Regional-Level Correlations in Inappropriate Imaging Rates for Prostate and Breast Cancers: Potential Implications for the Choosing Wisely Campaign.

IMPORTANCE The association between regional norms of clinical practice and appropriateness of care is incompletely understood. Understanding regional patterns of care across diseases might optimize implementation of programs like Choosing Wisely, an ongoing campaign to decrease wasteful medical expenditures. OBJECTIVE To determine whether regional rates of inappropriate prostate and breast cancer imaging were associated. DESIGN, SETTING, AND PARTICIPANTS Retrospective cohort study using the the Surveillance, Epidemiology, and End Results-Medicare linked database. We identified patients diagnosed from 2004 to 2007 with low-risk prostate (clinical stage T1c/T2a; Gleason score, ≤6; and prostate-specific antigen level, <10 ng/mL) or breast cancer (in situ, stage I, or stage II disease), based on Choosing Wisely definitions. MAIN OUTCOMES AND MEASURES In a hospital referral region (HRR)-level analysis, our dependent variable was HRR-level imaging rate among patients with low-risk prostate cancer. Our independent variable was HRR-level imaging rate among patients with low-risk breast cancer. In a subsequent patient-level analysis we used multivariable logistic regression to model prostate cancer imaging as a function of regional breast cancer imaging and vice versa. RESULTS We identified 9219 men with prostate cancer and 30,398 women with breast cancer residing in 84 HRRs. We found high rates of inappropriate imaging for both prostate cancer (44.4%) and breast cancer (41.8%). In the first, second, third, and fourth quartiles of breast cancer imaging, inappropriate prostate cancer imaging was 34.2%, 44.6%, 41.1%, and 56.4%, respectively. In the first, second, third, and fourth quartiles of prostate cancer imaging, inappropriate breast cancer imaging was 38.1%, 38.4%, 43.8%, and 45.7%, respectively. At the HRR level, inappropriate prostate cancer imaging rates were associated with inappropriate breast cancer imaging rates (ρ = 0.35; P < .01). At the patient level, a man with low-risk prostate cancer had odds ratios (95% CIs) of 1.72 (1.12-2.65), 1.19 (0.78-1.81), or 1.76 (1.15-2.70) for undergoing inappropriate prostate imaging if he lived in an HRR in the fourth, third, or second quartiles, respectively, of inappropriate breast cancer imaging, compared with the lowest quartile. CONCLUSIONS AND RELEVANCE At a regional level, there is an association between inappropriate prostate and breast cancer imaging rates. This finding suggests the existence of a regional-level propensity for inappropriate imaging utilization, which may be considered by policymakers seeking to improve quality of care and reduce health care spending in high-utilization areas.