Understanding the association between clinical staging accuracy, treatment response, and survival among gastric cancer patients through Bayesian analysis.

Background: Neoadjuvant therapy (NAT) improves survival among patients with locally advanced gastric cancer (GC), but it remains unclear whether its benefit is contingent on treatment response.

Methods: This is a national cohort study of stage Ib-III GC patients in the National Cancer Data Base (2006-2015) treated with upfront resection or NAT followed by surgery. Bayesian analysis was used for NAT patients to ascertain staging concordance and to account for down-staging. We used multivariable Cox regression to evaluate the association between staging concordance, treatment, response to NAT, and survival.

Results: The cohort included 13 340 patients treated at 1124 hospitals. Staging concordance ranged from 86.1% for cT3-4N+ to 34.7% for cT2N0 patients. Relative to accurately staged patients treated with upfront surgery, NAT was associated with a decreased risk of death if there was disease down-staging among those with cT1-2N+ (hazard ratio [HR]: 0.43 [0.30-0.61]), cT3-4N0 (HR: 0.69 [0.54-0.88]), and cT3-4N+ (HR: 0.51 [0.48-0.58]) tumors, and in the absence of down-staging among cT3-4N+ patients (HR: 0.83 [0.74-0.92]). Conversely, NAT without down-staging increased the risk of death among those with intermediate-stage disease.

Conclusions: NAT is associated with improved survival for GC, but it seems to be contingent on treatment response among patients with intermediate-stage disease.