Abstract
PURPOSE: Although the apparent diffusion coefficient (ADC) value from diffusion-weighted imaging can provide insights into various pathological processes, no studies have examined the relationship between the pre-concurrent chemoradiotherapy (CCRT) mean ADC (ADC(mean)) values of the masseter muscles and radiation-induced trismus (RIT) in locally advanced nasopharyngeal carcinoma (LA-NPC) patients. Therefore, the current research aimed to investigate the significance of pre-CCRT masseter muscle ADC(mean) values for predicting the RIT rates in LA-NPC patients treated with definitive CCRT. MATERIALS AND METHODS: The pre-CCRT ADC(mean) values of the masseter muscles and the post-CCRT RIT rates were evaluated. A receiver operating characteristic curve analysis was employed to determine the optimal ADC(mean) cutoff. The primary objective was to examine the relationship between the pre-CCRT masseter muscle ADC(mean) values and the post-CCRT RIT rates. RESULTS: Seventy-seven patients were included. The optimal ADC(mean) cutoff value was 1381.30 × 10(-6) mm(2)/s, which divided the patients into two groups: an ADC(mean) < 1381.30 × 10(-6) mm(2)/s (n = 49) versus an ADC(mean) > 1381.30 × 10(-6) mm(2)/s (n = 28). A masseter muscle ADC(mean) > 1381.30 × 10(-6) mm(2)/s was found to be associated with significantly higher RIT rates than an ADC(mean) < 1381.30 × 10(-6) mm(2)/s (71.42% vs. 6.12%; p < 0.001). The multivariate analysis results confirmed a pre-CCRT masseter muscle ADC(mean) > 1381.30 × 10(-6) mm(2)/s as an independent predictor of RIT. CONCLUSIONS: Our study presents the first evidence establishing a connection between elevated masseter muscle ADC(mean) values and higher RIT rates in LA-NPC patients following CCRT. If confirmed with further research, these findings may help to categorize the risk of RIT in these patients.