Diagnostic performance of a deep-learning model using ¹⁸F-FDG PET/CT for evaluating recurrence after radiation therapy in patients with lung cancer

We developed a deep learning model for distinguishing radiation therapy (RT)-related changes and tumour recurrence in patients with lung cancer who underwent RT, and evaluated its performance.

We retrospectively recruited 308 patients with lung cancer with RT-related changes observed on ¹⁸F-fluorodeoxyglucose positron emission tomography–computed tomography (¹⁸F-FDG PET/CT) performed after RT. Patients were labelled as positive or negative for tumour recurrence through histologic diagnosis or clinical follow-up after ¹⁸F-FDG PET/CT. A two-dimensional (2D) slice-based convolutional neural network (CNN) model was created with a total of 3329 slices as input, and performance was evaluated with five independent test sets.

For the five independent test sets, the area under the curve (AUC) of the receiver operating characteristic curve, sensitivity, and specificity were in the range of 0.98–0.99, 95–98%, and 87–95%, respectively. The region determined by the model was confirmed as an actual recurred tumour through the explainable artificial intelligence (AI) using gradient-weighted class activation mapping (Grad-CAM).

The 2D slice-based CNN model using ¹⁸F-FDG PET imaging was able to distinguish well between RT-related changes and tumour recurrence in patients with lung cancer.