cancer screening

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Mammogram? 50 Years Of Data And Decision Aids To Help You Think Through

A mammogram image, with arrow in upper left pointing to cancer

A mammogram image, with arrow in upper left pointing to cancer

Any procedure that involves sandwiching your naked breast between hard glass plates is personal. Very. But it’s becoming ever more clear that getting a mammogram also holds an element of personal decision. Medical authorities put out broad guidelines, but then you and your doctor can customize them, based in part on your own breast cancer risk and preferences.

How? Before we get into that, a paper just out in the Journal of the American Medical Association takes a sweeping look at a half century of mammogram data, and offers this big picture: mammograms do save lives, “but those benefits are not enormous,” said Dr. Nancy Keating of Brigham and Women’s Hospital and Harvard Medical School, the paper’s co-author. While the potential harms — that a woman will undergo cancer treatment for a tumor that never would have actually harmed her — have tended to be underestimated.

Here, Dr. Keating lays out the mammogram numbers that I found most helpful:

“If we take 10,000 women who are at average risk at age 40, over the course of ten years about 190 will be diagnosed with breast cancer. Most of these women will do well and would have done well regardless of screening. About five of those 10,000 women will have their life saved by the mammogram. Another 30 of those women will die regardless of the mammogram because unforutunately some breast cancers are so aggressive that they’re destined to be deadly despite the mammogram.

So there is benefit, five out of 10,000 women have their lives saved, but there are also these harms. One harm is false positives and unnecessary biopsies,: Of 10,000 women, about 6,000 will have at least one false positive. At this point, I say to patients, ‘You should expect that you’ll have some false positives, and don’t worry when they call you back.’ The over-diagnosis harm, we estimate: about 36 of those 190 cancers that were diagnosed could be over-diagnosed, and so those women will be treated — because we can’t currently tell the difference between the cancers we need to worry about and those that might not be so concerning, so we treat them all the same. So those women are then subjected to the harms of treatment without gaining any benefits.

So how to customize? How do you help create your own risk-benefit analysis? I asked the Informed Medical Decisions Foundation for helpful tools, and they suggested three:

The National Cancer Institute’s Breast Cancer Risk Assessment Tool

Public Health Agency of Canada Mammography Decision Aid

Healthwise

And for a bit more background, Dr. Keating discussed mammogram issues with co-host Anthony Brooks on Radio Boston, including these highlights:

On the questions Dr. Keating sought to answer in her review: Continue reading

The Latest Piece In The Mammogram Puzzle

It’s just hard to wrap your head around. Cancer screening tests — mammograms, PSA levels, colonoscopies — check for early tumors. Catching cancer earlier is better than later. And yet some research suggests that screening — at least for breast and prostate cancer — may be of dubious worth, because it catches many cancers that would never have posed a danger.

The latest salvo on this controversial topic came last week from Dartmouth’s Dr. H. Gilbert Welch, a leading voice on the problem of overdiagnosis, in a New England Journal of Medicine study and an op-ed in The New York Times. He sums up his findings on three decades of mammogram screening in the Times:

…More than a million women who were told they had early stage cancer — most of whom underwent surgery, chemotherapy or radiation — for a “cancer” that was never going to make them sick. Although it’s impossible to know which women these are, that’s some pretty serious harm.

But even more damaging is what these data suggest about the benefit of screening. If it does not advance the time of diagnosis of late-stage cancer, it won’t reduce mortality. In fact, we found no change in the number of women with life-threatening metastatic breast cancer.

Have lingering questions? Tune in to Radio Boston today a little after 3 p.m. for a discussion of the issue that will include a chance to call in. And it may help to view the video above, in which Dr. Welch explains his findings.

Analyzing Those Widespread Feelings Of ‘Hands Off My PSA Test’

(ABC News on Youtube)

I remember my own natural instincts about cancer screening before a friend in public health set me straight about false positives and other possible harms. I figured the more mammograms I got, the better, right? Same with tests for prostate specific antigen, or PSA, in men, no? The test can save your life. What could be bad?

A lot, of course, including potentially terrible complications from prostate surgery. And earlier this week, a federal panel issued final recommendations against routine prostate screening for healthy men. But the panel’s calculations that the tests do more harm than good have failed to convince many who reason as I used to, that catching cancer early must save lives.

In a paper that couldn’t be timelier, this month the journal Psychological Science publishes an analysis of the “uproar” over prostate screenings last October, when the panel issued its initial recommendations leaning in the same anti-PSA direction.

The Psychological Science paper identifies four psychological factors that “can help explain the furor that followed the release of the task force’s report.” They are:

• The persuasive power of anecdotal (as opposed to statistical) evidence

• The influence of personal experience

• The improper evaluation of data

• The influence of low base rates on the efficacy of screening tests.

The authors, from Ohio State University and The Max Planck Institute for Human Development in Berlin, suggest that the reaction might be different if the panel’s calculations were better explained: “Augmenting statistics with fact boxes or pictographs might help such committees communicate more effectively with the public and with the U.S. Congress.”

I’m all for better explanations. I also can’t help thinking that these psychological factors cannot apply to the experts whose opposition to the anti-PSA recommendations is quoted in this NPR story and in this previous CommonHealth post.

Putting potential arguments aside, the paper offers a wonderfully vivid explanation of public attitudes by presenting the thought experiment of a thousand older men in an auditorium:

Consider two auditoriums, each of which contains 1,000 men age 50 or older. Auditorium “Screened” contains 1,000 men who have had a PSA screening test. Auditorium “Not Screened” contains 1,000 men who have not had such a test. About 8 men from each auditorium will die from prostate cancer in the next 10 years. A very important conclusion to be drawn from these numbers is that screening does not decrease prostate-cancer mortality. How can this be, given that so many men claim to have been saved by a PSA test? Continue reading

Oh, Joy! The Prospect Of Laxative-Free Colonoscopies

(ex_magician/flickr)

Even now, weeks after my first colonoscopy, certain tastes and smells still trigger odd sensory flashbacks to the gallon of salty-swampy laxative liquid I had to glug to clean out my intestines before the procedure.

