G. Richard, MD, MSPH Naazneen Pal, MPH Eduardo C. Gonzalez, MD Jeanne M. Ferrante, MD Daniel J. Van Durme, MD John Z. Ayanian, MD, MPP Jeffrey P. Krischer, PhD Tampa, Florida, and Boston, Massachusetts Submitted, revised, July 21, 1999. From the Department of Family Medicine (R.G.R., N.P, E.C.G., J.M.F., D.J.V) and the H. Lee Moffitt Cancer Center and Research Institute (R.G.R., J.P.K), University of South Florida, Tampa, and the Division of General Medicine, Department of Medicine, Brigham & Women’s Hospital and the Department of Health Care Policy, Harvard Medical School (J.Z.A.). Reprint requests should be addressed to Richard Roetzheim, MD, MSPH, Department of Family Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, MDC 13, Tampa, FL 33612.
References
BACKGROUND: Policymakers question whether there is a relationship between the number and distribution of physicians and the outcomes for important health conditions. We hypothesized that increasing primary care physician supply would be related to earlier detection of colorectal cancer.
METHODS: We identified incident cases of colorectal cancer occurring in Florida in 1994 (n = 8933) from the state cancer registry. We then obtained measures of physician supply from the 1994 American Medical Association Physician Masterfile and examined the effects of physician supply (at the levels of county and ZIP code clusters) on the odds of late-stage diagnosis using multiple logistic regression.
RESULTS: For each 10-percentile increase in primary care physician supply at the county level, the odds of late-stage diagnosis decreased by 5% (adjusted odds ratio [OR] = 0.95; 95% confidence interval [CI], 0.92 - 0.99; P = .007). For each 10-percentile increase in specialty physician supply, the odds of late-stage diagnosis increased by 5% (adjusted OR = 1.05; 95% CI, 1.02 - 1.09; P = .006). Within ZIP code clusters, each 10-percentile increase in the supply of general internists was associated with a 3% decrease in the odds of late-stage diagnosis (OR = 0.97; 95% CI, 0.95 - 0.99; P = .006), and among women, each 10-percentile increase in the supply of obstetrician/gynecologists was associated with a 5% increase in the odds of late-stage diagnosis (OR = 1.05; 95% CI, 1.01 - 1.08; P = .005).
CONCLUSIONS: If the relationships observed were causal, then as many as 874 of the 5463 (16%) late-stage colorectal cancer diagnoses are attributable to the physician specialty supply found in Florida. These findings suggest that an appropriate balance of primary care and specialty physicians may be important in achieving optimal health outcomes.
There has been great interest in the composition of the physician workforce in the United States.1-7 Most studies have concluded that there is an overabundance of specialist physicians. The adequacy of the supply of primary care physicians, however, has been debated, with some studies concluding that there is a deficit,2,7,8 while others argue the current supply is adequate.9-11
Absent from this debate, however, have been studies demonstrating the effects of physician supply on health-related outcomes. A few investigations have suggested that an oversupply of specialists may contribute to higher health care costs.5,12-14 The health benefits of increasing physician supply are less clear. Hospitalization rates for selected conditions have been correlated with primary care physician supply,15,16 as have access and use of ambulatory health services.17- 20 It is not known, however, whether physician supply affects other health outcomes or to what extent the supply of primary care and specialist physicians independently affect health outcomes.
We examined the effects of physician supply on stage at diagnosis for patients with colorectal cancer in Florida during 1994. Colorectal cancer is the second leading cause of cancer mortality in the United States, and stage at diagnosis is the most important prognostic determinant.21 Physicians can diagnose colorectal cancer at an earlier stage by eliciting and promptly evaluating signs and symptoms and by providing recommended screening tests, including fecal occult blood testing and flexible sigmoidoscopy.22 Studies23-28 have consistently shown that access to health care and a physician’s recommendation for screening are important predictors of cancer screening. It might be expected, therefore, that the early detection of colorectal cancer would be dependent on the availability of physician services.
As a marker of access to physician services,29,30 we hypothesized that increasing physician supply would be associated with earlier stage at diagnosis for colorectal cancer. We also hypothesized that the supply of primary care physicians, because of their responsibility to provide comprehensive preventive care, would be a more important determinant of cancer stage than the supply of non–primary-care specialists. In addition, we hypothesized that the supply of family physicians/general internists would be more likely related to stage at diagnosis than other primary care specialties because of the inclusion of sigmoidoscopy in their training and practice.31-35 One study that included Florida family physicians, for example, found that more than 50% reported performing sigmoidoscopy in their office.36
Methods
Sources of Data
Incident cases of colorectal cancer (n = 9551) occurring in 1994, the most current year for which all relevant data were available, were identified from the Florida Cancer Data System (FCDS), a population-based statewide cancer registry. The FCDS has well-established methods to ensure complete case finding (including cooperative arrangements with other state tumor registries) and standardized procedures for quality control. Study cases included cancers of the colon, rectosigmoid junction, and rectum. We excluded tumors of the anal canal.
