by Amy Tuteur, MD
Doctors have understood for some time that it was inevitable. The American Cancer Society has acknowledged that cancer screening has been oversold.
It seems like every day you read in the newspaper that what was standard medical care yesterday is now no longer recommended. Don’t doctors know anything? Well, actually they do. And what seems like paradoxical behavior, no longer recommending aggressive screening for certain cancers, actually represents a more sophisticated understanding of the way in which cancer behaves.
The classic understanding of cancer is that once a cancer forms it will continue to grow steadily until it kills the patient. Cancer was viewed as if it were an infectious disease like syphilis. It starts small and easy to treat, may remain hidden for long periods of time, but eventually spreads to other parts of the body becoming incurable along the way. If cancer did indeed spread like that, the aggressive screening programs would make perfect sense.
But decades of research and clinical experience have led to a more sophisticated understanding of cancer. It has always been known that cancers from different parts of the body behave in very different ways. Ovarian cancer is extremely aggressive, while basal cell cancer of the skin grows very slowly. Breast cancer can and does spread to bones and brain, while colon cancer is most likely to spread only to the liver.
More recently we’ve learned that each cancer can be broken down into different subtypes, some more aggressive than others, and some better treated with one regimen instead of another. For example, breast cancers are now analyzed for the presence of hormone receptors on the outside of the cancer cells. The presence or absence of certain receptors tells us whether specific treatments will be helpful or useless, making it easier to target the cancer with the treatment most likely to work.
We have also learned that some cancers follow the model of an infectious disease like syphilis, starting small and curable and ending up throughout the body and incurable, many do not. Some cancers start small and explode aggressively. Others start small and stay small for decades. This more sophisticated understanding is a direct result of being able to diagnose cancer earlier. We now have a much better and far more nuanced understanding of the natural history of various cancers. It has become apparent that rather than finding all cancer, we need only find cancers that are aggressive and can ignore those that are known to grow very slowly if at all.
What’s the big deal? Isn’t cancer screening beneficial regardless of the natural history of the particular cancer? No, it’s not and therein lies the reason for the American Cancer Society’s call for less screening of certain cancers.
The goal of cancer screening is and has always been to reduce cancer deaths and disability, and therefore, that’s how cancer screening should be judged. By that standard, some forms of screening are total successes. For example, the Pap smear, the screening test for cancer of the cervix, has been an unalloyed bright spot in the war against cancer. The test is inexpensive and reliable, the follow up test to actually diagnose cancer (biopsies of the cervix) is harmless, and very few if any women are treated unnecessarily. Screening for cervical cancer saves many lives and has few long term side effects.
By the same standard, prostate cancer screening has been a terrible disappointment. The PSA blood test, the screening test, is notoriously unreliable. Even more problematic is the fact that many prostate cancers grow extremely slowly and are unlikely to spread. Most problematic is that the treatment has very serious side effects, impotence and incontinence. Screening for prostate cancer with the PSA test (and finding tiny cancers) saves no more lives than screening with a prostate exam (which can find cancers that are somewhat larger) and leaves many men with unnecessary long term side effects.
Whereas every cervical cancer is probably dangerous to the patient and the treatment has few long term side effects in any case (since cervical cancer is most commonly diagnosed in women who have completed childbearing), most prostate cancers are not dangerous to the patient and the treatment is often undertaken unnecessarily. It’s bad enough to endure impotence and incontinence as the side effect of life saving treatment. It is tragic to endure it as the side effect of unnecessary treatment.
Breast cancer is similar to prostate cancer. While frequent mammography is more likely to diagnose cancer, there has not been a corresponding decline in breast cancer deaths. Treating many more women with chemotherapy, lumpectomy and mastectomy has produced very few additional lives saved.
The solution to this conundrum, of course, is to develop more sophisticated screening tests, tests that can discriminate between life threatening cancers and non-life threatening cancers. In the meantime, the existing screening tests should be judged on their ability to save lives, not on their ability to diagnose cancer, since many cancers don’t need to be treated.
Screening everybody for everything and screening them often is a very blunt tool that seemed appropriate when we had an unsophisticated understanding of cancer. Now that our understanding of cancer has deepened, the use of screening tests should reflect our new knowledge.
Simply put, screening tests should be reserved for situations in which they save lives. Dialing back on screening tests is not a step backward, it is a step forward in treating only those who need to be treated and not harming anyone else in the process.
Amy Tuteur is an obstetrician-gynecologist who blogs at The Skeptical OB.
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{ 11 comments }
This is the best explanation of the change in guidelines I have seen so far– thank you. In particular, I have been wondering why pap smears are so much more effective than mammograms (at least at age 40-49), and you directly address that point.
