Primary Care Physician Supply and Colorectal Cancer
STUDY DESIGN: We performed an ecologic study of Florida’s 67 counties, using data from the state tumor registry and the American Medical Association physician masterfile.
POPULATION: Florida residents were included.
OUTCOMES MEASURED: We measured age-adjusted colorectal cancer incidence and mortality rates for Florida’s 67 counties during the period 1993 to 1995.
RESULTS: Increasing primary care physician supply was negatively correlated with both colorectal cancer (CC) incidence (CC = -0.46; P < .001) and mortality rates (CC = -0.29; P =.02). In linear regression that controlled for other county characteristics, each 1% increase in the proportion of county physicians who were in primary care specialties was associated with a corresponding reduction in colorectal cancer incidence of 0.25 cases per 100,000 (P < .001) and a reduction in colorectal cancer mortality of 0.08 cases per 100,000 (P=.008).
CONCLUSIONS: Incidence and mortality of colorectal cancer decreased in Florida counties that had an increased supply of primary care physicians. This suggests that a balanced work force may achieve better health outcomes.
It was predicted that more than 130,000 Americans would develop colorectal cancer in the year 2000. This is the second leading cause of cancer mortality in the United States, with an estimated 56,300 deaths predicted for 2000.1 In that year, the state of Florida ranked third in the number of colorectal cancer cases (9100) and colorectal cancer deaths (3900).
Earlier diagnosis of colorectal cancer, with subsequently reduced mortality, can be achieved by eliciting and promptly evaluating signs and symptoms of colorectal cancer and by providing recommended screening tests, such as fecal occult blood testing and flexible sigmoidoscopy.2 Also, the provision of screening tests may reduce colorectal cancer incidence by detecting and eliminating precancerous polyps. Annual fecal occult blood testing, for example, has been demonstrated to reduce colorectal cancer incidence by 20%.3 Polyps found by screening sigmoidoscopy would also generally result in surveillance colonoscopy, a procedure which may reduce colorectal cancer incidence by as much as 90%.4
Studies have consistently reported that access to health care and a physician’s recommendation for screening are important predictors of cancer screening.5-10 One would expect, therefore, that the provision of colorectal cancer screening tests would be dependent to some extent on the availability of physician services. Physician specialties may differ, however, in their provision of preventive health services. Stange and colleagues,11 for example, found that family physicians addressed at least one US Preventive Services Task Force recommendation for preventive care in 39% of visits for chronic illness. In contrast, evidence suggests that most specialists are not likely to address health care needs outside their specialty.12
Compared with other cancer screening tests, colorectal cancer screening is less frequently recommended by physicians and is less frequently completed by patients. It is possible, therefore, that the availability of primary care providers has relatively limited impact on colorectal cancer outcomes.13-15 We have previously shown that increasing supplies of primary care physicians were associated with earlier detection of colorectal cancer, while increasing supplies of non–primary care physicians were associated with later-stage diagnosis.16 We hypothesized, therefore, that increasing primary care physician supply would also be associated with lower incidence and mortality rates for colorectal cancer.
Methods
We performed an ecologic study comparing primary care physician supply with colorectal cancer incidence and mortality rates. Colorectal cancer incidence and mortality rates for Florida’s 67 counties were identified using the Florida Cancer Data System (FCDS), a population-based statewide cancer registry. The FCDS is a member of the North American Association of Central Cancer Registries (NAACCR). NAACCR audits have estimated that the completeness of case ascertainment for the period 1990 to 1994 is 99.7%. The FCDS provides age-adjusted incidence and mortality rates by standardizing them to the 1970 US standard population. To account for year-to-year fluctuations, rates were averaged over the 3-year period 1993 to 1995.
Because distal cancers may be more easily detected with screening tests such as sigmoidoscopy, we also examined incidence rates stratified by proximal versus distal origin of the cancer. We defined proximal cancers as those arising from the cecum, ascending colon, hepatic flexure, transverse colon, and splenic flexure. Distal cancers were defined as those arising from the descending colon, sigmoid colon, rectosigmoid juncture, and the rectum. Tumors of the anal canal were excluded because of differing pathology and treatment implications.17
We used the 1990 US census to ascertain other characteristics of Florida counties that might have an impact on colorectal cancer incidence and mortality. In addition to age, colorectal cancer incidence and mortality rates vary by race, socioeconomic status, and marital status. Variables obtained for each county included median household income, percentage of county residents with less than a high school education, percentage residing in urban census areas, percentage who were white, and percentage who were married.
