BUFFALO, N.Y. -- According to a new study, one in three women with breast cancer detected by a mammogram are treated unnecessarily.

The Danish study, "Annals of Internal Medicine," raises the possibility that some women who believe their lives were saved by mammograms could have been harmed by them.

However, when 2 On Your Side took this to Doctor Ermelinda Bonaccio, Chief of Breast Imaging at Roswell Cancer Institute, she says she believes far fewer women are over-diagnosed than this study found.

"I don't believe it's going to change guidelines. I think women should...be aware of it -- but they should not have this affect their decision to have a screening mammogram."

Dr. Bonnaccio says she continues to recommend annual mammograms for women starting at age 40.