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 versus observation.

Design

Retrospective cohort. 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 AMA Physician Masterfile. Mixed effects models were used to evaluate management variation and factors associated with observation.

Setting

Population-based cancer registries.

Participants

Men age 66 years and older diagnosed with low-risk prostate cancer during the period from 2006 through 2009.

Main Outcome Measure

No cancer-directed therapy within 12 months of diagnosis (observation).

Results

A total of 2145 urologists diagnosed 12,068 men with low-risk prostate cancer. Eighty percent of the patients received treatment, and 20% 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 versus 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 (p=0.01) and graduated in earlier decades (p=0.004) were less likely to manage low-risk disease with observation. Treated patients were more likely to undergo prostatectomy (p<0.001), cryotherapy (p<0.001), brachytherapy (p<0.001), or external-beam radiotherapy (p=0.005) 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 diagnosed by urologists who treated prostate cancer were more likely to receive up-front treatment and, when treated, more likely to receive a treatment their urologist performed. Public reporting of physicians’ cancer-management profiles would enable informed selection of physicians to diagnose and manage prostate cancer.

Introduction

Low-risk prostate cancer (clinical tumor [cT] category T1-T2a, Gleason score ≤ 6 and prostate specific antigen (PSA) < 10 ng/mL) is unlikely to cause symptoms or affect survival if left untreated. However, most men diagnosed with low-risk prostate cancer in the United States (US) receive up-front treatment with prostatectomy or radiotherapy and are thus exposed to the risk of treatment-induced urinary dysfunction, rectal bleeding, and impotence.^1–3 Observation is an alternative to up-front treatment for low-risk prostate cancer and is endorsed by numerous professional societies.^4–6 Randomized trials demonstrate that in older men with low-risk prostate cancer, observation yields similar survival and decreased morbidity compared to up-front treatment.^7,8 Nevertheless, few eligible men opt for observation.¹

Prior studies suggest that the choice of up-front treatment versus observation for early-stage prostate cancer is influenced by patient factors, including age and severity of comorbid conditions.^2,9 It is not known, however, whether management approach is influenced by physician factors, including characteristics of the diagnosing urologist, who conveys the diagnosis and discusses disease severity and management. Primary care providers who refer patients to urologists for prostate biopsy may assume that patients will receive similar management recommendations regardless of the urologist they see. We sought to determine whether this is indeed the case. In a population-based cohort of older men with low-risk prostate cancer, we sought to 1) determine the relative impact of the diagnosing urologist and patient factors on choice of observation versus up-front treatment; 2) quantify the rate of observation versus up-front treatment for individual urologists; and 3) identify urologist and patient factors associated with selection of observation. Since many older men with prostate cancer also meet with a radiation oncologist, we similarly evaluated the impact of the consulting radiation oncologist on the management approach.

Methods

Study subjects

Study subjects were selected from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) database. Under the supervision of the National Cancer Institute, records from the SEER database have been linked to Medicare claims.

The study cohort comprised men age 66 years and older with low-risk prostate adenocarcinoma diagnosed during 2006–2009 (Figure 1). Men with cT2NOS disease likely had low-risk disease as categorization into higher-risk group is usually driven by Gleason score >6 or PSA level ≥10 ng/ml. However, men with cT2NOS disease were excluded in sensitivity analyses. We chose the period 2006–2009 because this was after publication of the Scandinavian Prostate Cancer Group Study Number 4, which showed that among men age 65 years and older with clinically localized prostate cancer, watchful waiting and up-front prostatectomy produced similar survival outcomes.¹⁰ Throughout the period covered by our study, National Comprehensive Cancer Network (NCCN) guidelines recommended observation as a treatment option for men with low-risk prostate cancer.^11,12 Men without continuous fee-for-service Medicare coverage during the 12 months before and after diagnosis were excluded, as their claims would not be sufficient to determine comorbidity and treatment. The study was granted exemption by our institution’s Institutional Review Board.

