Every year for the past decade, about one third of women with breast cancer have had a breast removed. They've done this despite medical guidelines advocating less drastic breast-conserving surgery and even though survival rates for the two different operations are equal–80 to 90 percent or even higher.

Have they been bullied into this by aggressive surgeons with out-of-date ideas? No, says cancer care researcher Steven Katz, coauthor of a new study on treatment choices.

"Much of the time it's women's own idea, and often the choice is quite rational," he says.

The notion that it is doctors who are pushing mastectomies has become so enshrined that many states have passed laws that require surgeons to inform patients about breast-conserving options like lumpectomies. But the mastectomy rate hasn't dropped, says internist Ann Nattinger of the Medical College of Wisconsin. "And that's led a lot of us to feel there was a strong patient component in these decisions. Now Steven has shown it."

Katz and his colleagues, as reported in the August 20 issue of the Journal of Clinical Oncology, surveyed 1,844 women who had recently been diagnosed with breast cancer. The women were asked about their treatment choices and about their doctors' guidance.

"More than a third of these women said their surgeons actually recommended lumpectomy over mastectomy. Another third said the doctor made no recommendation and just laid out the options," says Katz, an internist at the University of Michigan Medical School. "Only about one fifth felt their surgeons recommended a mastectomy, and usually that was because the cancer had spread to several places within the breast, so mastectomy was indicated."

Most striking was that 80 percent of the women reported they felt very involved in making their treatment decisions and not pushed around. And the more involved a woman felt, the more likely she was to choose a mastectomy.

There are a few reasons for this, Katz says. One is that while mastectomy and lumpectomy have equal survival rates, there's a greater chance that cancer will recur after a lumpectomy. (The rates are about 1 percent versus 10 percent.) Even though the recurring cancer is successfully treated—remember those equal survival rates—the thought that the illness might come back scares some women away from lumpectomy. "You can't blame people for that. You don't know what it's like until you have the disease," Katz says.

Another reason is that recurring cancer means recurring treatment, and cancer treatment is not pleasant. "There's more surgery, chemotherapy, and more radiation," says Katz. "None of that makes you feel good." And mastectomy is one way to avoid all that, even if the surgery and changes in body image are more severe.

What all this means to patients "is they should recognize their values are important," says Nattinger. "Often breast cancer patients feel they need to decide on a treatment immediately, but in reality they have a few weeks. Research has shown that a couple of weeks doesn't change the outcome, except in very serious cases. So women should take that time to explore their values, to understand what's most important to them, and make decisions based on that insight."