Screening Men for Prostate and Colorectal Cancer in the United States:  Does Practice Reflect the Evidence? FREE

The prostate-specific antigen (PSA) test has been the subject of great hope and controversy since it was first approved for use in 1986 by the US Food and Drug Administration.¹ Although some believe that screening with PSA carries the promise of reducing deaths due to the second most lethal cancer among men, others are concerned that the overall effect of widespread PSA screening will be more prostate cancer diagnoses and potentially harmful therapy without any improvement in outcomes.^2- 8 To our knowledge, there is no valid evidence from randomized controlled trials to help settle this debate,^9- 13 and professional societies are sharply divided in their recommendations.^14- 17

Colorectal cancer screening, on the other hand, is advocated for adults 50 years or older by all major professional medical societies and guideline-issuing organizations.^18- 22 This unanimity is based on the results of several randomized controlled trials, all of which have shown substantial reductions in colorectal cancer mortality among individuals invited to periodic screening with the fecal occult blood test (FOBT).^23- 25 Flexible sigmoidoscopy and colonoscopy, as yet unproven in randomized trials, are believed to confer an even greater mortality benefit than FOBT, based on results of well-conducted case-control trials.^26- 27

Population-based estimates of colorectal cancer screening rates have been widely reported.²⁸ However, although surveys suggest that ordering PSA screening is routine practice for many physicians,^29- 31 it is unknown how many US men are undergoing PSA testing. Therefore, we sought to describe and compare the prevalence of PSA and colorectal cancer screening among men in the United States. If practice were evidence-based, fewer men would undergo PSA screening than colorectal cancer screening.

We used data from the 2001 Behavioral Risk Factor Surveillance System (BRFSS), an annual cross-sectional, population-based, random-digit-dialed telephone survey conducted by the Centers for Disease Control and Prevention. The BRFSS collects data on health care use, risk behaviors, and demographics from a representative sample of civilian noninstitutionalized adults (≥18 years) in each of the 50 states and the District of Columbia.³²

In 2001, for the first time, every state included questions about prostate and colorectal cancer screening in the BRFSS survey. We included 49 315 men aged 40 years or older who responded to at least 1 prostate or colorectal cancer question. Median annual response rate for the 50 states and the District of Columbia, based on persons estimated to be eligible to participate was 51%.³³

Prostate Cancer Screening. All men aged 40 years or older were asked whether they had ever had a PSA test (Box). Those men who responded yes were asked about the timing of the most recent test. Men were also asked whether they had ever been told they had prostate cancer. We report the proportion of men ever tested for prostate cancer (those who reported at least 1 lifetime PSA test) and the proportion up to date on screening. To be up to date, a man had to report a PSA test within the previous year. We considered men with known prostate cancer ineligible for screening and excluded them from the analysis of up-to-date screening (for both prostate and colorectal cancers).

Prostate Cancer Screening

1. A prostate-specific antigen test, also called a PSA test, is a blood test used to check men for prostate cancer. Have you ever had a PSA test?
Yes
No
Don't know/not sure
Refused

2. How long has it been since you had your last PSA test?
Within the past year (anytime <12 months ago)
Within the past 2 years (≥1 year but <2 years)
Within the past 3 years (≥2 years but <3 years)
Within the past 5 years (≥3 years but <5 years)
5 or more years ago
Don't know/not sure
Refused

3. A digital rectal examination is an examination in which a doctor, nurse, or other health professional places a gloved finger into the rectum to feel the size, shape, and hardness of the prostate gland. Have you ever had a digital rectal examination?
Yes
No
Don't know/not sure
Refused

4. How long has it been since your last digital rectal examination?
Within the past year (anytime less than 12 months ago)
Within the past 2 years (≥1 year but <2 years ago)
Within the past 3 years (≥2 years but <3 years ago)
Within the past 5 years (≥3 years but <5 years ago)
5 or more years ago
Don't know/not sure
Refused

