Treatment heterogeneity and overall survival in patients with advanced/metastatic gastric or gastroesophageal junction adenocarcinoma in the United States.

Background: Gastric or gastroesophageal junction (GEJ) adenocarcinoma is the most common form of gastric cancer diagnosed in the United States (US) each year. Diagnosis typically is in later stages of disease when it has advanced. Patients have been treated with a variety of regimens. Methods: The goal of this retrospective study was to understand if treatment patterns were becoming more homogeneous or remaining heterogeneous using the Herfindahl-Hirschman index (HHI) and if treatments were becoming more concordant to treatment guidelines published by the National Comprehensive Cancer Network (NCCN). HHI scores were calculated for each site by 2-year increments. Trend analyses were conducted for HHI scores over time using a linear regression model. Concordance to Category 1 and any category NCCN guidelines was determined based on the date treatment was initiated with the version of the NCCN guidelines at that time. Time trend analyses were conducted using linear regression models. This study utilized data from the Flatiron Advanced Gastric/Esophageal cohort. This study also examined overall survival (OS) rates estimated by the Kaplan-Meier method by line of therapy. Results: There were no statistically significant differences in HHI scores in the first-line setting over time, suggesting heterogeneity has not improved. Concordance to NCCN treatment guidelines for any category significantly increased over time, however Category 1 regimen concordance remained low in the first-line setting. Concordance over time improved in second-line treatment. Median OS from the start of first-line therapy was 13.57 months. There was no relationship between OS time from initiation of first-line therapy and HHI score, concordance with NCCN guidelines, or concordance with NCCN Category 1 guidelines in the first-line setting. Conclusions: Treatment heterogeneity persists in gastric cancer care, though there is a significant association between heterogeneity and concordance with both Category 1 and any category in the NCCN treatment guidelines, and that concordance has increased over time.