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.

Outcome

The primary outcome was receipt of prostate cancer treatment within 12 months of diagnosis. Patients were considered to have received up-front treatment if codes for prostatectomy, radiotherapy, cryotherapy, or androgen deprivation therapy were present in either registry or claims data within 12 months of the registry date of diagnosis (eTable 1). Patients not receiving treatment were classified as having observation.

Covariates

Patient-level covariates were age, race/ethnicity, comorbidity, Medicaid coverage, cT category, diagnosis year, and registry. Comorbidity score was calculated from claims submitted during the period from 12 months to 1 month before diagnosis using Klabunde and colleagues’ adaptation of the Charlson comorbidity index.¹³

The diagnosing urologist was identified from Medicare claims (eTable 1) as the urologist who performed the first diagnostic prostate biopsy within 4 months of diagnosis. The consulting radiation oncologist was identified from Medicare claims as the radiation oncologist who delivered radiotherapy or, if the patient did not receive radiotherapy, the first radiation oncologist the patient saw. Physician-level covariates, determined via linkage to the American Medical Association Physician Masterfile, included sex, decade of medical school graduation, medical degree, training location, and board certification. Urologist diagnosis volume and radiation oncologist treatment volume were defined in men with node-negative, nonmetastatic cancer (cohort designated with ^b in Figure 1) and divided into tertiles. A urologist was classified as treating non-low-risk prostate cancer if he or she submitted claims for prostatectomy, cryotherapy, brachytherapy, external-beam radiotherapy, or androgen deprivation therapy for patients with non-low-risk disease (cohort designated with ^c in Figure 1).

Statistical analyses

Descriptive statistics were used to summarize characteristics of urologists, radiation oncologists, and patients. Hierarchical mixed effects models were used to evaluate the odds of observation with patients nested within physicians and to estimate the proportion of variation in the rate of observation attributable to physician-level and patient-level covariates.^14,15 The unit of analysis in the logistic regression was the patient. This multilevel logistic regression model assumes a physician-level random effect, which explicitly considers the interdependencies among patients treated by the same physician. Variance of the random intercept describes heterogeneity in observation rate among physicians after patient-level covariates are accounted for. To measure the impacts of the physician-level and patient-level effects on use of observation, we used the threshold method to estimate the proportion of outcome variance attributable to physician-level or patient-level effects in accordance with published methods.^16,17 Given prior literature^2,9, we included patient age, race/ethnicity, comorbidity, cT category, and PSA level as fixed patient-level covariates in the mixed effects models. Backward selection with p-value cutoff of 0.1 was used to identify additional patient and physician factors for inclusion in the regression model. Physicians who diagnosed at least one patient in the study cohort were included in the main analyses, and patients and physicians with unknown covariate values were excluded from the final model.

Using the hierarchical model adjusted for patient-level covariates, we calculated the case-adjusted rate of observation and 95% CIs for each physician who diagnosed or treated 10 or more patients (patients with unknown covariate values were excluded). Physicians were ranked from lowest to highest, and predicted observation rates were graphed relative to the adjusted mean rate.¹⁶ All analyses were conducted using SAS for Windows, version 9.2 (SAS Institute Inc.).

Results

A total of 12,068 patients with low-risk prostate cancer met the selection criteria (Table 1). Most patients were non-Hispanic white (80%), had cT1 disease (73%), and were seen by a radiation oncologist (68%). The median age was 72 years. These patients were diagnosed by 2145 urologists. Most (88%) urologists treated non-low-risk prostate cancer (Table 2).

Table 1.

Characteristics of 12,068 patients with low-risk prostate cancer.

