates and acceptable toxicity profiles in the adjuvant and definitive setting.