Development and validation of a nomogram to predict pathological complete response in patients with locally advanced gastric adenocarcinoma treated with neoadjuvant chemotherapy in combination with PD-1 antibodies

Background: Currently, the survival benefits of combining neoadjuvant chemotherapy with programmed death 1 (PD-1) antibody immunotherapy in advanced gastric adenocarcinoma remain controversial. Emerging evidence suggests that the survival benefits of neoadjuvant therapy in advanced gastric adenocarcinoma hinge upon the attainment of pathological complete response (pCR). Therefore, the prediction of pCR in patients undergoing neoadjuvant chemotherapy combined with PD-1 antibody immunotherapy holds significant importance and is beneficial for the individualized treatment of gastric cancer (GC) patients. Methods: Clinical and pathological characteristics of patients with GC who received neoadjuvant chemotherapy combined with PD-1 inhibitor (camrelizumab) therapy and radical gastrectomy between January 2019 and December 2020 at the Affiliated Cancer Hospital of Zhengzhou University & Henan Cancer Hospital were retrospectively analyzed. A total of 52 patients were enrolled in the study, with all subjects assigned to the training set. The neoadjuvant regimen consisted of a combination of PD-1 inhibitor and fluorouracil analogues plus oxaliplatin, comprising two drugs. The patients were divided into a pCR group and a non-pCR group according to pCR occurrence. Multifactor logistic regression analysis was applied to determine the correlation between each factor and pCR. A prediction model was developed based on the results of the logistic regression analysis. The predictive performance of the model was evaluated using the receiver operating characteristic curves. Internal verification was completed via the bootstrapping method. Results: The pCR was observed in 10 out of 52 patients (19.2%). The results of binary logistic regression multivariate analysis showed that cN stage [odds ratio (OR): 0.215; P=0.03], combined positive score (CPS) (OR: 6.364; P=0.026), and tumor diameter (OR: 0.112; P=0.026) were independent predictors of pCR. The nomogram prediction model for the pCR was plotted with a concordance index of 0.923 [95% confidence interval (CI): 0.8441-1]. Conclusions: Neoadjuvant chemotherapy combined with PD-1 antibodies may be the preferred option for patients with advanced gastric adenocarcinoma who have a small tumor diameter, no or few lymph node metastases, and high CPS. The presented nomogram model exhibits the potential to predict pCR in advanced gastric adenocarcinoma patients, showcasing satisfactory predictive performance and potentially facilitating the implementation of personalized treatment strategies.