5. Have you ever been told by a doctor, nurse, or other health professional that you had prostate cancer?
Yes
No
Don't know/not sure
Refused

Colorectal Cancer Screening

1. A blood stool test is a test that may use a special kit at home to determine whether the stool contains blood. Have you ever had this test using a home kit?
Yes
No
Don't know/not sure
Refused

2. How long has it been since you had your last blood stool test using a home kit?
Within the past year (anytime <12 months ago)
Within the past 2 years (≥1 year but <2 years ago)
Within the past 5 years (≥2 years but <5 years ago)
5 or more years ago
Don't know/not sure
Refused

3. Sigmoidoscopy and colonoscopy are examinations in which a tube is inserted in the rectum to view the bowel for signs of cancer or other health problems. Have you ever had either of these examinations?
Yes
No
Don't know/not sure
Refused

4. How long has it been since you had your last sigmoidoscopy or colonoscopy?
Within the past year (anytime <12 months ago)
Within the past 2 years (≥1 year but <2 years ago)
Within the past 5 years (≥2 years but <5 years ago)
Within the past 10 years (≥5 years but <10 years ago)
10 or more years ago
Don't know/not sure
Refused

Colorectal Cancer Screening For colorectal cancer screening, respondents aged 50 years or older were asked whether and how recently they had had an FOBT and a sigmoidoscopy or colonoscopy. We report the proportions of men ever tested for colorectal cancer (with any of the 3 tests) and up to date on testing. We considered a man up to date if he reported an FOBT within 1 year or a lower endoscopy (sigmoidoscopy or colonoscopy) within 5 years. Respondents were not asked about the indication for colorectal cancer tests or about personal history of colorectal cancer.

Each state's yearly BRFSS data file is weighted to the respondent's probability of selection and the age-specific, sex-specific, and race-specific population from the most current census data (or intercensal estimates) for each state. These weights adjust for differences in probability of selection and nonresponse, and may also partially correct for any bias caused by lack of telephone coverage. Because the poststratification weights reflect the size of the underlying stratum-specific population, we were able to combine data from each state into summary measures (weighted estimates) representing the combined population of the country.

Men who did not respond to questions about ever having had a test (eg, PSA) were excluded from the analysis of that test. Men who reported having had a test but did not respond about the timing of the test were considered not up to date with respect to that test. Item nonresponse rates ranged from 2% to 9% for PSA questions and 0% to 7% for colorectal cancer testing questions.

We analyzed responses based on decade of age, using 5 age categories from 40 to 49 years to 80 years or older. For men aged 50 years or older, we report the risk ratio (RR) of prostate cancer screening compared with colorectal cancer screening using Fisher exact test to calculate 95% confidence intervals (CIs). All analyses were performed using STATA version 7.0 (Stata Corp, College Station, Tex). All reported P values are based on 2-sided tests; P<.05 is considered significant.

In the 50 states and the District of Columbia, 75% of men aged 50 years or older had undergone PSA testing at least once. The likelihood of ever having been tested increased with age until 80 years (Table 1). Eighty-six percent of men aged 70 to 79 years had had at least 1 PSA test. Prostate-specific antigen testing was not uncommon among younger men: 34% of men aged 40 to 49 years had been tested at least once. Up-to-date PSA screening was also common. Fifty-seven percent of men aged 50 years or older reported an up-to-date screening PSA. Elderly men were most likely to be up to date on screening: 69% of men aged 70 to 79 years had an up-to-date PSA. Although rates declined modestly after 80 years, PSA screening remained common with 56% of men 80 years or older reporting an up-to-date screening test.

In contrast with PSA testing, 63% of men aged 50 years or older had undergone colorectal cancer screening using either FOBT or lower endoscopy. As was the case for prostate cancer screening, rates of ever having been tested and of up-to-date screening increased with age until 80 years (Table 1). Lower endoscopy was more common than FOBT as a means of up-to-date colorectal cancer screening among men of all ages.

