Physician variation in management of low-risk prostate cancer: a population-based cohort study

Abstract

Importance: Up-front treatment of older men with low-risk prostate cancer can cause morbidity without clear survival benefit; however, most such patients receive treatment instead of observation. The impact of physicians on the management approach is uncertain.

Objective: To determine the impact of physicians on the management of low-risk prostate cancer with up-front treatment vs observation.

Design, setting, and participants: Retrospective cohort of men 66 years and older with low-risk prostate cancer diagnosed from 2006 through 2009. Patient and tumor characteristics were obtained from the Surveillance, Epidemiology, and End Results cancer registries. The diagnosing urologist, consulting radiation oncologist, cancer-directed therapy, and comorbid medical conditions were determined from linked Medicare claims. Physician characteristics were obtained from the American Medical Association Physician Masterfile. Mixed-effects models were used to evaluate management variation and factors associated with observation.

Main outcomes and measures: No cancer-directed therapy within 12 months of diagnosis (observation).

Results: A total of 2145 urologists diagnosed low-risk prostate cancer in 12,068 men, of whom 80.1% received treatment and 19.9% were observed. The case-adjusted rate of observation varied widely across urologists, ranging from 4.5% to 64.2% of patients. The diagnosing urologist accounted for 16.1% of the variation in up-front treatment vs observation, whereas patient and tumor characteristics accounted for 7.9% of this variation. After adjustment for patient and tumor characteristics, urologists who treat non-low-risk prostate cancer (adjusted odds ratio [aOR], 0.71 [95% CI, 0.55-0.92]; P = .01) and graduated in earlier decades (P = .004) were less likely to manage low-risk disease with observation. Treated patients were more likely to undergo prostatectomy (aOR, 1.71 [95% CI, 1.45-2.01]; P < .001), cryotherapy (aOR, 28.2 [95% CI, 19.5-40.9]; P < .001), brachytherapy (aOR, 3.41 [95% CI, 2.96-3.93]; P < .001), or external-beam radiotherapy (aOR, 1.31 [95% CI, 1.08-1.58]; P = .005) if their urologist billed for that treatment. Case-adjusted rates of observation also varied across consulting radiation oncologists, ranging from 2.2% to 46.8% of patients.

Conclusions and relevance: Rates of management of low-risk prostate cancer with observation varied widely across urologists and radiation oncologists. Patients whose diagnosis was made by urologists who treated prostate cancer were more likely to receive up-front treatment and, when treated, more likely to receive a treatment that their urologist performed. Public reporting of physicians' cancer management profiles would enable informed selection of physicians to diagnose and manage prostate cancer.

Figure 1. Cohort sel ection criteria

^aThis step excluded patients who were diagnosed by transurethral resection of the prostate alone, patients diagnosed in the Veterans Affairs or military medical system, in which claims are not submitted, and patients whose diagnostic biopsy was performed by a non-urologist. There were no clinically meaningful differences between men who were and were not matched to a diagnosing urologist. ^bThese men were used to determine urologist diagnosis volume and radiation oncologist treatment volume. ^cThese men who did not have low-risk prostate cancer were used to determine whether or not the urologist treated non-low-risk prostate cancer. ^dSince men with cT2NOS disease could have higher-volume disease, men with cT2 disease were excluded in sensitivity analyses.

Figure 2. Case-adjusted frequency of management of low-risk prostate cancer with observation for individual urologists

Case-adjusted frequency of observation by rank, from lowest (4.5%) to highest (64.2%), for 391 urologists who diagnosed at least 10 men with low-risk prostate cancer in the study cohort (blue line). Frequency of observation is adjusted for patient age, race/ethnicity, comorbidity, Medicaid coverage, clinical tumor category, and PSA level. Mean case-adjusted frequency of observation was 19.7% (red line). The 95% CI bars take into account variability of the calculated rate based on the size of the patient panel. Black bars represent 31 urologists who had rates significantly different from the mean (p<0.05).

Figure 3. Case-adjusted frequency of management of low-risk prostate cancer with observation for individual radiation oncologists

Case-adjusted frequency of observation by rank, from lowest (2.2%) to highest (46.8%), for 226 radiation oncologists who saw at least 10 men with low-risk prostate cancer in the study cohort (blue line). Frequency of observation is adjusted for patient age, race/ethnicity, comorbidity, Medicaid coverage, clinical tumor category, and PSA level. Mean case-adjusted frequency of observation was 8.5% (red line). The 95% CI bars take into account variability of the calculated rate based on the size of the patient panel. Black bars represent radiation oncologists who had rates significantly different from the mean (p<0.05).