CANDIDATE DOSIMETRIC PREDICTORS OF LONG-TERM SWALLOWING DYSFUNCTION AFTER OROPHARYNGEAL INTENSITY-MODULATED RADIOTHERAPY

Purpose To investigate long-term swallowing function in oropharyngeal cancer patients treated with intensity modulated radiotherapy (IMRT), and to identify novel dose-limiting criteria predictive for dysphagia Methods and Materials Thirty-one patients with Stage IV oropharyngeal squamous carcinoma enrolled on a Phase 11 trial were prospectively evaluated by modified barium swallow studies at baseline, and 6, 12, and 24 months post-IMRT treatment Candidate dysphagia-associated organs at risk were retrospectively contoured into original treatment plans Twenty one (68%) cases were base of tongue and 10 (32%) were tonsil Stage distribution was T1 (12 patients), T2 (10), T3 (4), T4 (2), and TX (3), and N2 (24), N3 (5), and NX (2) Median age was 52 8 years (range, 42-78 years) Thirteen patients (42%) received concurrent chemotherapy during IMRT Thirteen (42%) were former smokers Mean dose to glottic larynx for the cohort was limited to 18 Gy (range, 6-39 Gy) by matching IMRT to conventional low-neck fields Results Dose-volume constraints (V30 < 65% and V35 < 35% for anterior oral cavity and V55 < 80% and V65 < 30% for high superior pharyngeal constrictors) predictive for objective swallowing dysfunction were identified by univariate and multivariate analyses Aspiration and feeding tube dependence were observed in only 1 patient at 24 months Conclusions In the context of glottic laryngeal shielding, we describe candidate oral cavity and superior pharyngeal constrictor organs at risk and dose-volume constraints associated with preserved long-term swallowing function, these constraints are currently undergoing prospective validation Strict protection of the glottic larynx via beam-split IMRT techniques promises to make chronic aspiration an uncommon outcome (C) 2010 Elsevier Inc