Purpose: To determine the optimal dose-volume constraint for laryngeal sparing using three commonly employed intensity modulated radiation therapy (IMRT) approaches in patients with oropharyngeal cancer treated to the bilateral neck. Materials and methods: Thirty patients with stage II-IVA oropharynx cancers received definitive radiotherapy with split-field IMRT (SF-IMRT) to the bilateral neck between 2008 and 2013. Each case was re-planned using whole-field IMRT (WF-IMRT) and volumetric modulated arc therapy (VMAT) and plan quality metrics and dose to laryngeal structures was evaluated. Two larynx volumes were defined and compared on the current study: the Radiation Therapy Oncology Group (RTOG) larynx as defined per the RTOG 1016 protocol and the MDACC larynx defined as the components of the larynx bounded by the superior and inferior extent of the thyroid cartilage. Results: Target coverage, conformity, and heterogeneity indices were similar in all techniques. The RTOG larynx mean dose was lower with WF-IMRT than SF-IMRT (22.1 vs 25.8 Gy; P < 0.01). The MDACC larynx mean dose was 17.5 Gy ± 5.4 Gy with no differences between the 3 techniques. WF-IMRT and VMAT plans were associated with lower mean doses to the supraglottic larynx (42.1 vs 41.2 vs 54.8 Gy; P < 0.01) and esophagus (18.1 vs 18.2 vs 36 Gy; P < 0.01). Conclusions: Modern whole field techniques can provide effective laryngeal sparing in patients receiving radiotherapy to the bilateral neck for advanced oropharyngeal cancers. Summary: We evaluated laryngeal dose in patients with locally advanced oropharyngeal cancer treated to the bilateral neck using split-field IMRT (SF-IMRT), whole-field IMRT (WF-IMRT) and volumetric arc therapy (VMAT). All three techniques provided good sparing of laryngeal structures and were able to achieve a mean larynx dose < 33 Gy. There were no significant differences in dose to target structures or non-laryngeal organs at risk among techniques.
Bibliographical noteFunding Information:
Dr. Fuller receives academic‐industrial institutional grant funding from Elekta AB, and has received travel compensation from Elekta AB.
This research was supported in part by the Andrew Sabin Family Foundation; Dr. Fuller is a Sabin Family Foundation Fellow. Dr. Fuller receives funding and salary support from the National Institutes of Health (NIH), including: the National Institute of Biomedical Imaging and Bioengineering (NIBIB) Research Education Program award(1R25EB025787‐01); the National Institute for Dental and Craniofacial Research Award (1R01DE025248‐01/R56DE025248‐01); a National Science Foundation (NSF), Division of Mathematical Sciences, Joint NIH/NSF Initiative on Quantitative Approaches to Biomedical Big Data (QuBBD) Grant (NSF 1557679); the NIH Big Data to Knowledge (BD2K) Program of the National Cancer Institute (NCI) Early Stage Development of Technologies in Biomedical Computing, Informatics, and Big Data Science Award (1R01CA214825‐01); NCI Early Phase Clinical Trials in Imaging and Image‐Guided Interventions Program (1R01CA218148‐01); an NIH/NCI Cancer Center Support Grant (CCSG) Pilot Research Program Award from the UT MD Anderson CCSG Radiation Oncology and Cancer Imaging Program (P30CA016672) and an NIH/NCI Head and Neck Specialized Programs of Research Excellence (SPORE) Developmental Research Program Award (P50 CA097007‐10).