The Real Problem With Mammograms: They're Too Good at Finding Things We Don't Understand

This week, the United States Preventive Services Task Force revised their guidelines for breast cancer screening based on a comprehensive review of evidence published in the most recent issue of the Annals of Internal Medicine. Previously, women over 40 were encouraged to schedule a mammogram every year. Now, USPSTF says that women can wait until 50. Though other groups, like Susan G. Komen for the Cure and the American Cancer Society have not changed their recommendations, it's the USPSTF that helps insurers decide what procedures are covered and which aren't.

According to the New York Times,

While many women do not think a screening test can be harmful, medical experts say the risks are real. A test can trigger unnecessary further tests, like biopsies, that can create extreme anxiety. And mammograms can find cancers that grow so slowly that they never would be noticed in a woman's lifetime, resulting in unnecessary treatment.

Overall, the report says, the modest benefit of mammograms—reducing the breast cancer death rate by 15 percent—must be weighed against the harms. And those harms loom larger for women in their 40s, who are 60 percent more likely to experience them than women 50 and older but are less likely to have breast cancer, skewing the risk-benefit equation. The task force concluded that one cancer death is prevented for every 1,904 women age 40 to 49 who are screened for 10 years, compared with one death for every 1,339 women age 50 to 74, and one death for every 377 women age 60 to 69.

Many cancer groups opposed the decision, and it's easy to see why: their job is to ensure that no one, no matter how slim the odds, dies of cancer that could have been prevented. Proponents of evidence-based medicine say that mammograms lead to too many unnecessary tests and the detection of too many tumors that may not really need treatment. But as it turns out, mammograms themselves aren't the problem.

Mammograms, says Dr. Heidi Nelson, are very good at detecting abnormalities in breast tissue. The problem is that we're not yet good at understanding what those abnormalities mean. Dr. Nelson, a research professor in the Departments of Medical Informatics and Clinical Epidemiology and Medicine at Oregon Health Sciences University, lead the comprehensive review upon which the USPSTF's data was based, though she is not affiliated with the group and made no recommendations for how the data should be interpreted. The evidence she's collected has shown a clear trend.

We've come to a point where the ability to detect precancerous cells has outpaced our ability to understand how these cells operate. In many cases women are treated for breast cancer based on precancerous lumps that are only rarely deadly. A better test for certain genetic markers might help researchers understand which precancerous lumps are most likely to turn into a fast-moving cancer, says Nelson, but no test like that exists. For now, doctors treat lots of tumors that may not kill anyone, and women are subjected to a battery of tests that don't provide many answers. "We can't advise people at this stage," says Nelson. "We can only find things."

And we're finding more than ever. "Each year we're picking up more and more lesions that aren't quite cancers," says Dr. Christine Pelligrino, head of the breast health clinic at the Montefiore-Einstein Center for Cancer Care. "We've ID'd lesions over the last 5-10 years that we know are associated with an increase relative risk of developing an invasive breast cancer. For the majority of women, they're not going to actualize that risk," she says. But some will, and it's difficult to tell in whom. "What do you do about it in those women?" Pelligrino asks. In some cases, you watch and wait. In some cases, you treat it, either with chemotherapy or cancer-preventing medications. In all cases, women have to go through a battery of tests, and have to live with the knowledge that there may be a time bomb living inside their bodies—even if the odds are slim.

The debate over whether the benefits of mammograms for women in their 40s outweigh the risk is nothing new. In 1997, Sharon Begley wrote in NEWSWEEK about the mammogram debate, just after the National Institute for Health recommended that women in their 40s not receive annual mammograms (a position they since revised). She noted then, as now, we have minimal answers about the types of tumors we find in younger women.

Confined to the ducts of the breast, [ductal carcinoma in situ, or DCIS] accounts for about 10 percent in all women, and from 15 to 60 percent in women in their 40s.…"It may stay there a woman's whole life and never invade surrounding tissue,'' says Dr. Michael Cohen of Sloan-Kettering, "but we don't know how to tell the one that won't spread from one that will."

Twelve years and a few flip-flopping recommendations later, the research is still unclear. "We find so many [DCIS tumors] on mammography, and we don't know what proportion would ever cause trouble in progressing on to cancer. We don't have good historic information on that," says Nelson. "We treat them like cancer, but a lot would not progress to that point."

Mammograms have long been a source of small comfort for women who fear breast cancer. They're proactive. They're responsible. They feel like positive steps to safeguard one's health. But the truth is, there's only so much a woman can do to protect herself against breast cancer. Perhaps it's time to put the onus not on women to detect breast cancer, but on science and medicine to figure out why some cancerous lesions kill women, and some don't. Until then, we're left with the new guidelines, a lot of controversy, and not much else to help us keep our breasts healthy.

"It's dissatisfying that today we don't have a list of five other things we can do," says Nelson. "We need a lot of research on other fronts, and we just don't have that yet."

The Real Problem With Mammograms: They're Too Good at Finding Things We Don't Understand | News