Pre-treatment amide proton transfer imaging predicts treatment outcome in nasopharyngeal carcinoma

Objective To investigate the value of pre-treatment amide proton transfer-weighted (APTw) imaging for predicting survival of patients with nasopharyngeal carcinoma (NPC). Materials and methods Pre-treatment APTw imaging was performed in 77 NPC patients and the mean, 90th percentile, skewness, and kurtosis of APT asymmetry (APT(mean), APT(90), APT(skewness), and APT(kurtosis), respectively) were obtained from the primary tumor. Associations of APTw parameters with locoregional relapse-free survival (LRRFS), distant metastasis-free survival (DMFS), and disease-free survival (DFS) after 2 years were assessed by univariable Cox regression analysis and significant APTw parameters, together with age, sex, treatment, and stage as confounding variables, were added to the multivariable model. Kaplan-Meier analysis was used to determine the prognostic significance of patients with high or low APT values based on a threshold value from receiver operating characteristic curve analysis. Results Locoregional relapse, distant metastases, and disease relapse occurred in 14/77 (18%), 10/77 (13%), and 20/77 (26%) patients, respectively, at a median follow-up of 48.3 (10.6-67.4) months. Univariable analysis showed significant associations of LRRFS with APT(skewness)(HR = 1.98;p =0.034), DMFS with APT(mean)(HR = 2.44;p =0.033), and APT(90)(HR = 1.93;p =0.009), and DFS with APT(mean)(HR = 2.01;p =0.016), APT(90)(HR = 1.68;p =0.009), and APT(skewness)(HR = 1.85;p= 0.029). In multivariable analysis, the significant predictors for DMFS were APT(90)(HR = 3.51;p= 0.004) and nodal stage (HR = 5.95;p= 0.034) and for DFS were APT(90)(HR = 1.97;p= 0.010) and age (HR = 0.92;p= 0.014). An APT(90)>= 4.38% was associated with a significantly poorer DFS at 2 years than APT(90)< 4.38% (66% vs. 91%; HR = 4.01;p =0.005). Conclusion APTw imaging may potentially predict survival in patients with NPC. Key Points APTw imaging may provide new markers to predict survival in nasopharyngeal carcinoma. APT(90) is an independent predictor of distant metastases-free survival and disease-free survival. The APT(high) group is at higher risk of disease relapse than the APT(low) group.