To Test Or Not To Test?

By Christine Gorman

Breast cancer researchers have been arguing for two years about an issue that most women, in the U.S. at least, thought was settled: whether routine mammograms save lives. Given that tens of millions of these tests are performed each year, the women who get them deserve some clarity on the issue. Instead they're getting an old-fashioned academic feud with lots of heat and very little light.

The debate flared up again last week when an independent advisory panel to the National Cancer Institute concluded that a harsh critique by two Danish researchers of the data supporting mammography's benefits had enough merit that its conclusions should be addressed in the cancer database maintained by the NCI. For now, the cancer institute is not changing its basic recommendation that women age 40 and older undergo routine mammograms. But it is planning to review the policy. "This is a very complex issue," says Dr. Peter Greenwald, director of cancer prevention at the NCI. "It doesn't mean that it's wrong [to get a mammogram], just that it's less certain than we thought."

In trying to sort out what women should make of this controversy--and whether they need to keep their next mammogram appointment--it helps to have a little background. The most important thing to keep in mind is that the debate is about mammograms used to screen healthy women. Researchers are not talking about mammograms that are ordered after a lump has been discovered. Nor are they talking about women previously treated for breast cancer or those who are at high risk because of, for example, a strong family history of the disease.

The authors of the Danish study, which was published in the journal Lancet last October, focused on routine mammography of healthy women. They reviewed seven large clinical trials--several of them 30 years old--that were designed to figure out whether such mammograms actually saved lives. Using the most up-to-date standards of what makes a good clinical trial, they concluded that five of the studies were so primitive or of such poor quality that their conclusions could not be trusted. Those five included ones that found that routine mammograms reduce a woman's risk of dying from breast cancer by 30%. The two remaining studies found no benefit. The authors' conclusion: there is no reliable evidence that women who get mammograms live any longer than women who don't.

The reaction in the medical community was immediate--and fierce. Critics argued that the methodology of the Danish review was flawed and that several studies were too hastily thrown out. Others pointed out that both mammography and breast cancer treatments are better now than they were in the 1970s and '80s, when some of those studies were conducted. Some breast cancer advocates have even wondered whether the Danish researchers might have had an economic or a political incentive to downplay the benefits of what are fairly expensive screening programs.

When you cut through all the arguments and counterarguments, what you realize is that everyone expects too much of mammograms. Even the best miss 10% to 15% of breast cancers. Mammograms are also associated with a high rate of false positives--particularly among younger women. In the U.S. only 2% to 11% of all "abnormalities" found in a routine screening actually turn out to be cancer. That translates into a lot of anxious women who are called back for another mammogram or advised to undergo either a needle aspiration or a biopsy. These can lead to problems such as scarring, infections and the complications of unnecessary surgery.

Despite these drawbacks, there are very real benefits to mammograms. The earlier a cancer is found, the more options a woman usually has with regard to treatment--something the Danish review did not address. Many women with smaller tumors, for example, may be able to forgo chemotherapy, opting for breast-sparing surgery and hormonal treatment. To these women, a few anxiety-provoking false positives may seem like a small price to pay.

True, some slow-growing tumors will be treated when they probably don't need to be. And maybe someday doctors will know how to identify those cases and say with confidence, "We don't need to touch this cancer because it won't kill you until you're 85." But we're not there yet.

As with so many things in medicine, doctors and patients are left making decisions based on incomplete information. "We have to be honest about saying that [routine] mammography may not save your life," says Dr. Patricia Ganz, a professor at the schools of medicine and public health at UCLA. But it can give a woman who discovers she has breast cancer options she might not otherwise have. And who wouldn't want that?