Rural-Urban Differences in Access to Specialist Providers of Colorectal Cancer Care in the United States: A Physician Workforce Issue. 
Although early detection and treatment of colorectal cancer has been shown to improve outcomes, geographic proximity may influence access to these services.  To examine the disparities that may exist in colorectal cancer screening and treatment by comparing the distribution of providers of these services in rural and urban counties in the United States.  A retrospective population-based study using data obtained from the 2009 Area Resource File for the entire US population within each county.  Counties in the United States were categorized as rural or urban using rural-urban continuum codes as our primary exposure.  The proportion of gastroenterologists, general surgeons, and radiation oncologists per 100,000 people in each county was estimated as primary outcomes.  Multivariate linear regression analysis adjusted for county-level socioeconomic variables, such as percentages of females, blacks, population without insurance, those with a high school diploma, and median household income, to estimate the relative density of each category of these providers between urban and rural counties.  In total, 3220 counties were identified, comprising 1807 rural and 1413 urban counties.  An unadjusted analysis showed an increased density of gastroenterologists, general surgeons, and radiation oncologists per 100,000 people in urban vs rural counties.  A multivariable analysis revealed a significantly higher density of gastroenterologists (1.63; 95% CI, 1.40-1.85; P < .001), general surgeons (2.01; 95% CI, 1.28-2.73; P < .001), and radiation oncologists (0.68; 95% CI, 0.59-0.77; P < .001) per 100,000 people living in urban vs rural counties.  A rural-urban disparity exists in the density of gastroenterologists, general surgeons, and radiation oncologists who traditionally provide colorectal cancer screening services and treatment.  This might affect access to these services and may negatively influence outcomes for colorectal cancer in rural areas.