Rising Incidence of Non-Cardia Gastric Cancer among Young Women in the United States, 2000–2018: A Time-Trend Analysis Using the USCS Database

Simple Summary Although the global incidence of non-cardia gastric cancer (NCGC) is decreasing, there are limited data on sex-specific incidence in the U.S. The aim of our study was to investigate age and sex-specific time trends of NCGC incidence using a large national database from the Surveillance, Epidemiology, and End Results (SEER) Program, and thereafter to externally validate these findings within an independent population-based database, the National Program of Cancer Registries (NPCR). We evaluated the influence of race, histopathology, and disease stage at diagnosis on these trends. NCGC incidence has been relatively increasing at a greater rate in younger women compared to counterpart men over the last two decades, and this rise may be explained by a disproportionate increase in young non-Hispanic White women. Our findings support the increasing incidence of cancers at multiple sites in young women, and emphasize the need for dedicated research to determine the etiologies of these alarming trends. Abstract Introduction: Although the global incidence of non-cardia gastric cancer (NCGC) is decreasing, there are limited data on sex-specific incidence in the United States. This study aimed to investigate time trends of NCGC from the SEER database to externally validate findings in a SEER-independent national database, and to further assess trends among subpopulations. Methods: Age-adjusted incidence rates of NCGC were obtained from the SEER database from 2000 to 2018. We used joinpoint models to calculate average annual percentage change (AAPC) to determine sex-specific trends among older (≥55 years) and younger adults (15–54 years). Using the same methodology, findings were then externally validated using SEER-independent data from the National Program of Cancer Registries (NPCR). Stratified analyses by race, histopathology, and staging at diagnosis were also conducted in younger adults. Results: Overall, there were 169,828 diagnoses of NCGC from both independent databases during the period 2000–2018. In SEER, among those <55 years, incidence increased at a higher rate in women (AAPC = 3.22%, p < 0.01) than men (AAPC = 1.51%, p = 0.03), with non-parallel trends (p = 0.02), while a decreasing trend was seen in both men (AAPC = −2.16%, p < 0.01) and women (AAPC = −1.37%, p < 0.01) of the ≥55 years group. Validation analysis of the SEER-independent NPCR database from 2001 to 2018 showed similar findings. Further stratified analyses showed that incidence is disproportionately increasing in young non-Hispanic White women [AAPC = 2.28%, p < 0.01] while remaining stable in their counterpart men [AAPC = 0.58%, p = 0.24] with non-parallel trends (p = 0.04). This pattern was not observed in other race groups. Conclusion: NCGC incidence has been increasing at a greater rate in younger women compared to counterpart men. This disproportionate increase was mainly seen in young non-Hispanic White women. Future studies should investigate the etiologies of these trends.