written by reader Pros & Cons of Screening for Breast and Prostate Cancer

The old news, by now a couple of years old, is that the U. S. Preventive Services Task Force (USPSTF) has recommended against routine screening of women aged 40 to 49 years for breast cancer, and also recommended against screening for prostate cancer for men at any age using the prostate-specific antigen (PSA) test.

The newer news is that a lot of the evidence, perhaps most of it, appears to be contrary to the USPSTF’s recommendations. And the big question is, why did the USPSTF come to these conclusions?

Who, or What, Is the USPSTF?

Here’s what they say about themselves:

“U.S. Preventive Services Task Force

The USPSTF is an independent panel of non-Federal experts in prevention and evidence-based medicine and is composed of primary care providers (such as internists, pediatricians, family physicians, gynecologists/obstetricians, nurses, and health behavior specialists).

The USPSTF conducts scientific evidence reviews of a broad range of clinical preventive health care services (such as screening, counseling, and preventive medications) and develops recommendations for primary care clinicians and health systems. These recommendations are published in the form of ‘Recommendation Statements.’

AHRQ’s Prevention and Care Management Portfolio provides ongoing administrative, research, technical, and dissemination support to the USPSTF.

About the USPSTF

The USPSTF strives to make accurate, up-to-date, and relevant recommendations about preventive services in primary care.

To learn more detailed information about the USPSTF, including how it operates, current members and partners, and background information, visit http://www.uspreventiveservicestaskforce.org/about.htm

Methods and Processes

For the USPSTF to recommend a service, the benefits of the service must outweigh the harms. The USPSTF focuses on maintenance of health and quality of life as the major benefits of clinical preventive services, and not simply the identification of disease.”

AHRQ, by the way, is the Agency for Healthcare Research and Quality, which is part of the U. S. Department of Health and Human Services. Nobody, as far as I can tell, has accused either the USPSTF or the AHRQ of not being conscientious and on the up & up. My ornery turn of mind, however, suspects the USPSTF of keeping a sharp eye on healthcare costs in general, and of being perhaps excessively reluctant to recommend treatments or procedures that, although they might benefit some patients, cannot be demonstrated to meet certain standards of cost effectiveness. That might be my prejudice, but let’s see how their recommendations stand up in the light of the evidence.

The Mammography Recommendations

Back in 2002, the USPSTF issued a recommendation for screening mammograms for all women 40 years of age or older. The recommendation went on to say that

“Clinicians should inform women about the potential benefits (reduced chance of dying from breast cancer), potential harms (for example, false-positive results, unnecessary biopsies), and limitations of the test that apply to women their age.”

However, in November of 2009, they issued an update:

“The USPSTF now recommends against routine screening of women aged 40 to 49 years (C recommendation), recommends biennial screening mammography for all women aged 50 to 74 years (B recommendation), and provides an I statement regarding screening for women older than 75 years.”

Here, by the way, if you’re interested, is what the USPSTF says those recommendations mean:

What the Grades Mean and Suggestions for Practice

Grade

Definition

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Suggestions for Practice

A

The USPSTF recommends the service. There is high certainty that the net benefit is substantial. Offer or provide this service.

B

The USPSTF recommends the service. There is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial. Offer or provide this service.

C

Note: The following statement is undergoing revision.
Clinicians may provide this service to selected patients depending on individual circumstances. However, for most individuals without signs or symptoms there is likely to be only a small benefit from this service.
Offer or provide this service only if other considerations support the offering or providing the service in an individual patient.

D

The USPSTF recommends against the service. There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits. Discourage the use of this service.

I Statement

The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the service. Evidence is lacking, of poor quality, or conflicting, and the balance of benefits and harms cannot be determined. Read the clinical considerations section of USPSTF Recommendation Statement. If the service is offered, patients should understand the uncertainty about the balance of benefits and harms.

Talk about carefully hedged! But now, let’s take a look at the “evidence” that they themselves cite:

They base their conclusion on several clinical trials and meta-analyses. (A meta-analysis combines the results from several trials or studies, even if the ground rules by which the trials were conducted are different – i.e., patients of different ages or with different risk factors, etc.) In women in their 40s who were screened via mammograms, the risk ratios for death from death cancer in these studies averaged 0.85, meaning that they had a 15% reduction in breast cancer mortality, compared with the women who had not had mammograms. That’s not nothing!

