E! News host Guiliana Rancic announced Monday that she plans to have a double mastectomy to remove not only her breast in which cancer has been detected but also her apparently healthy other breast.

Rancic’s decision to undergo that prophylactic, or preventative, surgery is reportedly based on her desire to be done with worrying about breast cancer. As she said when announcing her decision on the Today show, “All it came down to was just choosing to live and not looking over my shoulder for the rest of my life.”

That will strike a chord with many women, whether they’ve been diagnosed with breast cancer or not, for whom the threat of breast cancer seems always to be looming.

But new research suggests that women who have CPM, or “contralateral prophylactic mastectomy” -- which removes that second, healthy breast as a preventative measure -- may not benefit as much as they might expect. In fact, according to a study presented Wednesday at the San Antonio Breast Cancer Symposium, the health benefit of such surgery is, for most women, far outweighed by losses in quality of life.

Using statistical models based on findings from existing studies, researchers led by Robert Prosnitz, an assistant professor of radiation oncology at the Perelman School of Medicine at the University of Pennsylvania, determined that women who have CPM see a very modest gain in life expectancy. But even the slightest decline in quality of life a woman might experience after CPM -- resulting from altered body image or ill effects from radiation treatment, for instance -- completely offset that small benefit. Only a woman who suffered absolutely no loss of quality of life would benefit from CPM, the study found.

The equation depends in part on the fact that the risk of death from the original cancer far outweighs the risk of death from a cancer occurring in the other breast. According to the research, that remains true regardless of the woman’s age, the stage of her original cancer or the cancer’s subtype. The research concludes that very few women can enter a discussion about CPM completely confident that they won’t mind having lost the second breast even the tiniest bit and that physicians should take that into consideration when talking with patients about CPM.