Rural-urban and racial/ethnic trends and disparities in early-onset and average-onset colorectal cancer.

BACKGROUND Incidence rates (IRs) of early-onset colorectal cancer (EOCRC) are increasing, whereas average-onset colorectal cancer (AOCRC) rates are decreasing. However, rural-urban and racial/ethnic differences in trends by age have not been explored. The objective of this study was to examine joint rural-urban and racial/ethnic trends and disparities in EOCRC and AOCRC IRs. METHODS Surveillance, Epidemiology, and End Results data on the incidence of EOCRC (age, 20-49 years) and AOCRC (age, ≥50 years) were analyzed. Annual percent changes (APCs) in trends between 2000 and 2016 were calculated jointly by rurality and race/ethnicity. IRs and rate ratios were calculated for 2012-2016 by rurality, race/ethnicity, sex, and subsite. RESULTS EOCRC IRs increased 35% from 10.44 to 14.09 per 100,000 in rural populations (APC, 2.09; P < .05) and nearly 20% from 9.37 to 11.20 per 100,000 in urban populations (APC, 1.26; P < .05). AOCRC rates decreased among both rural and urban populations, but the magnitude of improvement was greater in urban populations. EOCRC increased among non-Hispanic White (NHW) populations, although rural non-Hispanic Black (NHB) trends were stable. Between 2012 and 2016, EOCRC IRs were higher among all rural populations in comparison with urban populations, including NHW, NHB, and American Indian/Alaska Native populations. By sex, rural NHB women had the highest EOCRC IRs across subgroup comparisons, and this was driven primarily by colon cancer IRs 62% higher than those of their urban peers. CONCLUSIONS EOCRC IRs increased in rural and urban populations, but the increase was greater in rural populations. NHB and American Indian/Alaska Native populations had particularly notable rural-urban disparities. Future research should examine the etiology of these trends.