Deep learning radiomics analysis for prediction of survival in patients with unresectable gastric cancer receiving immunotherapy

Objective: Immunotherapy has become an option for the first-line therapy of advanced gastric cancer (GC), with improved survival.Our study aimed to investigate unresectable GC from an imaging perspective combined with clinicopathological variables to identify patients who were most likely to benefit from immunotherapy.Method: Patients with unresectable GC who were consecutively treated with immunotherapy at two different medical centers of Chinese PLA General Hospital were included and divided into the training and validation cohorts, respectively.A deep learning neural network, using a multimodal ensemble approach based on CT imaging data before immunotherapy, was trained in the training cohort to predict survival, and an internal validation cohort was constructed to select the optimal ensemble model.Data from another cohort were used for external validation.The area under the receiver operating characteristic curve was analyzed to evaluate performance in predicting survival.Detailed clinicopathological data and peripheral blood prior to immunotherapy were collected for each patient.Univariate and multivariable logistic regression analysis of imaging models and clinicopathological variables was also applied to identify the independent predictors of survival.A nomogram based on multivariable logistic regression was constructed.Result: A total of 79 GC patients in the training cohort and 97 patients in the external validation cohort were enrolled in this study.A multi-model ensemble approach was applied to train a model to predict the 1-year survival of GC patients.Compared to individual models, the ensemble model showed improvement in performance metrics in both the internal and external validation cohorts.There was a significant difference in overall survival (OS) among patients with different imaging models based on the optimum cutoff score of 0.5 (HR = 0.20, 95 % CI: 0.10-0.37,P < 0.001).Multivariate Cox regression analysis revealed that the imaging models, PD-L1 expression, and lung immune prognostic index were independent prognostic factors for OS.We combined these variables and built a nomogram.The calibration curves showed that the C-index of the nomogram was 0.85 and 0.78 in the training and validation cohorts. Conclusion:The deep learning model in combination with several clinical factors showed predictive value for survival in patients with unresectable GC receiving immunotherapy.