If Breast Cancer Can Vanish on Its Own, Do You Still Need Mammograms?

1 in 5 breast cancers detected by screening would disappear without treatment, study suggests.

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Woman getting mammogram

The mammogram has suffered a lot of setbacks in recent years. Breast cancer researchers have questioned the value of the screening test in women younger than 50 and berated the X-ray for its high rate of false positives, those suspicious-looking abnormalities that turn out to be benign. Now, the test itself takes another hit, though women may actually benefit from the news in the end. Some tumors that mammography accurately diagnoses, it seems, may not need treatment. According to a study published in yesterday's Archives of Internal Medicine, a fraction of the tumors it detects would vanish on their own.

The researchers compared about 2,000 Norwegian women ages 50 to 64 who either had screening mammography three times in four years or just one mammogram at the end of the four-year study. The frequently screened group had 22 percent more breast cancers diagnosed compared with the one-time-only group, which could mean that some of the tumors detected initially in the first group would have regressed had they not been spotted. "The hypothesis suggests that about 20 percent of the women in the multiple screen group received unnecessary treatment because the tumors would have disappeared on their own," write the authors of an editorial that accompanied the article.

If doctors can eventually figure out which cancers will disappear on their own—something the new study doesn't do—the discovery could be a great boon for patients. But for now, it's very troubling when one considers how many women may needlessly go through the awful downsides of treatment, including balding, nausea, and early menopause—to say nothing of the disfiguring surgery that can destroy a woman's body image.

On the other hand, mammograms have been shown to lower your risk of dying from breast cancer by 20 to 35 percent (depending on which study you look at) if you're over 50 and by up to 20 percent if you're between 40 and 50.

So, what are you supposed to do?

"At the moment, nothing different," says Susan Love, a clinical professor of surgery at the University of California-Los Angeles medical school and president of the Dr. Susan Love Research Foundation, which focuses on breast cancer. "I think this study does show that some cancers do regress, but that doesn't say to us that mammograms are no good."

What it does indicate is that breast cancer may be like prostate cancer—many men develop prostate cancers that would never wind up killing them. Perhaps some breast cancers found on mammograms can be simply monitored every year with mammograms, ultrasound, or MRI to see if they progress—a type of "watchful waiting" approach now taken with many older prostate cancer patients. "But we're not there yet," Love says. "We need to do studies first to see which cancers we don't need to worry about."

Scientists are already starting to use genetic tests like MammaPrint to determine the superbad breast cancers—the ones most likely to spread everywhere—that call for total destruction with chemotherapy. They've also identified a type of breast tumor called the "almost normal" kind that usually stays put and behaves itself. "I wouldn't be surprised if this particular type was the one that disappeared on its own," says Love. But, at the moment, this is just a hunch. Until researchers know more about these apparently harmless cancers, women over 40 should keep on getting those regular mammograms and the full course of treatment for any breast cancer.

Here's more on determining whether your breast cancer requires chemo and ways to make your mammograms more accurate.