The Present and Future State of Breast Cancer Screening
An array of high-tech detection techniques and devices is on the scientific horizon.
By Dulce Zamora
Reviewed By Michael Smith
Cora's doctor found a tiny growth in her right breast when she was 55 years old. To determine whether it was cancer, he inserted a small tube inside her nipple to extract cells for study under a microscope.
The results were inadequate so he asked her to come in for another visit. This time, she was given anesthesia so he could surgically remove the suspicious tissue for examination.
Much to Cora's relief, the lump turned out to be benign, but recalling the whole process is enough to make the now 60-year-old tax auditor cringe.
"The nipple thing was very painful," she says, associating the unpleasant experience with other cancer-screening procedures she considers torturous, such as the mammogram, which involves placing one breast at a time on a cold device then flattened for filming.
Still, to this day, Cora, much like many of her peers, diligently subjects herself to such tests. Why?
Yet medical visionaries are hoping women won't have to be martyrs for long. While mammography is still widely regarded as the gold standard for detecting malignancies, an array of new or improved technologies is now on the horizon -- using magnets, electricity, sound waves, and cellular biology as screening tools.
Some methods promise to make breast cancer screening more comfortable for women. A number pledge better accuracy, or less chance of an inaccurate report. Still others are whispered to be borne out of entrepreneurial motivations.
There are doctors who dream of someday being able to take a simple blood test to determine whether a woman definitely has breast cancer, or will develop it in the future. Thus, in determining the threat, they hope to be able to tell a woman when she likely will have breast cancer, and what can be done about it.
But word on the scientific street is that such diagnostic wizardry will not be available anytime soon. Experts can only be optimistic that the present crop of newly improved or experimental screening techniques will improve what's out there now.
Improving familiar devices
Recently, the accuracy of mammograms has been called into question and experts don't even agree on the appropriate use of this test -- some recommend starting routine mammograms at 40 while others say 50. So researchers are furiously looking for a better approach to diagnosing breast cancer than the standard X-ray mammogram.
Digital mammography, which takes the X-ray image on computer rather than on film, is creeping into the breast-imaging landscape. There are now about 300 such units in use around the country, according to the American Cancer Society (ACS).
The instrument "offers enormous potential" because the pictures can be manipulated, says the ACS director of cancer screening, Robert A. Smith, PhD.
Much like digital photographs currently taken by consumer digital cameras, breast images taken by digital mammography can be magnified, and the resolution can be adjusted to get a clearer picture.
However, the gadgets are not known to be more successful in finding cancers than their conventional counterparts, and the cost of each machine tends to be prohibitive.
Smith says the digital imaging technology could especially improve with better programming of computer-aided detection (CAD) devices, which are now used by some labs to analyze standard mammograms and act as second-opinion readers for radiologists.
Early tests show CAD can help point out cancers otherwise missed by experts. Yet there is an ongoing debate about whether a machine can sufficiently replace a second radiologist in reviewing test results.
Medical experts who want to evaluate problems first found during a mammogram or a physical exam often turn to ultrasound technology. An ultrasound device releases sound waves into the body, and creates a picture of the breast from the bouncing back of the waves. The idea is that sound echoes differently of off masses of various consistencies, such as fluid-filled cysts, solid tumors, or normal tissue.
Ultrasound has been around for decades, but improvements to the technology promise to make it more helpful in looking for cancer. One advance of note is still in the experimental stages: an ultrasound that takes 3-D images of the breast as opposed to 2-D ones.
Another breast detection technique that scientists have gradually enhanced over the years is magnetic resonance imaging (MRI). In this method, a large magnet, radio waves, and a computer work together to produce what experts consider a very clear, cross-sectional picture of the breast. Furthermore, experts can examine specific areas by injecting a dye in the veins, which collects in problematic tissues, making them more visible in the MRI picture.
Similar schemes are now under investigation, such as magnetic resonance elastography (MRE), which draws an image of the breast tissue based on the way it responds to vibration.
Toward a better image (of breasts)
Many methods to check for breast cancer are still experimental right now. Often, women at high risk of developing the disease turn to clinical trials of these imaging devices in an effort to ease their concerns.
Some of these experimental methods are:
Positron emission tomography (PET): This technology makes use of the notion that a tumor has a higher metabolism than normal tissue. When a radioactive substance is injected into a patient's vein, it travels to rapidly dividing cancerous cells, which have greater nutrient needs. Ideally, a PET scanner would detect the activity and produce an image of it.
Ductal lavage and ductoscopy: The idea behind these two methods is that certain cancers begin in the milk ducts of the breasts. In ductal lavage, a catheter is inserted through the nipple and into the milk ducts. A saline solution is emptied into the ducts, and then withdrawn. Then the cells washed out from the ducts are checked under a microscope.
In ductoscopy, a catheter with a light at the tip is inserted through the nipple into the ducts and a dye is injected. The dye outlines the shape of the duct and an X-ray ideally shows whether there is an abnormal growth in the area.
Electrical impedance spectral imaging (EIS): Low-frequency electrical currents are applied to the breast, and an image is formed based on the theory that normal tissue and cancerous masses conduct electricity in different ways.
Microwave imaging spectroscopy (MIS): An MIS device uses microwave energy that is similar to cell phone frequencies (but at a much lower level). The technique is particularly sensitive to water, and can detect areas where there is more of it. Tumors are thought to have more water and blood than regular tissue.
Near infrared (NIR) spectral imaging: This laser method creates an image based on the idea that infrared light is sensitive to blood.
Researchers at Dartmouth College in New Hampshire are currently studying the effectiveness of the NIR, MIS, EIS, and MRE in detecting breast cancer. If one or two of the methods are found to be more promising, it's possible that scientists could integrate technologies into a single technique.
"We're excited about the possibilities, but there's a lot to be worked out," says Keith Paulsen, PhD, principal investigator of Dartmouth's Breast Imaging Project.
The team has not yet begun clinical trials, but hopes to do so in the next couple of months.
Looking into a biological crystal ball
Several studies are currently looking into the possibility of diagnosing breast cancer at the cellular level. The National Cancer Institute alone has funded research into at least a half-dozen tests that involve studying typical and irregular proteins, molecules, genes, and other biological matter.
Researchers hope these investigations could someday identify a point when biological substances become cancerous, and lead to development of methods for detecting warning signals.
The technology to screen for genetic mutations is already available, but it is recommended only for women who have reason to believe they are at high risk for developing the disease, such as a strong family history.
In the early 1990s, it was found that women with certain mutated genes -- BRCA1 and BRCA2 -- tend to have a 50 to 85% risk of developing breast cancer.
Since then, the issue of genetic testing has been controversial. Some people say the presence of the mutated gene does not necessarily mean a woman will develop breast cancer, so a positive result could cause unwarranted concern. Plus, overall, these genes account for few cases of breast cancer. Also, there is fear that insurance companies and employers could discriminate against women who have the mutation.
Women who do decide to go through with this test are advised to undergo genetic counseling to help them deal with the information, and to determine a possible cause of action or inaction.
Judy Garber, MD, director of cancer risk and prevention at the Dana-Farber Cancer Institute, says in the future, genetic information and counseling could be more useful with better technology for early detection and prevention.
As an example, she says, "Instead of deciding at [age] 30 to have your breasts removed because you might get breast cancer sometime in the next 50 years, maybe you could wait until you're 60, or you've had your children, and you've gone through your life."
Originally published Sept. 30, 2002
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Last Editorial Review: 1/31/2005 4:46:39 AM
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