I also want to clarify for readers that the agency that recently changed their mammography recommendations– so that they no longer recommending annual screening for women age 40-49– is the United States Preventive Services Task Force. The American Cancer Society publicly disagreed with this change, although they are de-emphasizing other cancer screening tests.
Less aggressive screening may be better for some yet lethal for others. The devil’s in the details. The danger here is that this panel’s conclusions will inevitably be the rationale for denial of coverage.
Doc99:
“The danger here is that this panel’s conclusions will inevitably be the rationale for denial of coverage.”
But why shouldn’t they deny coverage it doesn’t save many lives?
All screening guidelines are necessarily arbitrary. Though people claim to be concerned about dropping the recommendation for yearly mammograms in women aged 40-49, they aren’t clamoring that the recommendations should be extended to yearly mammograms for women aged 30-39? If people believe, as they claim that they do, that it is worth any amount of money to save one life, they should be insisting on screening for women aged 30-39 since breast cancer can occur in that group, too.
Moreover, there’s nothing special about whole numbers that end in 0. Why not recommend yearly screening women aged 28-39? For that matter, there’s nothing special about yearly intervals. Why aren’t they recommending screening for all women every 6 months instead of every 12 months? Surely we could save a few more lives that way, too
Unless we plan to screen all women all the time, we must make guidelines, and those guidelines will necessarily mean that some women will not have their cancer diagnosed as early as technically possible. That doesn’t mean that we shouldn’t have guidelines. And those guidelines must be determined by what the scientific evidence shows us.
More aggressive screening may be better for some yet lethal for others. The devil’s is in the details.
Excellent explanation.
Doc99 – there are a number of things that USPSTF has “against” recommendation e.g. EKJ for every physical, yet doctors do it all the time and insurance pays for it. In fact there was a study in NEJM a couple of years ago that showed that over 50% of annual physicals include non-recommended tests. There is absolutely no reason to think this recommendations would lead to denial of coverage. What it may lead to is more honest discussions and more people being aware that more screening is not necessarily better.
The task force included no onologists on a panel evaluating screening for cancer. Curious … as is the timing.
Pardon the the typo … oncologists.
“The task force included no oncologists on a panel”
That isn’t a requirement. You don’t need to be an oncologist to analyze the data.
I’m not claiming that there is no room for disagreement. There is no doubt about what the data shows, but there is doubt about how to act on it. My point, though, is that this is not some sort of plot to deny care or deny coverage. This is precisely where the scientific evidence leads.
The greatest strength of medicine is that it changes in response to new information. We have new information. The recommendations changed. That’s what’s supposed to happen.
If we continue going down this road, it is not to far-fetched that the annual physical and primary care physicians will become obsolete since most of what is done at the annual physical is “screening”.
“the Pap smear, the screening test for cancer of the cervix, has been an unalloyed bright spot in the war against cancer. The test is inexpensive and reliable, the follow up test to actually diagnose cancer (biopsies of the cervix) is harmless, and very few if any women are treated unnecessarily. Screening for cervical cancer saves many lives and has few long term side effects”.
I totally disagree with this statement.
The pap smear is an unreliable test that sends many healthy women for biopsies. Biopsies are not things to be taken lightly – they can leave women with psychological problems/pyschosexual issues, infertility, problems during pregnancy and cause pre-term labor. These are things that are well-documented and that is why the guidelines for pap smears have finally been revised – to contain the harm to healthy women.
Writing off these procedures as minor is hard to understand – I doubt many women would agree with you.
The really sad thing is that almost all of these biopsies are unnecessary – only a tiny number of women are actually helped by cervical screening while thousands of women go through the anguish of a false postive and unnecessary biopsies.
Women have been pushed, pressured and coerced into cervical screening, with no risk information and regardless of their risk profile, to their detriment. Doctors have always ignored the need to obtain informed consent.
The risk of this cancer has always been exaggerated and the benefits of the test over-stated…
Sure a few women are helped, but at what cost to healthy women?
Most countries don’t do annual exams and we’re all doing fine…
It’s only in mid-life that we might see the doctor every year for blood work and a BP test.
I think these annual exams lead to excessive testing and over-treatment. I know US women have more pap smears and cervical biopsies than any other women in the world.
An American woman in her 60’s might have had 50+ pap smears by now and probably a biopsy or LEEP….whereas in my country, she’d be offered 5 to 7 tests in total over her lifetime and no routine gyn exams at all.
We have the lowest rates of cervical cancer in the world and send far fewer women for biopsies. (Finland)
Less is definitely more with cancer screening.
Do away with your annual exams and you’ll all be a lot healthier.
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