Characteristic	Number of Individuals	%
Patient characteristics
Age, years
66–70	5068	42.0
71–75	4131	34.2
76–80	2158	17.9
>80	711	5.9
Race/ethnicity
Non-Hispanic white	9612	79.7
Hispanic	691	5.7
Non-Hispanic black	969	8.0
Non-Hispanic other	796	6.6
Comorbidity score
0	8337	69.1
1	2613	21.7
2+	1118	9.3
Medicaid coverage
No	11,113	92.1
Yes	955	7.9
Clinical tumor (cT) category
cT1	8853	73.4
cT2	3215	26.6
PSA level, ng/mL
<4	2052	17.0
4–10	10,016	83.0
Diagnosis year
2006	3274	27.1
2007	3293	27.3
2008	2900	24.0
2009	2601	21.6
Registry
Californiaa	3368	27.9
Connecticut	583	4.8
Detroit	661	5.5
Georgiab	1748	14.5
Hawaii	115	1.0
Iowa	559	4.6
Kentucky	770	6.4
Louisiana	934	7.7
New Jersey	2088	17.3
New Mexico	218	1.8
Seattle	673	5.6
Utah	351	2.9
Seen by radiation oncologist
Yes	8178	67.8
No	3890	32.2
Primary management
Observation	2403	19.9
Prostatectomy	1855	15.4
Brachytherapy	2774	23.0
External-beam radiotherapy (EBRT)	3513	29.1
EBRT and brachytherapy	749	6.2
Cryotherapy	340	2.8
Androgen deprivation therapy	434	3.6

^aGreater California, Los Angeles, San Francisco-Oakland, and San-Jose Monterey.

^bAtlanta and Rural Georgia.

Table 2.

Characteristics of the 2145 diagnosing urologists.

Characteristic	Number of Individuals	%
Physician characteristics
Sex
Female	61	2.8
Male	2047	95.4
Unknown	37	1.7
Decade of graduation
Prior to 1980	906	42.2
1980–1989	572	26.7
After 1990	630	29.4
Unknown	37	1.7
Training location
United States	1827	85.2
Not United States	281	13.1
Unknown	37	1.7
Degree
Doctor of Medicine	2050	95.6
Doctor of Osteopathic Medicine	58	2.7
Unknown	37	1.7
Board certified
Yes	1979	92.3
No	129	6.0
Unknown	37	1.7
Physician volume
Lowest tertile	729	34.0
Middle tertile	703	32.8
Highest tertile	713	33.2
Prostate cancer treatments performed (adds to >100%)
None	253	11.8
Prostatectomy	1128	52.6
Brachytherapy	894	41.7
External-beam radiotherapy	156	7.3
Cryotherapy	216	10.1
Androgen deprivation therapy	1760	82.1

Urologist and patient factors associated with observation

Eighty percent of patients received up-front treatment; 20% were observed (Table 1). In multivariable analysis adjusted for patient-level and urologist-level characteristics, urologists who graduated from medical school more recently were more likely to manage low-risk disease with observation (p=0.004), while urologists with a D.O. (p=0.036) and urologists who treated non-low-risk prostate cancer (p=0.010) were less likely to manage low-risk disease with observation (Table 3). Management with observation was not associated with urologist diagnosis volume (p>0.10, not selected for inclusion in the multivariable model). Older men (p<0.001) and men diagnosed more recently (p<0.001) were more likely to have observation. However, 55% of men older than 80 years received up-front treatment (eTable2).

Table 3.

