Mayo Clinic researchers evaluated mastectomy trends by year and by use in 5,414 women who had surgery for early-stage breast cancer at the Mayo Clinic from 1997 to 2006.

The mastectomy rate declined from 44 percent in 1997 to 30 percent in 2003, but rose to 43 percent in 2006. During this time, the percentage of women who had breast MRI more than doubled, from 11 percent in 2003 to 23 percent in 2006.

Lead author Dr. Rajini Katipamula says the reasons for this increase are unclear, but women at the Mayo Clinic who underwent diagnostic magnetic resonance imaging prior to surgery to treat early-stage breast cancer had a higher rate of mastectomy, compared to women who did not have an MRI.

"We found that if a woman undergoes an MRI before surgery, she is about 10 percent to 15 percent more likely to have a mastectomy, compared to women who did not undergo MRI," Katipamula said in a statement.

The findings are scheduled to be presented May 31 at the 44th annual meeting of the American Society of Clinical Oncology.