Difference between relative risk & absolute risk
How Tiny Are Benefits From Many Tests And Pills? Researchers Paint A Picture
By Jay Hancock October 12, 2016
Excerpt:
Mammograms are said to cut the risk of dying from breast cancer by as much as 20 percent, which sounds like an invincible argument for regular screening.
Two Maryland researchers want people to question that kind of thinking. They want patients to reexamine the usefulness of cancer exams, cholesterol tests, osteoporosis pills, MRI scans and many other routinely prescribed procedures and medicines.
And they want to convince them with statistics — but don't worry! They promise not to use algebra or spreadsheets. Or even numbers.
Health costs continue to grow much faster than the economy's ability to pay them. Partly as a result, scrutiny of potentially unneeded and harmful treatment has never been more intense.
Nearly three physicians in four surveyed by the American Board of Internal Medicine said unnecessary tests and procedures are a serious problem. The authoritative National Academy of Medicine estimated that 30 percent of all health spending — $750 billion — is wasted on fraud, administration and needless procedures.
But even doctors often don't understand the tradeoffs involved in many tests and medicines, says Dr. Andrew Lazris, a Maryland internist. When they do, they have trouble explaining them to patients.
To change that, Lazris and environmental scientist Erik Rifkin are trying to popularize an intuitive, pictorial way of showing just how few people are helped — and how many are even harmed — by many common procedures.
Health is best discussed in the language of risk and probability, but the $70 billion spent on long-shot government lotteries every year suggests that Americans are a bit challenged in that regard. Behavioral psychologists have confirmed what a French writer observed in the 1600s: "Each believes easily what he fears and what he desires."
Especially about health. Lazris and Rifkin want to give people a more realistic way of evaluating medical hopes and worries.
They ask patients to picture a hall of people getting a test, operation or prescription. Patients might be shocked at how few in the crowded room get any benefit out of the expensive care.
Their "benefit-risk characterization theater" images vividly show the odds, based on solid research. There's a sold-out house of 1,000 playgoers or concertgoers, all getting a particular kind of exam, screen or pill.
Then the curtain falls. Everybody helped by the procedure or prescription gets up and leaves. Often it's only a few people. Sometimes very few. Or nobody.
For breast exams, only one woman in the thousand-person theater receiving mammograms over a lifetime is saved from dying by detecting a cancer before it spreads, according to Lazris' and Rifkin's summary of the research.
At the same time, hundreds of women in that audience will receive test results suggesting they have cancer when they don't — "false positives." Sixty-four get biopsies, which generally involve cells withdrawn through a needle, for nonthreatening lumps.
Ten receive unnecessary treatment including radiation and surgery for lumps that never would have caused a problem.
The theater images show all of that as well, presenting visual demonstrations that the odds of harm, worry or inconvenience caused by the tests are often much higher than the likelihood of benefit.
Drawing conclusions from mammogram studies is contentious. Some reports show greater benefits — as many as five fewer deaths for 1,000 women. For women with a family history of breast cancer, dense breasts and others with higher risks, benefit from screening — perhaps beyond mammograms — is higher than for those with normal risk, researchers say.
But for the average woman the benefit is small by any measure.
Showing all this with theaters "seems like a great idea," said Dr. Zackary Berger, an assistant professor at the Johns Hopkins School of Medicine who studies patient communication. "It seems pretty intuitive, and that's the trick. You want to deliver this information in a way that people can really take in."
Medical decision aids exist online. But doctors may not know about them, Berger said. Even if they do, showing patients requires a computer and a bunch of keystrokes. The theaters are pictures on paper.
What Lazris and Rifkin especially want to combat is the practice of discussing only relative benefits of medical procedures.
Stating that a mammogram lowers mortality risk from breast cancer by 20 percent says nothing about how likely a person is to die of that disease in the first place. Not to mention what the test might cost in pain, harm or hassle.
Cutting risk by 20 percent sounds impressive — until one realizes it might be the difference between five women in 1,000 who don't get mammograms and die of breast cancer and four women in 1,000 who do get mammograms and die of breast cancer anyway. (Mammograms miss lots of deadly cancers, and some tumors prove fatal even with early detection.)
That's not much change in absolute risk. The theater images capture that subtlety.
Other procedures and prescriptions show similarly small benefits.
Continued at link in article title
Comments
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The trouble is that none of us know whether we will be among those who benefit (or not) from any given screening exam.
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More news on the topic of mammography screening:
Mammograms more likely to cause unneeded treatment than to save lives
excerpts:
OCTOBER 12, 2016
A new study offers a reality check to anyone who says a mammogramsaved her life. For every woman in whom mammography detected a breast cancer that was destined to become large and potentially life-threatening — the kind that screening is intended to head off — about four are diagnosed with one that would never have threatened their health. But the surgery, chemotherapy, or radiation that follows such diagnoses can be traumatic, disfiguring, toxic, or even life-shortening even as it's unnecessary.
