High Cost of Breast Cancer Screening
Mammograms save lives, or not. It's one of those perennial controversies: does screening women's breasts with X-rays actually cut the risk of dying from breast CANCER? Some researchers suggest women who have regular mammograms are 15 per cent less likely to die from the disease than women who don't bother. Then again, a Canadian study just last week showed women with particularly dense breast tissue are five times more likely to contract the cancer, and mammograms are less useful for them because the tissue density makes it hard to see the uncontrolled cell growth. Then there are those who wonder whether mammograms detect cancer soon enough, considering that, on average, the disease will have been growing for between six and 10 years by the time a technician is able to spot it on a mammogram. Maybe there's a better way.
Dr. Steven Narod thinks so. By one key measure, Narod is the best breast cancer scientist in the world. The director of the familial breast cancer research unit at the Women's College Research Institute in Toronto, he published 193 studies between 1994 and 2004, which in turn were cited an unsurpassed 11,624 times by other scientists in their own papers, an irreproachable indicator of merit in a body of work. So Narod and his colleagues bring a certain clout to anything they do, including their current effort to assess which is better at finding breast cancer: mammography or magnetic resonance imaging. Narod's team has screened hundreds of women. "We missed one cancer [with the MRI] in six years. The mammography hasn't found one cancer missed by the MRI and, in contrast, the mammography only found one-third of the cancers detected by the MRI," Narod says. "These are not subtle differences."
Unfortunately, neither is the difference in cost. A mammogram is about $80, MRIs about $1,000. So Narod argues provincial governments should refocus on screening smaller numbers of women - those with an identifiably higher risk - but with better technology. "I feel awkward to be in the position of telling my patients, 'I'm recommending you a technique that doesn't really work very well, but it's cheap.' " A $400 MRI is within reach, Narod believes, in part by developing better software to analyze the images. At the same time, the number of so-called false-positives, in which a woman screened by an MRI is told she may have cancer when in fact she does not, needs to come down to reduce needless worry. "That's a solvable problem," says Narod, adding technicians improve with experience. "Our false-positive rate has dropped a ton since we started the study."
Still, mammography enjoys strong support. European studies have suggested a decline in mortality from breast cancer that is directly related to early detection by mammograms, says Dr. Karen Gelmon, who heads the BC Cancer Agency's breast tumour group. "One of the things we have to recognize is that mammograms, although they're not perfect, are very, very good," Gelmon says. "In women above 50 who get regular mammograms done in a reputable place, the false-negative rate [in which the cancer is missed] is only 15 per cent, and in women 40 to 50 who have denser breasts, it's about 25 per cent."
The way it's supposed to work now - and Gelmon says it does in B.C. - is that women at very high risk are supposed to have ready access to an MRI. (These include women with a mutation in either the BRCA1 or BRCA2 gene, or have a family history of the disease.) Unfortunately, that isn't always the case, particularly in Ontario. Dr. Ellen Warner, an oncologist at Sunnybrook Health Sciences Centre in Toronto, sits on a provincial committee studying who should be screened with an MRI. Right now, decisions are made haphazardly. "The same woman might get [an MRI] in one city, and not in another," Warner says. "Even within the same city, she could get one at one hospital, but at another hospital, they will turn her down."
One of the recurring knocks against MRIs is they haven't been proven to reduce mortality. Narod says that's a red herring, noting provincial governments agree that detecting cancers when they're as small as possible is the best possible approach. And from his research, Narod knows MRIs do that much better: "I think it's a rational decision for the government to say, 'No, we don't want to pay that much money to screen and prevent breast cancer because it will cost us too much money, invested as a society, to prevent one case of breast cancer.' For political reasons, they don't say that. They say, 'Well, it hasn't been proven to work.' " Narod's opinion? "It'll work. How confident am I? Ninety-nine per cent. Others will say that I'm speculating." And others still will want an MRI.
Maclean's February 5, 2007