Diagnosing urologist and patient characteristics associated with observation^a

Characteristic	Number of Urologists	Number of Patients	% of Urologists’ Patients with Disease Managed with Observation	% of Patients with Disease Managed with Observation	Adjusted Odds Ratio	p Value
Physician characteristics
Decade of graduation
Prior to 1980	906	---	19.1	---	[reference]
1980–1989	572	---	20.1	---	1.17 (1.01–1.36)	0.041
After 1990	630	---	21.3	---	1.26 (1.08–1.48)	0.004
Degree
Doctor of Medicine	2050	---	20.1	---	[reference]
Doctor of Osteopathic	58	---	13.4	---	0.66 (0.44–0.97)	0.036
Medicine
Treats non-low-risk prostate cancer
No	246	---	25.0	---	[reference]
Yes	1862	---	19.8	---	0.71 (0.55–0.92)	0.010
Patient characteristics
Age, years
66–70	---	5002	---	13.8	[reference]
71–75	---	4089	---	18.0	1.44 (1.28–1.61)	<0.001
76–80	---	2135	---	30.0	2.95 (2.59–3.36)	<0.001
>80	---	701	---	45.1	5.63 (4.70–6.74)	<0.001
Race/ethnicity
Non-Hispanic white	---	9502	---	18.9	[reference]
Hispanic	---	684	---	18.0	0.94 (0.75–1.17)	0.574
Non-Hispanic black	---	957	---	18.2	1.14 (0.94–1.37)	0.186
Non-Hispanic other	---	784	---	37.1	2.43 (1.99–2.96)	<0.001
Comorbidity score
0	---	8239	---	19.5	[reference]
1	---	2580	---	20.3	1.01 (0.91–1.13)	0.831
2+	---	1108	---	22.9	1.12 (0.95–1.30)	0.168
Clinical tumor (cT) category
cT1	---	8753	---	18.4	[reference]
cT2	---	3174	---	24.4	1.23 (1.10–1.39)	<0.001
PSA level, ng/mL
<4	---	2032	---	22.3	[reference]
4–10	---	9895	---	19.5	0.88 (0.77 – 1.00)	0.055
Diagnosis year
2006	---	3236	---	17.5	[reference]
2007	---	3246	---	17.3	1.01 (0.88–1.15)	0.904
2008	---	2863	---	21.1	1.36 (1.18–1.56)	<0.001
2009	---	2582	---	25.1	1.76 (1.53–2.02)	<0.001
Registry
Californiab	---	3341	---	24.2	[reference]
Connecticut	---	581	---	21.7	1.14 (0.86–1.51)	0.357
Detroit	---	659	---	21.9	0.93 (0.69–1.25)	0.628
Georgiac	---	1709	---	15.1	0.69 (0.55–0.87)	0.001
Hawaii	---	115	---	17.4	0.28 (0.15–0.52)	<0.001
Iowa	---	542	---	14.0	0.61 (0.45–0.84)	0.002
Kentucky	---	757	---	18.9	0.94 (0.69–1.27)	0.675
Louisiana	---	930	---	21.5	0.91 (0.71–1.17)	0.468
New Jersey	---	2062	---	14.6	0.59 (0.48–0.71)	<0.001
New Mexico	---	215	---	22.3	1.03 (0.68–1.57)	0.892
Seattle	---	673	---	22.7	1.11 (0.84–1.45)	0.471
Utah	---	343	---	30.6	1.64 (1.15–2.34)	0.006

^aHierarchical (patients nested within urologists) mixed effects multivariable model evaluating 2108 urologists and 11,927 of their patients. Patients and physicians with unknown covariates were excluded. Age, race/ethnicity, comorbidity, cT category, and PSA level were included on the basis of prior studies in the literature. Inclusion of additional patient characteristics (Medicaid coverage, registry) and urologist characteristics (decade of graduation, training location, degree, board certification, diagnosis volume, treatment of prostate cancer) were considered using backward selection with p-value cutoff of 0.1.

^bGreater California, Los Angeles, San Francisco-Oakland, and San-Jose Monterey.

^cAtlanta and Rural Georgia

Men seen by urologists only were more likely to have observation (43.8%; 1703/3890) than men seen by a radiation oncologist and a urologist (8.6%; 700/8178) (p<0.001). Overall, 71% (1703/2403) of men who had observation saw only a urologist.

In sensitivity analyses, the frequency of observation changed by less than 2% when the definition of up-front treatment was changed to treatment within 6 months of diagnosis or within 18 months of diagnosis. Most (87%) men with observation had subsequent PSA evaluation or prostate biopsy, indicating that their disease was managed with surveillance.

