The number of women getting double mastectomies after a breast cancer diagnosis has been rising in the past 10 years, even though most of them don't face a higher risk of getting cancer in the other breast.
That has cancer doctors troubled, because for those women having the other breast removed doesn't reduce their risk of getting breast cancer again or increase their odds of survival. And they don't know why women are making this choice.
Worry about the cancer coming back is one of the biggest reasons, according to a study of women in Michigan and California that tried to figure out which women decided on a double mastectomy, and why.
Women who had a breast MRI were more likely to decide on a double mastectomy, even if the scan didn't show more cancer.
"Usually there's something on the image that can't be fully explained," says Sarah Hawley, an associate professor at the University of Michigan and lead author of the study, which was published Wednesday in JAMA Surgery. "The thing that shows up on the MRI may well be nothing, but it's really difficult to know that you saw something unusual and then not worry about it."
Hawley and her colleagues looked at 1,447 women who were diagnosed with breast cancer in one breast from 2005 to 2007 or from 2009 to 2010. In all, 19 percent of the women seriously considered having a double mastectomy, and almost 8 percent of them decided to have that surgery.
More than two-thirds of the women who had the double mastectomy — 69 percent — had no genetic or family risk factors that would make it more likely that they would get breast cancer again.
Women with more education were more likely to choose double mastectomy, the study found, as were women who had had genetic testing, even if the results came back showing they had no increased risk.
That surprised Hawley; she thought women who got good news on a genetic test would be less likely to then have a prophylactic mastectomy. She doesn't know if simply having a genetic test is enough to get women thinking seriously about double mastectomy, or if they're making the decision before they get the results back.
Hawley studies how patients make decisions about cancer treatment and says this study raises a big question: Are women not understanding the risk information that doctors communicate, or do they understand and decide to go ahead with the surgery anyway?
"I think the answer is both are going on," Hawley says. "Women are hearing the message but not completely understanding. Risk information is difficult to convey and understand, especially when you're getting a cancer diagnosis. And even when women understand, they are choosing to go ahead."
Most women won't lower their risk of cancer by getting a double mastectomy because their risk of getting breast cancer again was already very low. And removing the noncancerous breast doesn't affect the survival rate from the existing cancer.
For women who don't have a family history of breast cancer or the BRCA genetic mutations, other cancer treatments, including lumpectomy and single mastectomy, can improve a woman's chances just as much as double mastectomy, Hawley says.
"Not feeling like double mastectomy is the only thing you can do to 'do everything possible' would be a good thing to get out there," she adds. "it seems like there's pressure to consider it now, and if you don't do it you're not doing everything possible."
Hawley is testing a decision tool aimed to help women weigh their choices for breast cancer treatment and hopes that it will help reduce the anxiety that comes with a cancer diagnosis and the difficult decisions that follow.