A Risk Prediction Model by LASSO for Radiation-Induced Xerostomia in Patients With Nasopharyngeal Carcinoma Treated With Comprehensive Salivary Gland-Sparing Helical Tomotherapy Technique

Abstract

Objective: This study aimed to develop a least absolute shrinkage and selection operator (LASSO)-based multivariable normal tissue complication probability (NTCP) model to predict radiation-induced xerostomia in patients with nasopharyngeal carcinoma (NPC) treated with comprehensive salivary gland-sparing helical tomotherapy technique.

Methods and materials: LASSO with the extended bootstrapping technique was used to build multivariable NTCP models to predict factors of patient-reported xerostomia relieved by 50% and 80% compared with the level at the end of radiation therapy within 1 year and 2 years, R50-1year and R80-2years, in 203 patients with NPC. The model assessment was based on 10-fold cross-validation and the area under the receiver operating characteristic curve (AUC).

Results: The prediction model by LASSO with 10-fold cross-validation showed that radiation-induced xerostomia recovery could be predicted by prognostic factors of R50-1year (age, gender, T stage, UICC/AJCC stage, parotid Dmean, oral cavity Dmean, and treatment options) and R80-2years (age, gender, T stage, UICC/AJCC stage, oral cavity Dmean, N stage, and treatment options). These prediction models also demonstrated a good performance by the AUC.

Conclusion: The prediction models of R50-1year and R80-2years by LASSO with 10-fold cross-validation were recommended to validate the NTCP model before comprehensive salivary gland-sparing radiation therapy in patients with NPC.

Keywords: LASSO; helical tomotherapy technique; nasopharyngeal carcinoma; prediction model; xerostomia.

Figure 1

Delineation of target volume Red line: pGTVnx; brown line: pGTVnd; pink line: PTV1; dark green line: oral cavity; blue line: parotid gland; green line: submandibular gland.

Figure 2

Comparison of the mean dose (Dmean) of PG, SMG, and OC with different T (A) and N (B) stages.

Figure 3

LASSO coefficient profiles of the eleven R50-1year (A) and sixteen R80-2years (B) related events with non-zero coefficients determined by the optimal lambda.