Multilevel analyses estimating the relative contributions of the diagnosing urologist and patient-level fixed effects to the variance in the rate of observation are summarized in eTable 3. The diagnosing urologist was the most influential measured factor, responsible for 16% of the variance in management choice; just 8% of the variance was attributable to measured patient characteristics. The diagnosing urologist remained the most influential factor in sensitivity analyses limited to patients with cT1 disease or patients who did not undergo prostatectomy.

Urologist case-adjusted frequency of observation

Since patient factors impact the likelihood of observation, case-adjusted frequency of observation was estimated for urologists with the characteristics of their patients taken into account. The analysis was limited to 391 providers who diagnosed at least 10 study subjects with low-risk prostate cancer to enable calculation of CIs. The mean case-adjusted rate of observation was 19.7%. The case-adjusted rate of observation varied widely across urologists, from 4.5% to 64.2% (Figure 2). Thirty-one (7.9%) urologists had rates significantly different from the mean (p<0.01). Similar variation was seen in sensitivity analysis of 955 providers who diagnosed at least 5 study subjects.

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).

Impact of type of treatment performed by diagnosing urologist

For the patients who received up-front treatment, we evaluated whether the type of treatment performed by the diagnosing urologist impacted the type of treatment the patient received. Men were more likely to undergo prostatectomy (23.8% vs. 12.4%; p<0.001), cryotherapy (22.0% vs. 1.0%; p<0.001), and brachytherapy (47.5% vs. 21%; p<0.001) if their urologist performed that treatment for non-low-risk disease (Table 4). Similarly, men diagnosed by urologists who billed for external-beam radiotherapy were more likely to receive external-beam radiotherapy (52.7% vs. 42.9%; p<0.001).

Table 4.

Association between type of prostate cancer treatment performed or billed by diagnosing urologist and type of treatment received by patients who had up-front treatment

Type of Treatment Performed or Billed by Diagnosing Urologist	Adjusted Odds Ratio (95% CI; p value) of Receiving Specific Type of Treatment for Low-Risk Prostate Cancera
	Prostatectomy	Cryotherapy	Brachytherapy	External-beam radiotherapy
Prostatectomy	1.71 (1.45–2.01; p<0.001)	1.05 (0.70–1.58; p=0.804)	0.81 (0.70–0.94; p=0.004)	0.84 (0.73–0.96; p=0.011)
Cryotherapy	0.90 (0.72–1.13; p=0.381)	28.2 (19.5–40.9; p<0.001)	0.65 (0.53–0.79; p<0.001)	0.50 (0.40–0.61; p<0.001)
Brachytherapy	0.69 (0.58–0.81; p<0.001)	0.45 (0.31–0.65; p<0.001)	3.41 (2.96–3.93; p<0.001)	0.62 (0.54–0.70; p=0.005)
External-beam radiotherapy	0.94 (0.73–1.22; p=0.658)	0.57 (0.32–1.01; p=0.056)	0.78 (0.62–0.98; p=0.0304)	1.31 (1.08–1.58; p<0.001)

^aHierarchical (patients nested within urologists) mixed effects multivariable models evaluating 1984 urologists and 9546 of their patients who received up-front treatment. Patients and physicians with unknown covariates were excluded. Models were adjusted for patient characteristics (age, race/ethnicity, comorbidity, Medicaid coverage, registry, cT category, PSA level) and urologist characteristics (decade of graduation, training location, degree, board certification, prostate cancer treatment type). Sequential models evaluated the outcome of treatment with prostatectomy, cryotherapy, brachytherapy, and external-beam radiotherapy.

Most patients who underwent prostatectomy (1449/1855; 78%) had prostatectomy performed by the diagnosing urologist.