Prior estimates of how many mammogram-detected cancers are overdiagnoses, meaning they don't need to be treated, have ranged from 0 to 54 percent. The new study published Wednesday in the New England Journal of Medicine, improves on those by using hard data rather than mathematical modeling, and 40 years of it.
The researchers compared records of breast cancers diagnosed in women 40 or older during two periods, 1975 to 1979, before mammography became common, and 2000 to 2002. As you'd want with cancer screening, more small tumors (less than 2 centimeters across) and fewer larger ones are being diagnosed: 36 percent vs. 64 percent in the 1970s and 68 percent vs. 32 percent in the 2000s.
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But mammography is such an emotional topic, said breast surgeon Dr. Deanna Attai of UCLA Health, that shifting the emphasis away from screening will be difficult. "Patients still want to catch breast cancer early," she said. "The idea that no matter when it's diagnosed," including by finding a lump, "you're going to do well has not really caught on with patients after so many years of having early detection drummed into them. Even physicians believe that, and it's a hard mindset to change."
Women who find regular mammograms reassuring should continue to have them, Welch said, keeping in mind that any cancer is more likely to be non-threatening and that the onerous treatment they have might be unnecessary. Women who decline such screenings, he said, "can feel equally good."
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excerpt:
Catch and treat it early, their reasoning went, and you will see one less woman coming in later with a large and aggressive cancer.
But medical researchers have come to recognize that a tumor's genetic make-up, as well as the interaction between tumor and host, are better predictors of its progression than the tumor's size upon discovery. One woman's tumor might reach 2 centimeters and then stop growing for many years. Another's might progress from undetectable to a dangerous 5 centimeters in a matter of months.
It was a new, more complex picture of breast cancer. And it undercut the idea that early detection and early treatment were essential to save lives.
"The mantras, 'All cancers are life-threatening' and 'When in doubt, cut it out,' require revision," Dr. Joann G. Elmore, a physician and epidemiologist at the University of Washington, wrote in an editorial that accompanies the study. The "well intentioned efforts" of doctors, she wrote, are exacting "collateral damage."
As breast imaging became widely available in the early 1980s, physicians told women that catching tumors early, before they could be felt by hand, was key to their survival.
Advocates quickly began pushing for universal screening programs. By the mid-1980s, an American Cancer Society awareness campaign told women over 35, "If you haven't had a mammogram, you need more than your breasts examined."
Click on article title link to read the full article. Thanks!
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I know that we all approach these issues with our own experiences in mind. I try to remain aware of this as I read these studies. However, I've read enough on both sides to know that many of the studies on which the false-positive numbers are based drew on numbers from sites using much older machines and do not reflect current practice.
I also know that many women who are called back for additional views do not go on to need biopsies and I don't think anyone can argue that an US or spot compression mammogram is particularly invasive or even that uncomfortable. I feel that a lot of the hue and cry over false alarms overstates the harms to women and ignores the very real risks involved in undetected tumors.
I also firmly believe that the additional costs and other harms that result from untreated tumors are largely ignored in these studies - and that it's really all about the expense.
I say this, of course, as one whose tumor was found on a screening exam. While too deep and small for anyone to find who didn't know it was there (including my PCP), it had already spread to my nodes. If I'd waited until it could be readily palpated my treatment would have been much more extensive (and expensive) and the outlook that much iffier. So yes, I'm biased.
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Hopeful, I understand your viewpoint, and I also wonder whether the analysis takes into consideration the value of catching tumors before they are large enough that chemo is necessary. But I also think a lot of treatment is based on the molecular composition of the cancer, not just the size. I think the downsides go beyond the false positives, whether they lead to biopsies or just anxiety, but to the overtreatment of DCIS, which is a growing percentage of what mammograms catch. The majority of those would never turn into IDC, but are treated just as aggressively. It's definitely an issue where ALL the costs and benefits need to be considered, especially when you consider the overall cost. And I guess my view is colored by my grandfather's second wife who faithfully got mammograms every year, but still got diagnosed recently at stage III. Kinda makes me wonder what good all those years of testing did her.
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Fallleaves - I think the discussion of DCIS should be separated out from invasive cancer, myself, although it does seem that many women originally dx with DCIS are found to have invasive components once they have surgery. That situation gives me pause.
I'm sorry about your step-grandmother and am sure she must be wondering the same thing - but at the same time, what if she'd waited the now-recommended two years between mammograms? How much would finding it a year from now have affected her chances of successful treatment?
You're right about the importance of the molecular composition of the tumor as opposed to just the size and that's something recent studies don't seem to reflect. In many ways, it seems that the research is not keeping up with current techniques and knowledge and thus basing recommendations on outdated information.
These are all really tough issues and it seems to me that examining only carefully chosen statistical factors over-simplifies and risks doing a good deal of harm. The discussion needs to go beyond numbers and needs a thoughtful, nuanced approach (in my not-very-humble opinion) and a willingness to admit the possibility of errors in approach, design and intent.
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