Competing risk nomogram predicting initial loco-regional recurrence in gastric cancer patients after D2 gastrectomy

Background: Lacking quantitative evaluations of clinicopathological features and the risk factors for loco-regional recurrence (LRR) in gastric cancer after D2 gastrectomy, we aimed to develop a competing risk nomogram to identify the risk predictors for initial LRR. Methods: We retrospectively analysed 1105 patients who underwent radical gastrectomy with D2 resection for stage I-III gastric cancer. A nomogram predicting initial LRR of gastric cancer was conducted based on Fine and Grey's competing risk analysis. The predictive accuracy and discriminative ability of the model were determined using the concordance index (C-index) and calibration curve. Decision tree analysis was performed for patient grouping. Results: At a median follow-up of 28.4months, 274 patients developed 373 first recurrence events (local, regional, and distant disease). The median recurrence-free survival (RFS) was 16.7 months. Multivariate competing risk analysis showed that age (SHR, 1.72; 95% CI, 1.10-2.83, p=0.031), CEA (SHR, 1.94; 95% CI, 1.09-3.46, p=0.024), pT4 (SHR, 2.77; 95% CI, 1.01-7.57, p=0.047), lymph node metastasis (SHR 1.92, 95% CI: 1.09-3.38, p=0.024) and LVI (SHR, 1.84; 95% CI, 1.06-3.20, p=0.028) were independent risk factors for LRR (all p<0.05). The nomogram incorporating these factors achieved good agreement between prediction and actual observation with a concordance index of 0.738 (95% CI, 0.767 to 0.709). In a subgroup analysis of node-positive patients, pN3b was associated with increased peritoneal and distant metastasis (p=0.048). The para-aortic lymph nodes were the most frequent sites (n=71) of LRR, and among them, the 16a2 and 16b1 nodes exhibited even more prevalence (90.1 and 81.7%). Conclusions: Adjuvant radiotherapy might be recommended in gastric cancer patients >= 65 years old or those with pN+, pT4, LVI, or increased CEA levels, particularly in high-risk or pN1-3a patients. The competing risk nomograms may be considered as convenient and individualized predictive tools for LRR in gastric cancer after D2 gastrectomy. It is also recommended that the clinical target volume (CTV) include 16a2 and 16b1 regions of para-aortic lymph nodes.