An examination of risk
With pink ribbons, pink gift cards and pink Playtex gloves, who could miss Breast Cancer Awareness month? But pink isn’t the only thing present in abundance this month. Statistics are too: 1 woman in 8 will get breast cancer; more women are diagnosed with breast cancer now than 25 years ago; and early detection saves lives. There is more to those numbers than meets the eye -- and some debate among scientists about what the numbers mean.
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October’s saturation of breast cancer information probably has many women wondering if anything else is nearly as dangerous to their health. But while all agree that breast cancer is a serious concern for women, some health professionals think the risk has been blown out of proportion, sometimes to the detriment of more pressing issues, such as lung cancer (which will kill almost twice as many women in 2006).
“Women have definitely been overly frightened,” says Dr. Diana Petitti, senior advisor in health policy and medicine at Kaiser Permanente in Pasadena. “I particularly think for the younger women, there is a misperception of how high a risk of death [breast cancer poses] and how common it is.”
For one thing, “the lifetime number is misleading,” says Dr. Steven Woloshin, an internist at Dartmouth Medical School in Hanover, N.H. “What you really want to know is, ‘What’s the chance I’m going to get breast cancer in the foreseeable future?’ ” While “1 in 8” means about a 12% lifetime chance of getting the disease, the chance of a 40-year-old woman getting breast cancer and dying of it by age 50 is one-third of 1%. (The chance of dying from any cause by her 50th birthday is about 2%).
Breast cancer rates have been rising for 25 years although they appear to be leveling off, says Dr. Michael Thun, head of epidemiological research for the American Cancer Society in Atlanta.
But does that mean more women in this century have been doing something, or exposed to something, that gives them breast cancer? Probably not, Thun says, because early detection from screening methods such as mammograms has resulted in more breast cancer being found. What health professionals don’t know is how many of those cancers would never have become life threatening. “Is it a real increase in cancer or a function of screening that finds nonthreatening cancer? That’s really hard to know,” Woloshin says.
He describes the problem this way: For every 2,000 women getting mammograms, one woman will be diagnosed with a life-threatening breast cancer -- and, through early detection and treatment, will have her life prolonged. Ten will have more benign forms of breast cancer that probably wouldn’t have threatened their lives even if they hadn’t been treated, but will get treated for them nonetheless. An additional 200 will have biopsies, and find that the mammogram’s positive result was a false alarm: no cancer of any kind.
The problem is that medical science can’t tell which cancers detected by mammography and biopsy will turn out to be life threatening, so they have to treat them all.
There has been controversy among scientists about the age at which women should get mammograms because the chances of their actually getting the disease in their 40s, for example, is low, and they run a high risk of having unnecessary biopsies and treatments, Petitti says.
Some good news among all the statistics: “Real survival is improving,” Thun says. The death rate from breast cancer has been dropping steadily since 1990 and is still going down. The reason for the continuing decline, he says, is evenly divided between earlier diagnosis -- which for nastier cases improves the odds of surviving -- and better treatment.
Yet, not everyone is convinced even of this. Petitti and Woloshin say the improved mortality rate might partly be due to the fact that more nonharmful cancers are being found these days, stacking the deck in favor of survival.
Organizations such as the National Breast Cancer Foundation and the American Cancer Society recommend yearly mammograms starting at age 40. The data for 40-year-olds show there is a benefit for screening, Petitti says, but it is small. The test only provides a small but clear benefit in extending life when women reach their 50s and 60s, she says. For these reasons, she and Woloshin argue that screening is a personal decision that women should make based on their own circumstances -- such as family history, age and comfort level with risk.
The National Institutes of Health website has a “risk calculator” called the Breast Cancer Risk Assessment Tool to help women evaluate their status. Women enter information such as their age, the number of family members who’ve had the cancer, the age at which they had their first full-term pregnancy, and the calculator computes the chance that they will be diagnosed with breast cancer within the next five years. Such tools, Woloshin says, “allow a woman to make a rational choice about screening that is consistent with her values.”
The Breast Cancer Risk Assessment Tool can be found at www.cancer.gov/bcrisktool/.
Despite the debates and statistical nuances, overall, “screening does lower your chance of dying from breast cancer,” Woloshin says. And a 2000 study he conducted showed that most women are willing to deal with the consequences of a false positive given the chance that some lives will be saved, including perhaps their own.
-- Mary Beckman
