Routine mammograms: evil, necessary, or both?

Radiation oncologist Eileen Rakovitch on the latest confusion over breast cancer screenings

Last week, the Canadian Task Force on Preventive Health Care issued new breast cancer-screening guidelines that have raised questions and stoked debate. The task force recommended women under 50 who are not at high risk of breast cancer forego routine mammograms. It also recommended that the interval time between mammograms for women aged 50 to 69 be extended from every one to two years to every two to three years—unless their doctors suggest otherwise. And, contrary to what women have been told for decades, it concluded women should no longer conduct regular breast self-examinations.

To sort through the confusion, Anne Kingston spoke with Eileen Rakovitch, a radiation oncologist and chair of the breast cancer program at Toronto’s Sunnybrook hospital.

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Q: It seems this debate never ends. Let’s start with mammograms. Radiologists in the U.S. and Canada have disagreed on this in the past: in the U.S., the recommendation is that women over age 40 should have regular mammograms; in Canada, the thinking has been that women at average risk should begin screening at age 50.

A: There are experts here who believe that screening should start at 40 as well. It’s still a debated issue in Canada. I appreciate that this has lead to a lot of confusion—and it’s very clear why that would be after reading the [task force] recommendations.

People have to understand this is one set of recommendations; it is not a consensus statement from all experts in breast cancer screening or treatment. It has to be taken in context. There are many expert researchers and radiologists and scientists who disagree with these recommendations, and they’ve also been rejected by groups such the American Cancer Society and the Canadian Breast Cancer Foundation. So I think it’s very important for women—and family physicians guiding and advising women—to understand that it’s not universally accepted.

Q: So let’s begin with what the experts agree on. 

A: What we do know is that in the last two decades there has been a decrease in deaths due to breast cancer. Statistics show that. There is also an understanding that the reason we see a decline in breast cancer mortality is due to screening, early detection of breast cancers that are more treatable and more curable at the stage they are diagnosed like DCIS [ductal carcinoma in situ], and due to improvements in treatment. The task force also notes in its recommendation that screening women in their 40s reduces breast cancer mortality. They note a number of 15 per cent. The precise amount that it actually reduces breast cancer mortality can be debated. But they do not actually say in their report that screening women in their 40s does not lead to a reduction in breast cancer mortality. What they do say is that the relative value of that reduction does not warrant routine screening. And therein lies the debate.

Q: Where do you stand on this?

A: Well, I’m a woman in my 40s and I’m going to continue to have [regular mammography] screening. When you read through the full report it actually says that screening mammography reduces breast cancer mortality in women between the age of 40 and 49 and that clinicians should discuss the pros and cons with women. That’s part of the recommendation even though the bullet point is ‘do not recommend routine screening.’ If you actually read the text that that statement is in there. And I agree with that statement. My concern is that a physician will take the bullet point and say ‘No you do not need a mammogram.’

Q: We routinely hear of women in their 40s without a family history of breast cancer who caught a breast cancer early through a mammogram. Is that your experience?

A: Absolutely. I have many women in my practice who are in their 40s who have had mammographically detected invasive breast cancer and have had treatment. There are also many young women with breast cancer;  we have gone on to develop Pynk, a dedicated program for young women with breast cancer. Women need to be informed of the pros and cons. My feeling about these recommendations is that we do not take away the choice of women or the ability of women to be appropriately informed and make those choices with their physicians.

Q: The task force has been criticized for ignoring scientific data from studies using current technology that point to a 25 per cent to 30 per cent reduction in mortality through screening.

A: All of these recommendations (and the note that mammography does not lead to a sufficiently large reduction in breast cancer mortality in younger women) were based on the techniques of mammograms that for the most part are outdated today. These are studies done decades ago using film mammography, and it’s a very different quality image from what we see today. None of these studies included evaluations of digital mammography which have been shown to be more sensitive, particularly for younger women under 50—and which expose women to lower doses of radiation than the older techniques. So it isn’t directly applicable to the effect of screening by today’s standards. And we do not know the impact of digital mammography on all of these end points including mortality. Digital mammography deals with density, is more sensitive than film and exposes women to lower doses of radiation.

Q: The conventional thinking on mammography is that it’s a more useful tool on older, less dense breasts, i.e., in women over 50.

A: Yes, it is more sensitive in picking up cancers in older women because fatty tissues look black on a mammogram and so it’s easier to detect calcifications which are white or tumour mass which may be white on a black background. When a woman has very dense breasts the background is white; so identifying white on white obviously becomes more difficult. The advantage with digital mammography is that the radiologist can alter that background contrast making it easier to pick up lesions in dense breasts, and that’s the issue for younger women—that they’re more likely to have dense breasts.

Q: The study focuses on the risks of “over-diagnosis” of false positives and “over- treatment” in terms of unnecessary procedures. How much of that has to do with the fact that technology now is able to detect abnormalities that wouldn’t have been seen decades ago—and wouldn’t have affected health or morality?

A: In terms of technology, better imaging allows for a finer image. But, although very important, mortality from breast cancer is not the only end point from a clinical point of view. The diagnosis of invasive breast cancer has significant impact—psychological impact—and these women will get treatment: chemotheraphy and long-term morbidities from treatment.

