Diagnosis of thyroid cancer using deep convolutional neural network models applied to sonographic images: a retrospective, multicohort, diagnostic study

Background The incidence of thyroid cancer is rising steadily because of overdiagnosis and overtreatment conferred by widespread use of sensitive imaging techniques for screening. This overall incidence growth is especially driven by increased diagnosis of indolent and well-differentiated papillary subtype and early-stage thyroid cancer, whereas the incidence of advanced-stage thyroid cancer has increased marginally. Thyroid ultrasound is frequently used to diagnose thyroid cancer. The aim of this study was to use deep convolutional neural network (DCNN) models to improve the diagnostic accuracy of thyroid cancer by analysing sonographic imaging data from clinical ultrasounds. Methods We did a retrospective, multicohort, diagnostic study using ultrasound images sets from three hospitals in China. We developed and trained the DCNN model on the training set, 131 731 ultrasound images from 17 627 patients with thyroid cancer and 180 668 images from 25 325 controls from the thyroid imaging database at Tianjin Cancer Hospital. Clinical diagnosis of the training set was made by 16 radiologists from Tianjin Cancer Hospital. Images from anatomical sites that were judged as not having cancer were excluded from the training set and only individuals with suspected thyroid cancer underwent pathological examination to confirm diagnosis. The model's diagnostic performance was validated in an internal validation set from Tianjin Cancer Hospital (8606 images from 1118 patients) and two external datasets in China (the Integrated Traditional Chinese and Western Medicine Hospital, Jilin, 741 images from 154 patients; and the Weihai Municipal Hospital, Shandong, 11 039 images from 1420 patients). All individuals with suspected thyroid cancer after clinical examination in the validation sets had pathological examination. We also compared the specificity and sensitivity of the DCNN model with the performance of six skilled thyroid ultrasound radiologists on the three validation sets. Findings Between Jan 1, 2012, and March 28, 2018, ultrasound images for the four study cohorts were obtained. The model achieved high performance in identifying thyroid cancer patients in the validation sets tested, with area under the curve values of 0.947 (95% CI 0.935-0.959) for the Tianjin internal validation set, 0.912 (95% CI 0.865-0.958) for the Jilin external validation set, and 0.908 (95% CI 0.891-0.925) for the Weihai external validation set. The DCNN model also showed improved performance in identifying thyroid cancer patients versus skilled radiologists. For the Tianjin internal validation set, sensitivity was 93.4% (95% CI 89.6-96.1) versus 96.9% (93.9-98.6; p=0.003) and specificity was 86.1% (81.1-90.2) versus 59.4% (53.0-65.6; p< 0.0001). For the Jilin external validation set, sensitivity was 84.3% (95% CI 73.6-91.9) versus 92.9% (84.1-97.6; p=0.048) and specificity was 86.9% (95% CI 77.8-93.3) versus 57.1% (45.9-67.9; p< 0.0001). For the Weihai external validation set, sensitivity was 84.7% (95% CI 77.0-90.7) versus 89.0% (81.9-94.0; p=0.25) and specificity was 87.8% (95% CI 81.6-92.5) versus 68.6% (60.7-75.8; p< 0.0001). Interpretation The DCNN model showed similar sensitivity and improved specificity in identifying patients with thyroid cancer compared with a group of skilled radiologists. The improved technical performance of the DCNN model warrants further investigation as part of randomised clinical trials. Copyright (C) 2018 Elsevier Ltd. All rights reserved.