Predictors of PEG dependence after IMRT±chemotherapy for oropharyngeal cancer.

Abstract

To prospectively assess predictors of PEG dependence after IMRT with/without concomitant chemotherapy (CHT). One-hundred-seventy-one patients were considered (exclusive RT: 58, RT+CHT: 113; 159/171 treated at a median dose of 70 Gy, 2 Gy/fr). Patients treated with RT+CHT underwent prophylactic PEG insertion; PEG was as needed for the others. A number of clinical factors and dose-volume information concerning oral mucosa (OM), constrictors, masticatory muscles, larynx, esophagus and parotids were available. The 25th/10th percentiles of the duration of PEG dependence were our end-points (respectively 3.3 and 7 months, PEG3/PEG7). Logistic uni and multi-variate (MVA) analyses were performed. Concerning PEG3, the independent predictors at MVA were: CHT/PEG policy (OR: 6.8, p=0.001), V9.5G_OMGy/week (OR: 1.017, p=0.01), larynx V50 (OR: 1.018, p=0.01) and superior constrictor (SC) D_mean (OR: 1.002, p=0.005); the predictive value of the model (AUC) was 0.818 (95% CI: 0.751-0.873). The independent predictors of PEG7 were: larynx V50 (OR: 1.042, p=0.0005) and SC D_mean (OR: 1.003, p=0.02), symptoms at diagnosis (yes vs no, OR: 3.6, p=0.08) and sex (male vs female, OR: 0.25, p=0.07); AUC was 0.897 (95% CI: 0.841-0.939). OM V9.5 Gy/week and CHT/PEG_policy modulate the risk of early PEG dependence. For longer PEG dependence, larynx V50 (or D_mean) and SC D_mean are highly predictive, suggesting that the fibrosis of constrictors and larynx is the main cause.