Young women with breast cancer often overestimate both their chance of developing cancer in the other breast  and how much removal of that breast is likely to protect them.

That’s the finding of a new U.S. study of women diagnosed with cancer in one breast between ages 26 and 40 who chose to have a double mastectomy.

Almost all said a desire to extend their life  was a very important part of the decision.

However, the study finds that removing the cancer free breast does not improve survival rates.

Shoshana Rosenberg, is with the Susan F. Smith Center for Women’s Cancers at the Dana-Farber Cancer Institute in Boston.

She says many women with breast cancer are having both breasts removed unnecessarily.

The study recommends that physicians to take the time to talk to their patients about their risk of getting cancer in the opposite breast.