More men aged 50 years or older had ever been tested for prostate than for colorectal cancer (75% vs 63%; RR, 1.20; 95% CI, 1.18-1.21). Men were also more likely to be up to date on prostate cancer screening than colorectal cancer screening (57% vs 48%; RR, 1.19; 95% CI, 1.17-1.21). Among men aged 50 to 69 years, the age group for which there is the greatest consensus in favor of screening for both cancers,^14- 22 54% of men were up to date on PSA screening compared with 45% for colorectal cancer testing (RR, 1.19; 95% CI, 1.16-1.21). Figure 1 demonstrates the comparison between rates of up-to-date PSA and colorectal cancer screening according to decade of age. Men aged 50 to 59 years were 20% more likely to be up to date on PSA than colorectal cancer screening (RR, 1.20; 95% CI, 1.17-1.24). Up-to-date prostate cancer screening was also significantly more common among men aged 60 to 69 years (RR, 1.17; 95% CI, 1.14-1.20), 70 to 79 years (RR, 1.15; 95% CI, 1.12-1.18), and 80 years or older (RR, 1.08; 95% CI, 1.02-1.14).

In 47 states, men were significantly more likely to have ever had a PSA test than to have ever been tested for colorectal cancer. In Hawaii, Maine, Minnesota, and Vermont, the proportions were similar (Table 2). Rates of up-to-date testing also favored PSA screening. Among men aged 50 to 69 years, for whom consensus in favor of screening is greatest, the median percentage with an up-to-date PSA screen was 53% (range, 45%-61%) compared with 45% (range, 32%-62%) for an up-to-date colorectal cancer test. Figure 2 demonstrates the relationship between rates of up-to-date PSA and colorectal cancer screening within each state. Up-to-date PSA screening was significantly more common than colorectal cancer testing in 27 states. Colorectal cancer testing was more common only in Minnesota; in the remainder, there was no significant difference (Table 2).

We found that PSA testing was common in the United States: 75% of men aged 50 years or older had had a PSA test and 57% were up to date on screening. Prostate-specific antigen screening was particularly common among elderly men, with 69% of men aged 70 to 79 years and 56% of men 80 years or older reporting PSA screening in the past year. If practice were in accordance with evidence of screening-related benefits, colorectal cancer screening would be more common than prostate cancer screening among US men. However, we found this to be the case in only 1 state. Nationally, men in each age group from 50 to 79 years were 15% to 20% more likely to be up to date on PSA screening than colorectal cancer screening.

Although prostate and colorectal cancers are responsible for comparable numbers of deaths among US men each year (in 2002, an estimated 30 200 deaths from prostate cancer and 27 800 from colorectal cancer),³⁴ colorectal cancer is responsible for the large majority of premature deaths among the 2 malignancies (accounting for 2 ½ times as many years of potential life lost before age 75 years as prostate cancer).^35- 37 Furthermore, evidence for a benefit from screening is vastly different for the 2 cancers. Deaths from colorectal cancer were decreased by 14% to 33% in the screening (FOBT) groups of 3 randomized controlled trials involving 250 000 participants in 3 countries.^18,23- 25 In contrast, no valid randomized controlled trial evidence exists regarding the efficacy of prostate cancer screening.^{8- 13,38- 39} In accordance with the evidence, professional societies are divided regarding PSA screening recommendations but uniformly endorse colorectal cancer screening, most commonly FOBT and flexible sigmoidoscopy, for adults aged 50 years or older.^14- 22

There are several possible explanations for our findings that screening practices among US men are discordant with evidence about screening benefits. First, men may be more accepting of a simple blood test (PSA) than the more inconvenient or invasive testing involved in colorectal cancer screening. Second, although media messages have promoted colorectal cancer screening in recent years, these messages have been eclipsed by those of the PSA screening movement, with messages to men to "Get the [PSA] test" from sources as varied as the media, public personalities, and the US Postal Service, in the form of a postage stamp.^40- 41 Lastly, men may perceive themselves to be more vulnerable to prostate than to colorectal cancer. Because the prevalence of prostate cancer is more than 3 times that of colorectal cancer among men older than 40 years³⁴ (in part due to PSA testing), men are more likely to know other men with prostate cancer than with colorectal cancer and to perceive themselves to be at heightened risk of the disease.

