Abstract
BACKGROUND AND AIMS: The burden of early-onset colorectal cancer (EoCRC) has been increasing among young adult populations in the U.S. The aim of this study was to investigate the relationship between the incidence and mortality of EoCRC and the supply of gastroenterology (GI) specialists and primary care physicians (PCP). METHODS: This was an ecological study of EoCRC cases among US counties that occurred between 2014 and 2018. Data was obtained from US cancer statistics. County-level data, including sociodemographic (eg, percentage of female, non-White residents, poverty rate, rurality) and physician supply (GI specialists and PCPs) was obtained from area health resources files. We estimated linear mixed-effects models with the county as a random effect to examine the association of physician supply with 5-year average age-adjusted EoCRC incidence and mortality. Models were adjusted for aggregate county-level socioeconomic characteristics. Multicollinearity was tested through variation inflation. RESULTS: Analysis included 855 US counties. Mean age-adjusted EoCRC incidence and mortality rates between 2014-2018 were 9.5 (standard deviation [SD]: 2.7) and 2.7 (SD: 0.8) per 100,000 persons, respectively. In the adjusted model, GI supply was associated with lower EoCRC incidence (-5.6 percentage-point change per SD; 95% confidence interval, -11.0 to -0.1) but not with EoCRC mortality (P = .558). PCP supply was associated with lower EoCRC mortality (-27.0 percentage-point change per SD; 95% confidence interval, -46.1 to -7.8) but not with EoCRC incidence (P = .077). CONCLUSION: Greater GI specialist supply was associated with a reduction in EoCRC incidence but not improved mortality. Study findings suggest the need for early colorectal cancer screening efforts and the potential for expanding GI services and referrals in medically underserved areas.