Two other commonly used imaging techniques—magnetic resonance imaging (MRI) and ultrasound—often supplement mammography to detect breast cancer but are not yet reliable enough to be used by themselves for screening. MRI uses magnetism and radio waves to measure differences in the water content of tissue, which provides more detail about differences in the composition of breast tissue than do x-rays. But because a benign cyst often looks like a tumor on an MRI, screening with MRI also increases the rate of false positives. For that reason, the American Cancer Society recommends annual MRI screenings only in women with a strong family history of breast or ovarian cancer. In addition, breast MRIs are too expensive for routine use in the general population, running $2,000 to $6,000 a test compared with a few hundred dollars for a mammogram.
Ultrasound relies on high-frequency sound waves to characterize the internal structures of the breast. Unlike MRI, it can determine if a lump is a harmless, fluid-filled cyst. But its images cannot distinguish malignant tumors from benign growths filled with harmless breast tissue. It thus gives more false negatives than mammography does, which is why it is less than ideal as a stand-alone method for initial screening.
Fresh Ideas
Researchers, in their quest for better solutions, are experimenting with new twists on an age-old method: feeling for lumps. Tumors are stiffer than healthy breast tissue—which is why they feel different. The problem with waiting until a tumor has grown large enough to be felt, however, is that the delay increases the odds that the cancer will have spread by the time it is diagnosed. The goal is to create ways of detecting that stiffness while a tumor is still too small to be felt by human hands.
One method for measuring such stiffness depends on a combination of low-frequency sound waves and MRI. Dubbed magnetic resonance elastography, the technique was first developed more than a decade ago by Richard Ehman, a radiologist at the Mayo Clinic. Currently applied to the diagnosis of nonmalignant liver diseases, the approach is now being tested on breast tumors. Patients are scanned in an MRI while sound waves with a frequency of 60 hertz pass through plastic tubes to the breasts. The MRI picks up tiny variations in how tissue is moved by the sound waves. Ehman says his team has gotten pretty good at distinguishing between normal and malignant breast tissue based on the stiffness revealed by the MRI. But for elastography to work as a population-wide screening tool, the cost of using an MRI would have to be much lower.
Another technique for measuring tissue stiffness dispenses with the expense and claustrophobia of an MRI. Bruce Tromberg, a biomedical engineering professor at the University of California, Irvine, has built a handheld scanner that sends near-infrared light through the skin and into the breasts and then measures how the light energy scatters on its path through the body before it gets reflected back to the scanner. The light photons travel differently through tumors than through normal tissue. The experimental device is being tested in cancer patients to see whether it can be tuned to accurately measure tumor shrinkage in response to therapy. Tromberg hopes, though, that the technology can eventually be refined enough to spot malignancies while they are still microscopic.
A simpler screen, like a blood test, would be ideal. Physicians do have blood tests that detect the recurrence of breast and ovarian cancer, such as by measuring a molecule called CA125, but they are not accurate enough for large-scale screening. Several researchers, however, are tracking chemical markers in the blood and in the breath with the goal of creating screening tools that could someday not just find cancer but also indicate how dangerous it is likely to be.
Emory’s Gabram-Mendola and chemists at the Georgia Institute of Technology have found markers in the breath of 20 breast cancer patients that were not present in the breath of 20 control subjects. The team is not focusing on fully replacing mammography but on saving it to use as a follow-up tool in places where resources are scarce. “There is a huge need to come up with something that can be used in countries where mammography is less available,” says Charlene Bayer, who is leading the effort at Georgia Tech. A breath test performed in a doctor’s office could also have great appeal for the many women in developed countries who shun screening mammograms because of the discomfort and inconvenience.
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5 Comments
Add CommentBeyond Mammograms. Conventional breast cancer screening tests are far from perfect.
Reply | Report Abuse | Link to thisSome, perhaps many, women of any age who are fully informed about the benefits and the harms of mammography may rationally decline mammography screening for breast cancer. The body’s immune system continuously searches out and destroys cancer cells, including breast cancer cells. One third of breast cancers that are detected by mammography would never cause symptoms, let alone death. This over detection by screening is called “over diagnosis.” Over diagnosis, not false positive or false negative mammograms, is the most harmful aspect of all forms of cancer screening, including mammography. If 2000 women are screened by mammography over 10 years, one will have her life prolonged, and 10 others, who would not have otherwise been diagnosed with breast cancer, will have a breast cancer diagnosed and treated unnecessarily. In other words, 1 woman will avoid dying of breast cancer. Ten other healthy women will be treated unnecessarily, 4 of these will have a breast removed, 6 will receive breast conserving therapy, and most will receive radiation therapy.
Detecting breast cancer cells at earlier and earlier stages will not necessarily translate into more overall value for women. Earlier detection will almost certainly increase the amount of over diagnosis. Whether earlier detection will translate into any additional benefit in terms of avoiding death from breast cancer is an open question. A better long term approach to preventing death from breast cancer is more basic research into cancer mechanisms leading to better treatments. After all, if there were a perfect treatment for breast cancer after it became symptomatic, there would be no justification for screening. That would save many women from the harm of over diagnosis. At least half or more of the decline in breast cancer mortality recently can be attributed to better treatments, not to better screening.