It is likely that physicians' ordering practices are influenced by all of these factors, in addition to pressures to adhere to perceived standards of care, meet patient demands, and avoid malpractice liability.³¹ Despite findings that most physicians are unsure about the benefits of PSA testing, the large majority routinely order the test on their male patients.^26,31 On the other hand, although most physicians are aware of strong evidence in favor of colorectal cancer screening, many refrain from recommending testing, primarily because of anticipated patient resistance.^42- 44

There are several limitations in our study. First, some may argue with our criterion for an up-to-date colorectal cancer test. Although we allowed an up-to-date FOBT or lower endoscopy to qualify as up to date on screening, FOBT alone is supported by solid evidence and most professional organizations recommend both tests. Had we strengthened our standard for up-to-date colorectal cancer testing by requiring an up-to-date FOBT or required that both tests be up to date (FOBT and lower endoscopy), the proportion of men in each age group meeting the requirement would have decreased by half. Thus, our use of a liberal standard inflated the estimates of up-to-date colorectal cancer testing, narrowing the gap between colorectal and PSA screening rates.

On the other hand, we may have underestimated the extent of up-to-date colorectal cancer testing, because our data do not allow us to count men with a single colonoscopy more than 5 years ago as up to date on colorectal cancer screening (as many authorities recommend). Data from another national survey, however, enable us to predict that if we were able to count a single lifetime colonoscopy as an up-to-date screen, our estimate of the proportion of men with an up-to-date colorectal cancer screening test would increase by 3%.⁴⁵

Third, because it is a less widely agreed on screening modality, we did not include digital rectal examination as a prostate cancer screening test in our analyses. Including digital rectal examination, which was about as common as PSA screening among men of all ages, would have resulted in a larger disparity favoring prostate cancer screening over colorectal cancer screening. Sixty-six percent of men 50 years or older were up to date on prostate cancer screening based on a PSA test or digital rectal examination within 1 year (compared with 57% with PSA alone).

Lastly, our estimates are based on patient self-reports. Although self-reports of screening behavior have consistently been found to overestimate the extent of actual screening by 20% to 50%,^46- 49 recent evidence suggests lower rates of inaccuracy (10%-30%) for recall of PSA testing^50- 51 and colorectal cancer testing.^52- 53 Moreover, because men are more likely to be aware of and recall having had a do-it-yourself (FOBT) or invasive (lower endoscopy) examination compared with a simple blood test (PSA), the use of self-reported data would be expected to overstate the extent of colorectal cancer screening relative to screening for prostate cancer. Our results may further overstate the extent of colorectal cancer screening, because although we were able to distinguish between screening and surveillance PSA tests in men with known prostate cancer, we were not able to do so for colorectal cancer tests and therefore considered each test a screening test. Another limitation imposed by reliance on self-reported data is that the proportion of men reporting screening may be higher in our study than in actual practice, if those not responding to the survey are less likely to be screened. Thus, we may have overestimated both PSA and colorectal cancer screening rates.

Our study suggests that, despite widespread efforts to improve adherence to colorectal cancer screening guidelines,⁵⁴ such screening is still considerably less common among US men than prostate cancer screening, for which benefits have never been demonstrated. We recommend that physicians ensure that men who choose to be screened for cancer are aware of the known mortality benefit of colorectal cancer screening and the uncertainty about screening for prostate cancer. In addition, given the high rates of PSA screening among elderly men, physicians should ensure that elderly men (those who are least likely to benefit and who may well be harmed by screening) make a well-informed decision about PSA screening.