The tests can be very good at catching small tumors, but may won't progress to become dangerous. By Brenda Goodman
A new study estimates that only 1 in 5 small cancers detected by screening mammograms go on to become larger, life-threatening tumors. The study suggests that the harms of getting regular mammograms maybe substantial. That’s because mammograms seem to be very good at catching small tumors, and the majority of the tumors they catch were never going to go on to become dangerous. The problem is that doctors don’t have a good way to tell which small tumors will go on to become life-threatening and which ones will not. Therefore, every tumor that’s found gets treated, even if it didn’t need to be. The result is that some women will suffer more from diagnosis and treatment of their disease than they would have from the cancer. The new study was led by H. Gilbert Welch, MD, Professor of Community and Family Medicine at Dartmouth Institute in Lebanon, NH. Welch has spent his career studying overdiagnosis — the diagnosis of a disease that would never actually make a person sick. It’s a side effect of screening, and something that can be confusing for patients. We asked Welch and another expert, Joann Elmore, MD, a professor of medicine and an investigator with the Fred Hutchinson Cancer Research Center in Seattle, to explain what overdiagnosis means and what patients need to understand about it before they get tests like mammograms. WebMD: Your study has found that since mammograms first started being widely used in the 1980s, there have been many more small tumors found by these tests. The number of large tumors—the scary ones—have also gone down, but only by a little bit compared to the big increase in small breast cancers. What does that mean? Welch: The idea is you find a small tumor, and if all tumors were destined to progress, you would expect to have one less large tumor, because you’d found that tumor earlier. WebMD: You found it doesn’t work out that way. Welch: No. That’s because all tumors are not alike. Think of different types of cancers as birds, rabbits and turtles. You can think of mammograms like a fence. The goal is to try to fence in these animals to keep them from getting away. The birds are the fastest growing cancers. These are the ones that have already spread by the time they are detectable. Screening can’t help with the birds. Then there are the rabbits. You can catch those if you’ve got enough fences. That’s where screening can potentially exert its best effect, against the more slowly progressive cancers. Then there are the turtles. These are the cancers that aren’t going anywhere anyway. You don’t need any fences. The unfortunate reality is that screening is really good at catching turtles, and that leads to all the problems of overdiagnosis and over treatment. WebMD: What are some of those problems? Elmore: I see many of my patients struggle to pay for the diagnostic workups. Depending on how much health coverage you have, these can be over $ 5,000. It’s very expensive getting these subsequent diagnostic mammograms and ultrasounds and biopsies. Then there’s the fear and anxiety that you’re seriously ill when maybe you aren’t, and the treatments for breast cancer have significant side effects. WebMD: How do you talk to your patients about mammograms? Elmore: I really work on explaining the risk. Women are afraid of breast cancer, and rightly so. I’m a woman. But women have a heightened perception of their risk. Women hear this 1 in 8 number and they think that’s 1 in 8 women will die this year. It’s the risk of being diagnosed at some time in their entire life. Breast cancer is more common in your 80s. We hear this 1 in 8 number and it alters a lot of women’s perceptions and makes them feel that they are at higher risk. And they also think that mammograms are going to save their life. Whereas, we now know that there are a lot of wonderful improvements with treatment, regardless of what stage you’re diagnosed in. I do let women make this choice. I think that’s very important. Some women have very strong feelings and I just want to make certain that they understand what they’re getting into. I also warn women about false positives. That’s a very anxiety-provoking experience. They go and get the mammogram and then they get the telephone call or the letter that says ‘Dear Mrs. Smith, don’t worry, but you might have breast cancer.’ Then it can take them a few weeks to complete the subsequent diagnostic screening. Over a decade of getting mammograms every year, 50% of women will have that experience. So I try to educate my patients before they get to mammography about some of the downstream things that might occur. WebMD: If you go in for a mammogram, and they find something, do you have any way of knowing if it will become cancer? Welch: The answer is that you have some clues—the size and grade, but you don’t have 100 percent knowledge. That’s the conundrum. WebMD: So if you can’t tell, you have to treat it. Elmore: Yes, probably. I would want to treat it. There are a few doctors, there’s a breast surgeon in California, who are giving their patients the option of watchful waiting, especially for the diagnosis of ductal carcinoma in situ (DCIS). WebMD: I think people understand the concept of overdiagnosis in prostate cancer now, the idea that you can detect an early prostate cancer and the man might be able to live with it his whole life. We now have more men who are opting to monitor their cancers with their doctors—watchful waiting—instead of treating it. Do you think people understand that this happens with breast cancer, too? Welch: I think they’re beginning to. I think this is a process. It took a while in prostate cancer. It will take a while in breast cancer. By the way, these two organs aren’t that different. They’re both glands. They respond to hormones. And if you look at autopsies, they harbor a lot of small cancers, in women and men who’ve died from something else. In the breast, you occasionally have small cancers form and then they go away. They ebb and flow. Every once in a while a really bad one happens. The idea of screening was a perfectly reasonable idea, but people didn’t quite expect this secondary problem—that you started finding things that were never going to make a woman sick WebMD: Given the harms of overdiagnosis, what’s the right approach to getting tested? There are a whole menu of options out there now. Start at 40. Start at 50. Get a mammogram every year. Get a mammogram every two years. Is there a recommendation that you like? What’s the right approach? Welch: I understand that. I guess I’m not even comfortable with the word “recommendation.” I always feel like this is such a down discussion. But there’s some really, really good news here. The good news is that deaths from breast cancer have fallen. One of the things we do in this paper is explain how the vast majority of that reflects better treatment, and all women should know that. Our treatments for breast cancer really have gotten better. I think that’s a really important message to get out. Ironically, the better we get at treating a disease, the less important screening becomes. The early detection/screening side, I think it’s really important that women know there are two sides to that story. They’ve only heard and been told about the potential for benefit, and it’s always very dramatic. Lifesaving language. Big effects. And that’s exaggerated. If it exists, it’s a small effect. And there are downsides. The false alarm rate in this country is egregious for a screening test. For half of women to have a false alarm over 10 years, that’s just not good medicine. The overdiagnosis problem, the problem of treating people who would otherwise not be treated, has real implications for how women think about screening. Both the question of whether they want to be screened at all—which I think is a genuine choice—to the question of how aggressively they want to be screened. How early they want to start, how frequently they want to start. And the question of whether they want to consider acting on it. Every few weeks there’s another test that can find more cancer. We all been taught that the best test is the one that finds the most cancer. Women need to understand that’s not the right metric, that maybe we’re already finding too many breast cancers. SOURCE: http://blogs.webmd.com/webmd-interviews/2016/10/how-mammograms-can-cause-harm.html
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