IMRT for Oropharyngeal Squamous Cell Carcinoma (OSCC): Analysis of Dosimetry and Patterns of Failure

Abstract

Materials/Methods: Data of 167 parotids of 87 patients from four Institutions were pooled; patients were treated with IMRT for different types of HNC with radical or adjuvant intent; 68/87 received 57.5–70 Gy in 30 fractions with a simultaneous integrated boost technique; 19/87 received 50.4–70.2 Gy in 28–39 fractions. Elective node chains received 50.4–54 Gy (1.8–2 Gy/fr). DV was evaluated by contouring parotids on CT images taken at the end and the start of RT (MVCT in two centers, n = 40; kVCT in two centers, n = 37). A number of parameters were recovered, including chemotherapy, surgery, primary tumor site, age, gender, total and daily dose, treatment duration (TD), weight variation (W), PTV(T) volume, initial parotid volume (IPV), parotid mean dose (Dmean), overlap between PTV(T+N) and parotid (OVP). Correlation between DVcc/% and these parameters was assessed through Kruskall-Wallis or Spearman tests. A stepwise logistic multivariate analysis (MVA, selecting variables with p value 0.1), was performed by considering as an endpoint a DVcc/% larger than the median value. Linear models of DV (continuous variable) based on the most predictive variables at MVA were finally developed.