Deep learning in nasopharyngeal carcinoma: A retrospective cohort study of 3D convolutional neural networks on magnetic resonance imaging

Abstract

Background: We aimed to establish a prognostic model based on magnetic resonance imaging using deep learning to predict disease‐free survival in patients with non‐metastatic nasopharyngeal carcinoma. Methods: In this retrospective, cohort study, we included 1636 patients who were diagnosed with non‐metastatic nasopharyngeal carcinoma and underwent radical treatment at the Sun Yat‐sen University Cancer Center. Patients from October 2010 to March 2015 were randomly divided into training cohort (n=878) and validation cohort (n=376); 382 patients from April 2015 to September 2015 were separated as test cohort. 3D DenseNet models learned deep representations of pre‐treatment MRI and risk scores were extracted to predict PFS in the training cohort. We evaluated the accuracy of the prognostic model in validation and test cohorts. The primary endpoint was DFS, and the secondary endpoint was distant metastasis‐free survival (DMFS). Results: A series of risk scores for each patient were extracted from 3D DenseNet models, and an optimal cut‐off value of risk scores was generated to classify patients into low‐risk and high‐risk group in the training cohort. Patients with low‐risk scores had better DFS (hazard ratio [HR] 0.62, 95% CI 0.55 ‐0.70; p<0.0001) and DMFS (HR 0.62, 95% CI 0.48 ‐0.81; p<0.0003) than patients with low‐risk scores. And we validated the prognostic accuracy of risk scores in the validation and test cohorts. In addition, patients who received concurrent chemotherapy had a poorer DFS (hazard ratio [HR] 7.79, 95% CI 1.08 ‐56.00; p<0.041) compared with those who did not receive concurrent chemotherapy in low‐risk group, meanwhile, patients with or without concurrent chemotherapy had similar outcomes in the high‐risk group (HR 2.39, 95% CI 0.59 ‐9.62; p=0.22). We also developed a nomogram based on risk scores and several clinical factors that predicted an individual's risk of DFS. Conclusions: MRI‐based 3D DenseNet models are effective tools to learn deep representations and extract risk scores of DFS. Risk scores can be reliable prognostic factors to select which patients benefit from concurrent chemotherapy.