What we do know is that a greater proportion of cancers that are picked up through mammographic screening are represented by DCIS, a non-invasive form of breast cancer. And we do know that some women with DCIS will go on to develop an invasive cancer. And that by detecting and treating it early you’re preventing some women from having a diagnosis of invasive cancer or experiencing the long-term sequella of treatments. That is also an important factor to consider when weighing the pros and cons of screening. It’s not only about breast cancer mortality.

Q: So what is the advantage of regular mammograms for women over 40? 

A: The pros of screening mammography include the potential to diagnose breast cancer at an earlier stage, to diagnose breast cancer at a non-invasive stage like DCIS—that if it’s there can require less aggressive treatment and lead to a reduction of breast cancer mortality.

Q: And the risks?

A: No test in medicine is perfect. There will be false positives. Some women will have a lesion that is indeterminate and require additional investigation such as an ultrasound or an MRI. Or require a biopsy and maybe even surgical excision for something that is ultimately benign. And through that process there is anxiety and distress. But women can choose and weigh whether the benefits for them warrant the potential risks and that is another main issue of consensus: do we take away the role of women and their own physician to weigh the pro and cons on their own?

In this task force recommendation it is written that the relative value of a 15 per cent reduction in mortality has low value and the potential downside such as additional biopsies have high value. Those are preferences that may not apply to any given individual. Those are assumptions that were made by this task force. All I’m saying from a clinician’s point of view is that I do not think that that decision and the ability to weigh the pros and cons should be taken away from women—unless the bottom line is purely one of cost savings.

Q: That’s an interesting point. A lot of people are asking whether the recommendation to scale-back screening is a cost-savings measure—of the cost of mammograms and other procedures.

A: It’s difficult for me to comment on the extent to which economics are a factor in these recommendations because I do not know that.

Q: These recommendations do not pertain to women who have a higher than average risk of developing cancer in their lifetime, though the rules surrounding this is also is confusing. High risk includes having a mother or sister who has had breast cancer, a history of breast biopsy, and “dense breasts.” But how do women know it they have “dense breasts”?

A: On a routine mammogram the radiologist looks at the appearance of the breast tissue; there are measures to measure if a woman has dense breasts, there are categories.

Q: So it’s a Catch-22. A woman under 50 needs a mammogram to find out if she’s part of a category that should have a mammogram?

A: That’s exactly right.

Q: What is your position on the task force recommendation that the mammogram screening interval for women over age 50 be extended from one to two years to two to three years. 

A: That recommendation isn’t based on any scientific evidence. There is no data or trials showing that every three years is as good as one to two years.

Q: So what would it be based on?

A: We don’t know. Many of the experts in screening I’ve discussed this with say there’s no scientific basis to suggest every three years is as good as shorter intervals.

Q: Let’s move on to self-examination. The task force says “asymptomatic” women don’t need regular self-exams. But isn’t one the first way to detect a symptom—especially if you don’t get mammograms—through self-examination?

A: Yes. Again it’s important for women and physicians to understand these recommendations are not universally accepted by all experts. Women need to be informed of what they are looking for because if they’re not clear they may seek excess medical attention, have anxiety and lead to unnecessary investigation. I agree with that. But I don’t agree that women can’t be informed about how to do a proper exam and what to look for. And I think from a practical point of view and as a physician who sees many of these women, what are we to tell women in their 40s if we’re saying don’t do mammograms, don’t examine your breasts? Women are concerned about getting breast cancer.  I don’t think we should be telling women do nothing and hope for the best.

Q: So what do you say to women regarding self-examinations?

A: I strongly advocate that women be informed and are able to weigh the pros and cons, so they feel involved in their own sense of well being. For the most part women are looking for changes in their breasts; they need know what their normal breast architecture is and know a new lump or growing lump that wasn’t there before. The cost of that might be doing unnecessary investigation. And many women may choose not to have screening or self-examination. My view is we shouldn’t remove that choice and the ability to be involved in the conversation.

Q: Women under 40 are off the screening radar. Now they’re getting a mixed message regarding regular self-exams. What would you say to them?

A: There’s no evidence teenagers and women in their 20s need screening—unless they’re deemed to be at very high risk—say, someone who had radiation treatment for a childhood cancer. But again breast health is about awareness and being self-informed. And I don’t know if many women in their 20s even know if they have a strong family history of breast cancer. I have seen women diagnosed in their 40s and only then have they questioned their own family history—and some of them are found to have say a genetic-hereditary form of breast cancer.

Younger women should be aware of what’s normal for them. And if there is something that has developed—a new lump that is growing—then they should seek medical attention.  They should ask simple questions about their family history of breast cancer, of ovarian cancer, and depending on their ethnicity and own family history, they may be at risk. There are questions they can ask their family physician. At Sunnybrook, we have a high-risk clinic where women can be assessed; they can undergo genetic counseling.

That said, we don’t want women to be overly fearful because the average women will not develop breast cancer in her lifetime. But that doesn’t mean they shouldn’t be informed about the signs of breast cancer because some young women do get breast cancer. And it’s very often it’s missed or detected at a later stage because there isn’t that connection that women in their 20s get cancer—and I have women in their 20s who have invasive breast cancer.

Q: Is there any way out of this thicket of confusion over screening?

A: We need to move forward. We need to do better—in improving imaging, understanding the role of MRI in screening and understanding which cancers need treatment. We need to identify the clinical factors, the pathological factors, the molecular factors associated with high-risk women so those are the women who undergo treatment and we avoid the unnecessary treatment. That’s how we’ll reduce over-diagnosis and over-treatment. I don’t think that dropping screening is the way we move forward.