The taste didn’t seem so bad at first. I scoffed at all the whiners who have made the nastiness of colonoscopy prep so legendary. But near the end of the gallon, I found myself gagging and forced to suck on lollipops to help the swallowing along. Not that I’d ever skip the test. Colon cancer is too common and deadly, killing 50,000 Americans a year, and the effectiveness data on colonoscopies look good. Still, I couldn’t help wondering aloud: Does it really, truly have to be like this?

So even though the prospect of a laxative-free colonoscopy is years away, I can make no pretense of journalistic objectivity. I’m overjoyed to share this news: A new study out of Massachusetts General Hospital, following about 600 patients, suggests that a colonoscopy without the noxious preliminaries is feasible.

The point isn’t just to make life easier for people getting colonoscopies. It’s to help persuade them to get the test in the first place.

I did my due diligence: I asked the study’s leader, Dr. Michael Zalis, director of CT Colonography in the hospital’s imaging department, whether any potential financial conflicts needed to be disclosed — a start-up to develop laxative-free colonoscopies, that kind of thing? But no, no such disclosures, he said. The study was funded by the American Cancer Society, General Electric and the National Institutes of Health. Good enough — please sign me up for ten years from now.

A bit of background: Medical innovators had already invented the “virtual colonoscopy,” in which a patient’s innards are inspected using an abdominal CT scan rather than by inserting a long fiber-optic tube with a camera and a light on the end. But the patient still has to go through the colon-cleansing prep. The new study, just out in the May 15 Annals of Internal Medicine, takes the “virtual” one step farther: it uses software and a special contrast agent to make the colon cleanse virtual as well.

The point isn’t just to make life easier for people getting colonoscopies; It’s to help persuade them to get the test in the first place. Only about half of adults follow the recommendations for getting tested — which include universal testing for people over 50 — and surveys find that the nastiness of the prep is part of the problem.

Let me cut to the chase: If all goes well, I asked Dr. Zalis, how soon might the virtual cleansing be available? Conservatively speaking, he said, at least one more study is needed to confirm his team’s results, and that will probably take at least three years. Continue reading

Breast Tumors, Like Guns In Luggage, Missed Because They're Rare

A mammogram image, with arrow in upper left pointing to cancer

We already knew this about guns and knives hidden in baggage. Now it seems the same important insight applies to cancers hidden in breasts: When the target of a visual search — like a weapon or a tumor — occurs only rarely, we’re far likelier to miss it than if it were much more common.

Jeremy Wolfe, director of the Visual Attention Lab at Brigham and Women’s Hospital, uses this pithy phrase for the problem: “If you don’t find it often, you often don’t find it.”

And a problem it is, from airport security to pap smears. Growing research suggests that because some of the perils we most want to seek and destroy are extremely rare, we’re naturally ill-suited to the task.

A cognitive scientist and vision expert, Wolfe began applying his lab’s work to airport security in the years after 9/11. Now he has just presented real-world findings on breast cancer at the annual convention of the Radiological Society of North America, a gathering of tens of thousands of medical scanning professionals.

Typically, mammography turns up three or four cases of breast cancer for every 1,000 scans, but misses 20-30% of tumors, Wolfe said. His central finding: As many as half of those misses could be the result of the “behavioral effects of searching for something very rare.”

First, to clarify the point, using an example from Wolfe’s convention talk based on lab experiments:

Imagine you have X-rays of 20 bags with guns and knives in them. Mix them into a stack of 40 X-rays in total, so the “prevalence” of weapons is 50%, one in two. If you were a typical scan-checker in Wolfe’s experiment, you would fail to catch only four or so of those 20 hidden weapons.

Now imagine those same weapon-laden 20 suitcases are mixed in a pile of 1,000 bags, so the prevalence of weapons is a mere 2%. It’s the same 20 bags, but your “miss” rate more than doubles, from missing perhaps four weapons to perhaps eight or nine.

Why? These searches are hard tasks, exhausting for our fallible human eyes and brains. Plus, we have a built-in hesitancy about saying we have found something rare. And when targets are rare, we tend to give up more quickly.

Go look for a zebra

Say I tell you to go out to the streets of Boston and look for a zebra, Wolfe said. Continue reading

Will The Shift Against Cancer Screening Reach Colonoscopies?

Yes! I’m a little overdue for a colonoscopy, and I’d been hoping against hope that maybe the recent pendulum shift on cancer screening might get me off the hook entirely for a while. Debate continues, but lately you can just feel the weight of medical opinion tipping somewhat away from routine cancer screening procedures like PSA tests and mammograms.

So I was thrilled today to see this New York Times “Bloggingheads” debate between John Horgan of Scientific American (on the left, above) and George Johnson of The Cancer Chronicles, on the merits of colonoscopies. I’m not off the hook and neither are you; the colonoscopy guidelines haven’t changed.

But John Horgan cites a recent paper in the British Medical Journal that makes me feel a bit less delinquent. And he says quite ringingly: “Mark my words, we’re going to see a big revision on tests for colon cancer as well in the future. I think this is a major wave that is making its way through medicine right now, where we are — I hope — really beginning to question the value of routine screening of healthy people for cancer and other diseases.”

George Johnson has some excellent ripostes, pointing out that if our use of the testing is flawed, that doesn’t take away from the value of working on ways to “nip in the bud” debilitating diseases like cancer.