22 Oct, 11 | by EBM
Does Belief-based medicine trump EBM? breast and prostate cancer screening recommendations redux
It has been an exasperating couple of weeks and there will be more to come. I got my coffee and sat down, thinking I could rest a bit and gather strength for the day while a grand rounds speaker droned on. But then it happened—the radiology professor began to build her case for screening all women 40-49 years of age for breast cancer. She spoke as if her case was airtight. She was about to be surprised by audience reaction. The US Preventive Services Task Force (USPSTF) had gotten it wrong she implied, and we are still reeling from it two years later. They shouldn’t have changed their recommendation.
In 2009, the USPSTF revised its recommendation. Here it is (http://bit.ly/aJJ6O7):
“The USPSTF recommends against routine screening mammography in women aged 40 to 49 years. The decision to start regular, biennial screening mammography before the age of 50 years should be an individual one and take into account patient context, including the patient’s values regarding specific benefits and harms. (Grade C recommendation)”
“C” means: “There may be considerations that support providing the service in an individual patient. There is moderate or high certainty that the net benefit is small.” It does say “recommends against” but also says to consider values about benefits and harms. Seems reasonable doesn’t it?
The speaker went on: Since screening was implemented breast cancer mortality has declined. Screening detects early stage tumors, those we can treat before they get worse. And young women get breast cancer, the really bad aggressive kind. At our hospital in the past 3 years, some 79 women in that age group were diagnosed with cancer. And the USPSTF doesn’t think we should screen them all. These are young women with families and jobs. They don’t even want us to recommend women do self-exams. Unbelievable.
A few colleagues rumbled. They asked “Was the decline in mortality due to screening?” “Were the 79 detected by screening?” Fair questions but peripheral, I thought. I felt it coming. I boiled over with “What proportion of women screened versus not screened die from breast cancer? Shouldn’t that be the starting point for the discussion?” The conference ended without an answer though impressive sounding relative risks were presented.
A particularly insightful colleague pointed out that while we might want to know the numbers I asked for, that patients might have trouble understanding them, and more importantly, even when they did understand, they had little context for decision-making. They might be anxious and just want to know what they should do. “What would you do?” or “What do you think I should do?” they would ask their doctor. I had gathered strength for the day, not by snoozing through a lecture but by being energized about the battles between evidence-based medicine and whatever the alternative is.
This was the week after the USPSTF had downgraded its prostate cancer screening recommendation to recommending against it (a Grade D recommendation: means they discourage use of the test because there is moderate to high certainty that it has no net benefit or that harms outweigh the benefits). http://bit.ly/q0Lkyv
A US presidential candidate condemned the recommendation. http://nyti.ms/mZg9kQ And a CEO of a group devoted to ending prostate cancer said that the recommendation “condemns tens of thousands of men to die this year and every year going forward…” http://bo.st/pPaCQg
Seriously? People who spent months to years reviewing the best evidence did that? Here is the evidence: One trial found a 0.07% decrease, another a 0.03% increase, and a meta-analysis, no difference in prostate cancer deaths attributable to screening. And yes, those zeroes and decimals are in the correct places. And harms abound. There was a voice of reason in a physician-written editorial to the New York Times that addressed both breast and prostate cancer screening. http://nyti.ms/poNJ5i
So what is going on?
Belief is powerful. We believe in pathophysiology, and well we should. Early stage tumors become late stage tumors. Sometimes early stage tumors can be removed and the later stage ones prevented. Though inconvenient, it also turns out that in some cancers (eg breast) early stage tumors are manifestations of an already systemic disease, and in others (eg prostate), tumors may not cause harm during the patient’s lifetime. Screening might not help those.
Memory is powerful (the availabity heuristic). We remember the young man or woman who died a horrible cancer death. It was a cancer we had a test for. And we hadn’t tested for it. Their family might complain that they hadn’t been tested. A colleague pointed out to me that no patient had ever complained about getting screened. Even when they suffered all of the downstream consequences (eg surgical complications, erectile dysfunction, incontinence) they were grateful for having been saved (of course one doesn’t know whether he would have been saved without intervention or complications).