Impact of radiation oncologist factors

Characteristics of the 870 radiation oncologists who met with study subjects and the 7554 study subjects who met with radiation oncologists are summarized in eTable 4. Ninety-one percent of the men who met with a radiation oncologist received up-front treatment, and 9% were observed (eTable 4). In multivariable analysis, radiation oncologists with a D.O. degree were less likely to manage disease with observation (p=0.02; eTable 5). There was no association between observation and physician treatment volume or decade of graduation (not selected for inclusion in the multivariable model).

In multilevel analyses (eTable 6), 19% of the variance in management choice was attributable to the radiation oncologist and just 3% to measured patient characteristics.

For radiation oncologists who treated at least 10 men with low-risk prostate cancer, case-adjusted rates of observation varied widely, from 2.2% to 46.8% (Figure 3).

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).

Discussion

In this group of older Medicare patients eligible for observation because they had low-risk prostate cancer, 80% received up-front treatment. Case-adjusted rates of observation varied widely across both urologists (from 5% to 64%) and radiation oncologists (from 2% to 47%). The variance in treatment selection attributable to physicians was at least double the variance attributable to measured patient-level characteristics such as age, comorbidity, clinical tumor category, and PSA level. Patients who were diagnosed by urologists who treated non-low-risk prostate cancer were more likely to receive up-front treatment and, when treated, more likely to receive a treatment that their diagnosing urologist used for men with non-low-risk disease. These findings strongly suggest that physicians significantly influence not only decision-making regarding up-front treatment versus observation but also the type of up-front treatment when treatment is selected.

Our findings have implications for policymakers, primary care physicians, and patients. At least two-thirds of men in this cohort had cancer detected by PSA screening (cT1c disease). The U.S. Preventive Services Task Force recommended against PSA screening, stating that “the balance of benefits and harms of prostate cancer screening is heavily influenced by … overtreatment” and its associated morbidity.¹⁸ Our finding of meaningful physician-level variation in management of low-risk prostate cancer implies that the risk of overtreatment varies by physician. Public reporting of physicians’ rates of observation would empower primary care providers and patients to seek out urologists and radiation oncologists who choose observation for suitable patients.^19,20

We postulate that the diagnosing urologist plays an important role in treatment selection because he or she is the first to convey the diagnosis to the patient and discuss disease severity and management options. Physician description of prostate cancer is known to impact patient perception of the seriousness of the condition and to impact treatment choice.²¹ Additionally, patients report that physician recommendation is the most important reason they select a prostate cancer treatment.^21–24 We could not determine which management options were offered to patients or the tone of the recommendations, but other studies have demonstrated that some men with low-risk prostate cancer are not offered observation.^23,25 Diagnosing urologists also refer patients to other physicians for second opinions and radiotherapy. Prostate cancer physician referral networks are relatively stable²⁶; therefore, the management selected may also reflect discussions between the diagnosing urologist and the physicians to whom the patient was referred. However, prior literature indicates that fewer management options are discussed at second consultations than at the primary consultation and that most men who seek a second opinion accept the first management recommendation.^24,27 Additionally, more than two-thirds of the men in our study who had observation saw only a urologist and did not meet with a radiation oncologist, suggesting that urologists play a key role in the selection of observation.

Urologists who treated men with non-low-risk prostate cancer were more likely to manage low-risk disease with up-front treatment rather than observation. A possible explanation is that urologists have witnessed the morbidity of late-stage, aggressive prostate cancer. Financial incentives may also influence management as up-front treatment generates more revenue than observation.²⁸ Concern has been raised that financial interest in radiation equipment by urologists may increase the use of external-beam radiotherapy.²⁹ We could not determine if individual urologists had ownership interest in radiation equipment. However, patients diagnosed by urologists who billed for external-beam radiotherapy were more likely to receive external-beam radiotherapy, a finding consistent with the recent Government Accountability Office report that urologists with financial interest in radiation services are more likely to treat men with intensity-modulated external-beam radiotherapy.³⁰

