Breast cancer rates in Canada fell by six per cent in 2003 following a report linking hormone replacement therapy (HRT) to increased risks of breast cancer. That report prompted many women to stop taking HRT, and this might explain part of the drop in breast cancer rates. But screening mammography is also responsible for much of the decrease in fatal cases. “Mammograms save lives,” says Dr. Verna Mai, the director of screening for Cancer Care Ontario.

Here’s what you need to know about mammography.
 
1. Recommendations for age at first mammogram vary.
The Canadian Cancer Society recommends that women have a mammogram every two years beginning at age 50. The American Cancer Society, along with other organizations in the United States, recommends that women have their first mammogram at age 40 followed by yearly screening. Canadian women likely wouldn’t be refused a mammogram at age 40, though – at least not in Ontario or British Columbia. Dr. Supriya Kulkarni, an assistant professor of medical imaging at the University of Toronto, and Dr. Christine Wilson, a clinical associate professor of diagnostic imaging at the University of British Columbia in Vancouver, both feel that after the first mammogram a woman should be screened yearly.

An analysis of five scientific studies by the National Cancer Institute in the United States showed that mammography reduced breast cancer deaths by 30 per cent in women aged 40 to 49, and by more than that in older women.

The bottom line: “A woman should have a mammogram as often as her physician wants her to have one,” says Kulkarni.

2. Standard and digital mammography are generally equally effective at detecting cancer, but digital exams take less time.
Digital images come up almost immediately, whereas images with standard X-ray film take longer to process, says Wilson.

A shorter exam time might benefit women who find mammograms painful, including some women with small or tender breasts, says Kulkarni. If your breasts are tender and you’re still menstruating, try scheduling your mammograms just after your period, when breasts are least tender.

Digital mammography requires less radiation than standard mammography, too. However, the amount of radiation required to capture breast images is only “a small fraction” of the radiation we get from being outside on a daily basis, says Wilson.

Of note: Digital mammography is better than film mammography at detecting breast cancer among women under the age of 50 and in those with dense breasts. (Density is determined by the amount of supporting tissue in the breast compared with fat; cells in dense breast tissue can become cancerous while fat cells can’t.)

3. Women with dense breasts need more frequent surveillance.
The more dense the breast is, the more difficult it is for a mammogram to detect cancer cells. A study carried out at the Princess Margaret Hospital in Toronto under Dr. Norman Boyd found that women with dense breasts are five times more likely to develop breast cancer than those whose breasts have a lot of fatty tissue. A woman can’t determine density on her own. HRT can increase breast density while age decreases it, and breast size has no effect.

4. Magnetic resonance imaging (MRI) is sometimes used in addition to mammography.
Some experts recommend MRI along with mammography for women at high risk for breast cancer and for those who have already had cancer in one breast. However, “Mammography is the only gold standard we know for breast cancer screening,” says Kulkarni.

Check out our Breast self-exam guide.

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Originally titled "Mammography," from the October 2007 issue of Canadian Living Magazine, on newsstands or click here to purchase online.