The ecology of health care first described in the 1960s by Kerr White continues to be ignored. http://bit.ly/mQdULM Most people do not end up in the care of hospitals or specialists. Yet those who view healthcare through a tertiary care lens are often the most respected, influential and vocal promoters of what should be done for populations and patients in primary care settings, where they have no expertise. (others with no discernable expertise in this arena include politicians, yet they speak loudly). The USPSTF starts its recommendation process with a systematic review of the evidence. Experts such as those on the USPSTF do us a great favor by examining the evidence underlying preventive care practices from the perspective of populations and patients without disease.
Finally, there is the belief that doing something is always better than doing nothing. Suffice it to say that isn’t true. But doctors, patients and people have a hard time with it. It is tiresome to keep hearing that a common bad disease is sufficient information to justify doing something, even when evidence is absent it works, or even worse, when evidence finds harm. “How can you just sit there doing nothing?”
So what should we do?
Despite complaints about evidence-based medicine, I have yet to hear good arguments about why we should ignore high quality evidence or not be explicit when there is an absence of evidence. And like democracy, evidence-based medicine may not be perfect but it is the best we have. Basing clinical practice primarily on pathophysiology, belief and the most recent bad outcome is not a viable alternative.
But while evidence can be very informative, we have a long way to go towards getting it understood and easily used. We need to communicate the evidence accurately and dispassionately to patients in ways that it is accessible to them (which may vary by patient) and at times when they can be receptive.
At age 40, a woman’s chance of dying from breast cancer is 3% (5-year risk if no risk factors is 0.4%, and up to 6% or more if risk factors are present). http://bit.ly/pi2cNq Screening during ages 40-49 reduces that chance by 15% (95% credible interval 1%-27%), to 2.55% (a 0.45% decrease and up to 56% of women will experience a false positive. Because not everyone adheres to screening, the number needed to screen to prevent a breast cancer death even in clinical trials is 1904 (see USPSTF evidence report; google it). A model for communicating this type of information visually with patients can be found here http://bit.ly/pyqqbR
For prostate cancer, the lifetime risk of dying from it is 2.8%, most after age 75. The benefit of screening remains uncertain but one trial puts it at a 0.7% absolute risk reduction for prostate cancer specific mortality (eg to 2.1%); 80% of PSA tests are false positives (and that doesn’t consider the fact that most actual cancers wont lead to death), 20% will get a biopsy (in 10 years of screening), and 20-30% of men treated for prostate cancer with surgery or radiation will have incontinence or erectile dysfunction.
We also need to offer patients our best medical judgment based on that evidence, taking into account what we know about them—best done by a clinician who has comprehensive knowledge about the patient and is in a longitudinal trusting relationship with them. Easier said than done, I know.
“OK, OK. Whatever,” you might say, “but what will you do?” Hopefully you don’t really care what I would do, at least not as a guide for your practice. But, I’ll tell anyway.
Some of my patients want me to prove they don’t have disease. I tell them I cant do that but they know there are tests that can detect diseases. These patients often think that when I send a blood test, I am checking them for “everything.” I will continue to explain to them that it doesn’t work that way, but in the end, so long as they understand the consequences of testing, I will order the mammogram for the 40-year-old. Prostate specific antigen testing I will reserve for those who are otherwise un-persuaded after I inform them the test likely causes more harm than good and is not recommended, and they request and consent to testing; but I can still order it in those rare cases with a good conscience and consider it good medical practice because I know some cancers will be detected and cured only as a result of testing, even if the odds are strongly against it being the case for this one individual.
I have other patients who say “que sera, sera” or “if it ain’t broke, don’t fix it.” They are not convinced that screening is worth it (after being presented with data in an understandable way). Respecting their values and autonomy, I wont test them.
The patient in the middle ground is the most difficult and perhaps most common. For prostate cancer I will follow the USPSTF guidance against screening. But I will provide numerical information to patients when they are interested. For breast cancer, I will have a low threshold for offering screening to women age 40-49 years as long as they understand the 50% or so chance of false positives (and attendant anxiety, repeat imaging, biopsy and other procedures unnecessary only in retrospect) and still deem it worthwhile to them.
This past week the USPSTF released its recommendation that cervical cancer screening be started later (age 21) and be done every three years (or not at all after smears are negative 3 times in a row). There is another presidential debate today in the US; probably this will come up. It’s going to be another energizing week…