As seen in other studies, we found that most older men who received up-front treatment underwent radiotherapy. Patients referred for radiation oncology consultation are presumably preselected on the basis of perceived need, interest in radiotherapy, or operative risk. However, case-adjusted rates of observation varied across radiation oncologists, indicating that individual radiation oncologists can influence treatment selection. These findings underscore the importance of the American Society for Radiation Oncology’s recently published recommendations that radiation oncologists and patients not “start management of low-risk prostate cancer without discussing active surveillance.”³¹ Future research will be needed to evaluate whether these recommendations increase rates of observation and lessen interphysician variation.

Although up-front treatment of older men with low-risk prostate cancer can cause morbidity^32,33 without clear survival benefit, only 20% of the men in our cohort had observation. Prospective observational studies of men with low-risk prostate cancer managed with observation with active surveillance (serial PSA testing, digital rectal examination, and repeat biopsy with selective delayed intervention for histologic or PSA progression) report low rates of prostate cancer mortality.³⁴ Furthermore, randomized trials demonstrate that observation does not compromise survival in appropriately selected older men. Men age 65 years and older with clinically localized prostate cancer managed with watchful waiting in the Scandinavian Prostate Cancer Group Study Number 4 (SPCG-4) had prostate cancer metastasis and survival outcomes similar to those in men who underwent prostatectomy.^7,10 Likewise, in the Prostate Cancer Intervention vs. Observation Randomized Trial (PIVOT), observation did not increase prostate cancer or all-cause mortality compared with prostatectomy for men with clinically localized prostate cancer in the PSA-screening era.⁸

Our study and others demonstrate that older men with low-risk prostate cancer are more likely to have observation than are younger men.^2,9,35 However, in our cohort, 70% of men age 76–80 years and 55% of men older than 80 years still received up-front treatment. The high treatment rate in the oldest men is striking since average life expectancy for men age 77 years and older in the US is less than 10 years.³⁶ Older men, especially those with multiple medical conditions, are not thought to gain a survival benefit from treatment of low-risk prostate cancer. Since potential harms outweigh benefits for men with limited life expectancy, current NCCN guidelines recommend observation as the only management option for men with low-risk prostate cancer and a life expectancy of less than 10 years.⁴

As the catchment for this cohort encompassed 26% of the US population, the findings are likely representative of national care patterns and physician variation in the treatment of older men enrolled in fee-for-service Medicare during the study era. Nevertheless, our study has certain limitations. First, we used the most recent available data, but practice patterns may have shifted in subsequent years. Results from the SPCG-4 trial and from expectant-management studies supporting observation were available during the study period, but additional prospective expectant-management studies and the PIVOT trial were published after the study period.^8,34,37–39 Second, although all men were candidates for observation according to NCCN guidelines, we could not measure certain factors that may impact treatment choice, such as number and extent of biopsy cores involved with cancer, family history of prostate cancer, and patient anxiety. These factors may account for some of the residual patient-level variance. Third, Gleason score for prostatectomy patients was based on pathologic examination of the prostatectomy specimen. Therefore, we may have inappropriately excluded men who had biopsy Gleason score upgraded at prostatectomy (thereby overestimating the frequency of observation) or included men who had Gleason score downgraded at prostatectomy (estimated to be less than 1% of the cohort ⁴⁰). However, findings were stable in sensitivity analyses limited to men who did not undergo prostatectomy. Finally, we evaluated frequency of observation but did not distinguish between watchful waiting, active surveillance, and loss to follow-up. However, most men whom we classified in the observation group had subsequent PSA evaluation or prostate biopsy, suggesting that their disease was managed with surveillance.

In summary, there is meaningful physician-level variation in the management of low-risk prostate cancer. Public reporting of physicians’ cancer-management profiles would enable primary care providers and patients to make more informed decisions when selecting a physician to diagnose and manage prostate cancer.