Here are the pooled results (USPSTF figures) for four age brackets:

Table 1. Pooled RRs for Breast Cancer Mortality From Mammography Screening Trials for All Ages

Age

Trials Included,
n

RR for Breast Cancer
Mortality (95% CrI)

NNI to Prevent 1 Breast
Cancer Death (95% CrI)

39-49 y 8* 0.85 (0.75-0.96) 1904 (929-6378)
50-59 y 6a 0.86 (0.75-0.99) 1339 (322-7455)
60-69 y 2b 0.68 (0.54-0.87) 377 (230-1050)
70-74 y 1c 1.12 (0.73-1.72) Not available

CrI = credible interval; NNI = number needed to invite to screening; RR = relative risk.
* Health Insurance Plan of Greater New York,27 Canadian National Breast Screening Study-1,28 Stockholm,26 Malmö,26 Swedish Two-County trial (2 trials),26,31 Gothenburg trial,30 and Age trial.29
a Canadian National Breast Screening Study-1,28 Stockholm,26 Malmö,26 Swedish Two-County trial (2 trials),26,31 and Gothenburg trial.30
b Malmö26 and Swedish Two-County trial (Östergötland).26
cSwedish Two-County trial (Östergötland).26

The last column is where we find the data that pushed the USPSTF over the edge. NNI, in case you missed the tiny footnote, is the “number needed to invite to screening” to prevent one breast cancer death. Whereas for women aged 60 to 69, that number is 377, and for women aged 50 to 59 it is 1339, for women aged 39 to 49 it is 1904. What the USPSTF is saying is that it’s not worth screening 1904 women in their 40s to prevent one death, whereas it is worth screening 1339 women in their 50s and 377 women in their 60s to prevent one death. It seems to boil down to an economic calculation.

Now, according to the U. S. Census Bureau, in 2011 there were 21,604,000 women in our country between the ages of 40 and 49. My little pocket calculator, which has never lied to me, tells me that if all these women had mammograms, it could result – if you trust those figures from the USPSTF – it could result in preventing 11,347 deaths from breast cancer

I feel like putting that in large bold type: mammograms for women in their 40s could result in preventing 11,347 deaths from breast cancer.

So why did they change their recommendation? Let’s take a look at the “harms” they mention as offsetting the benefits (i.e. not dying of breast cancer). These harms include radiation exposure, pain during the procedure, anxiety and distress, and possible false positives resulting in unnecessary biopsies. They themselves minimize the risk of radiation exposure, note that few women consider the pain as a deterrent from future mammograms, and state that false-positive mammograms had no consistent effect on women’s general anxiety and depression. Are those “harms” enough to recommend that women in their 40s forego a procedure that could save their lives?

In the meantime, what has been happening is that the number of screenings has been declining, and along with that, the number of cancers detected has been declining. For example at the New York Presbyterian-Weill Cornell Medical Center from 2007 through 2010, 43,351 screenings were done and 205 breast cancers were found, 19% of which were in women in their 40s, and half of that 19% were of the invasive type. Those are cancers that spread through the breast tissue rapidly and need to be treated promptly, but, of course, if they are not detected they won’t be treated. In another study, researchers found that mammograms increased at a rate of 0.9% yearly from 2006 to 2009, but when the USPSTF recommendations were issued in 2009, the rate of mammography declined by 4.3%. That means fewer cancers detected, fewer cancers treated, and more deaths.

My take on this: the recommendations of the USPSTF in this particular case have done more harm than good.

And Now, What About Prostate Cancer Screening?

That issue is a good deal more complicated, and I won’t be doing anyone any favors by waltzing over the difficulties. These come bubbling up from two sources – one, the disease process itself, and two, the nature of the prostate specific antigen (PSA) test.

Here’s the thing about prostate cancer: it mostly affects older men, and it progresses fairly slowly. The statistics are illuminating. The median age for diagnosis of prostate cancer is 66, less than 1% of the cases are seen in men younger than 44, and less than 10% in men younger than 54. According to SEER data (Surveillance Epidemiology and End Results, from the National Cancer Institute), prostate cancer mortality is 23 per 100,000, but in black men it’s more than double that – 50.9 per 100,000. The reasons for this huge discrepancy are not entirely clear, but the guess is that it has a lot to do with both treatment and screening.

In many cases prostate cancer progresses quite slowly. The common wisdom is that men die with it, but not of it. Something else gets us first. However, this may be changing – as mortality diminishes from other common diseases such as heart disease and stroke, many men live longer, giving even slow-growing prostate cancers time to grow and become fatal.

And, here’s the thing about the PSA test: it’s not very good, either in terms of sensitivity or specificity. The test has been in use since 1986, and for much of that time doctors thought that a level of 4.0 ng/mL (nanograms per milliliter) was the cut point for a follow-up. However, men with a condition called benign prostatic hyperplasia (BPH) can have elevated PSA levels, as can men with urinary tract infections. And some men can have prostate cancer without having elevated PSA levels. So, what’s to be done? Toss the whole thing in the garbage can and trust that we’ll be struck by lightning before prostate cancer gets us?

That’s not quite what the USPSTF says, but it amounts to the same thing:</