"I continue to be impressed by the service and treatment I receive at WRA. The technologists performing my mammograms have always been courteous, friendly and responsive. They guide you through the entire process, provide specific directions and tell you what to expect. They are very reassuring."
- Denise, Bethesda, MD
Results from one of the largest breast cancer screening studies ever performed are helping clinicians provide better guidance for the appropriate delivery of essential mammography services for women.
The Digital Mammographic Imaging Screening Trial (DMIST) was conducted by the American College of Radiology Imaging Network (ACRIN) and funded by the National Cancer Institute. Results from the study were published in the September 2005 online release of the New England Journal of Medicine. To read the study in its entirety, click here.
Washington Radiology Associates, PC was the only provider in the Washington, DC area to participate in the study, which included nearly 2,000 women from DC, Northern Virginia and Suburban Maryland. According to Dr. Julianne Greenberg, mammography director at WRA and one of 33 Principal Investigators for the study, this important study provides critical data that will be used to determine the best way to deliver mammography services to women who are screened for breast cancer. “At Washington Radiology Associates, we are proud to be a part of this landmark study representing women in our region,” she explained. “The results of the DMIST trail will greatly benefit clinicians and patients. We are confident that it will improve our ability to detect early, curable breast cancer in women.”
Starting in October 2001, DMIST enrolled 49,528 women at 33 sites in the United States and Canada who had no signs of breast cancer. Women in the trial were given both digital and film mammograms. Mammograms were interpreted independently by two different radiologists. Breast cancer status of DMIST participants was determined through available breast biopsy information obtained within 15 months of study entry or through follow-up mammography approximately one year later.
For the general population of women, the study showed no difference between digital and film mammography in detecting breast cancer. However, for certain groups of women, digital mammography detected up to 28% more cancers than standard film mammography. These subgroups of women who benefit from digital mammography are: 1) women under age 50, 2) premenopausal and perimenopausal women, and 3) women with dense breasts. A large percentage of women who undergo screening mammography may fall into one or more of these subgroups. In fact, in the DMIST trial, 65% of women were within at least one of these groups.
There are important differences in the way film versus digital mammograms are acquired. Standard film mammograms are made when x-rays expose a sheet of film, which both captures and displays the image. However, these images cannot be manipulated after they are obtained. Digital mammography works by taking an electronic image of the breast and storing it in a computer, which allows the recorded data to be enhanced, magnified, and manipulated to improve visualization of tissues. This is called “post-processing”. The electronic digital mammogram image also can be printed on film.
At present, only 8 percent of mammography units in the USA are digital systems, although this number is expected to increase in the coming months and years as new digital units are installed. Washington Radiology Associates currently provides digital mammography services at its Bethesda, Maryland office.
Given the results of the DMIST trial, the availability of digital mammography is expected to increase in the future. In the meantime, according to the American College of Radiology, if a woman is due to have her regular screening mammogram, she should not delay having it in order to wait for a digital study. The American College of Radiology recommends yearly screening mammography for all women beginning no later than age 40. Numerous clinical trials have shown that regular screening mammography reduces mortality from breast cancer and will often detect breast cancer when it is very early, so it can be successfully treated.
While most insurance companies cover digital mammography, in the DC area some may not. Always check with your insurance plan to verify coverage before any medical appointment.
(Below is a fact sheet prepared by the American College of Radiology Imaging Network about the DMIST study, which compared the accuracy of digital versus standard film mammography to detect breast cancer.)
The Digital Mammographic Screening Trial (DMIST) showed that, for the entire population of women studied, digital and film mammography had very similar screening accuracy. For certain groups of women, however, digital mammography was more accurate.
Who would benefit from digital screening mammograms?
Women who fit ANY of these three categories:
Who would not benefit from digital screening mammography?
Women who fit ALL of the three categories:
For those women, digital and film mammography are equally accurate.
No. At present, only 8 percent of the mammography units in the U.S. are digital systems, whereas approximately 40 percent of women undergoing screening mammography have dense breasts, so it is not possible for all women in the affected categories to receive digital mammograms. Women who would like to have digital mammograms can ask their doctors or contact local hospitals or imaging centers to find out if digital mammography is available in their area.
Women should have their next mammogram when they are scheduled for it. It is better to have a film mammogram when a woman is supposed to have her next mammogram than for her to delay her screening in order to get a digital mammogram. No woman should defer screening with mammography just because of a lack of access to digital mammography. Film mammography has been successfully used as a screening tool for breast cancer for over 35 years.
There is no reason for any woman to receive an extra mammogram because of these trial results. That is, if a woman has had a mammogram in the last year, and she has no breast signs or symptoms, she should undergo her next screening mammogram only when she is due for one, not earlier than she would ordinarily be scheduled.
In DMIST, digital mammograms required approximately three quarters the radiation dose of film mammography. The dose in film mammography is quite low and poses no significant danger to patients.
Multiple exposures to obtain an accurate view of a portion of the breast may be necessary with digital mammography. Is additional radiation dose an issue?
Increasing the number of images per view does not increase the dose dramatically because not all breast tissue is exposed in each view. For example, taking two digital images of the breast instead of one film mammogram does not double the dose overall, since only a portion of the breast is exposed twice. On average, the larger number of digital images required is more than offset by the lower doses delivered by digital mammography for women with thicker and denser breasts.
DMIST did not investigate whether screening mammograms reduce mortality from breast cancer. The trial compared the effectiveness of digital versus film mammography as methods for breast cancer screening.
Many large randomized screening trials have found that film mammography can reduce breast cancer mortality by approximately 18 percent to 30 percent. The inherent assumption in the design of DMIST is that screening mammography reduces breast cancer mortality, and if digital mammography detects the same number or more cancers than film mammography, it is likely to confer an equal or greater mortality reduction through its use in screening.
The American College of Radiology (ACR) and the American Cancer Society (ACS) recommend annual screening mammograms for asymptomatic women 40 years or older, with screening mammography possibly started at an earlier age for women with higher risk. According to the ACR, it is unclear at what age, if any, women cease to benefit from screening mammography. Because this age is likely to vary depending on the individual’s overall health, the decision as to when to stop routine mammography screening should be made on an individual basis by each woman and her physician.
For the general population, the NCI recommends that women in their 40s and older should be screened every one to two years with mammography.