For your readers, the bottom line should be: always ask about the harms, as well as the benefits, of any test proffered by the medical profession. Then make an informed choice based on your own personal values. You cannot depend on the medical profession to do this for you, because we (I am a physician) almost always emphasize the benefits and discount the harms of what we are selling. Caveat emptor.
Thanks to the Dr. making the comment below. I decline mammograms because of the reasons she/he states. In addition, I am guessing mammograms are riskier for some women than others because of the potential damage to tissue from "mashing the breasts" into the clamps to get the image. I bruise very easily, and am aware that tissue damage can contribute to cancer. So it doesn't seem like a good idea to use a test that is harsh on the breast tissue, unless there is really good evidence of benefit. The author of this article doesn't mention THERMOGRAMS at all. My understanding is that this method of detection, while not perfect, is overall better than mammograms as a screening tool, if done by a well-trained person. Thermograms are completely non-invasive, since they measure the heat radiating from the body. Cancer tissue is "hotter" since it requires a larger blood supply than normal healthy tissue. My understanding is that thermograms are used more widely in Europe, but not very well known in the US at this time. So I would like to see this method included in the discussion. I get thermograms regularly.
Reply | Report Abuse | Link to thisI am a radiologist who spends 90% of his time in breast imaging. There are some points on which I would disagree with the author. She states that biopsies can be disfiguring and can cause problems with later diagnosis. I would agree, if the biopsy were surgical, however, in any modern medical practice the standard is needle biopsy, which is certainly not disfiguring, and cannot cause difficulty in later diagnosis. Further, they are not particularly uncomfortable. Most patients agree that they are not nearly as uncomfortable as a dental procedure.
Reply | Report Abuse | Link to thisMRI scans absolutely can tell cysts from solid masses in the breast, but do have difficulty because of overlap between various benign conditions (such as fibroadenomas, or, at times, simply hormone stimulated normal tissue) and cancers. The principle that MR uses is that of increased blood flow to malignant tumors, and this can be seen with other non-malignant pathologies.
Ultrasound can distinguish some forms of benign tumors from cancer, but, like mammography and MR, there is overlap, with some benign tumors resembling cancers. Even with this, though, often with ultrasound we can make a determination that a mass is "highly likely" to be benign. These patients have no further work-up.(Note the hedge: "highly likely". We know from experience that sometime, somewhere a cancer will arise that will resemble benign tissue.)
I think of the imaging work-up of possible cancer as a sorting process: for every 1000 women who come for screening, about 70 will have something sufficiently worrisome to warrant more pictures. 60 of these will be found to be fine, 10 will require biopsy to "be sure". About 3 to 4 of these patients will have cancer, and most of these will be cures. About 1 will not be.
Strikingly absent from the discussion is the fact that the false positive rate can be controlled. If I wanted, I could tomorrow reduce the number of patients I call back for more imaging. However, the statistics of the process are such that by doing so, I will necessarily increase my false negative rate. Our society does not tolerate a false negative. Plaintiffs attorneys enforce this. I have heard it said by colleagues that the cheapest malpractice insurance that one can purchase is to call back a patient for more images. A sad commentary, to be sure, but deadly accurate.
I appreciate the inclusion of other methods that are being developed, but would point out that, inevitably, there will be overlape between malignant and benign with these methods, also.
I urge the publisher to take a look at Deborah Rhodes presentation at TED http://www.ted.com/talks/lang/eng/deborah_rhodes.html
Reply | Report Abuse | Link to thisIt is a HUGE breakthrough in visualization techniques for breast cancer discovery and should be regarded in this article.
In the 1980's I tried to develop with others an AI solution to reading mammograms. It was pretty hopeless, due to a number of reasons. The obvious ones that computers were pretty basic and graphics terrible. But I always had a the overwhelming problem that the exceedingly experienced radiographer who worked with us seemed able to see things that we, as lay people, just could not.(Something I have found in other industries). I just gave up disheartened and moved onto other things.
Reply | Report Abuse | Link to thisBut at a much later (circa 2000) a large amount of reported literature pointed out that London Taxi Drivers brains actually altered physically when learning the complex task of remembering roads in a big city.
Similarly sportsmen practice for days on eye hand co-ordination tasks, presumably not just to muscle hone but to establish learning correction patterns.So that the brain knows how to hit the ball/target.
A quick scout through the literature on mammograms shows some work on people comparing gold standard radiographers with normal clinicians, some of these showed minimal differences, but the samples were all very small and the images did not have artificially added problems.
Is it possible that better training on a large number of high precision computer modified mammograms, each with subtly induced artificial deposits could lead to better diagnosis?
PS I am no longer in this field.