False-positive MRI result has little impact on prophylactic mastectomy choice

April 9, 2008

NEW YORK (Reuters Health) - New research indicates that breast MRIs performed in BRCA mutation carriers yield a high rate of false-positive results, yet this appears to have little impact on a woman's choice to undergo or not undergo prophylactic mastectomy.

"The final decision to actually undergo prophylactic mastectomy appeared to be determined more frequently by a woman's prior preference than a positive scan," lead author Dr. Nicoline Hoogerbrugge, from Nijmegen Medical Centre in the Netherlands, said in a statement.

As reported in the Annals of Oncology for April, Dr. Hoogerbrugge and colleagues assessed prophylactic mastectomy rates in 196 BRCA mutation carriers who were followed for a median of 2 years with annual mammography and MRI. The patients' preference for prophylactic mastectomy was recorded at first surveillance after their BRCA status was revealed.

Forty-one percent of women had at least one positive MRI or mammography reading, the report indicates. Cancer was identified in 17 patients: 11 at surveillance, 4 at intended prophylactic mastectomy, and 2 had interval malignancies.

In combination, mammography and MRI were 71% sensitive and 90% specific in detecting breast cancer. MRI had a false-positive rate of 83%.

Among women with a prior preference for mastectomy, the prophylactic mastectomy rates in women with and without false-positive imaging results were 89% and 66%, respectively (p = 0.06). The corresponding rates among women who preferred surveillance were 15% and 11%.

"It is important to give BRCA mutation carriers correct risk information for the decision process, because preventive surgery is irreversible," Dr. Hoogerbrugge emphasized. "This study has made me realize that for women at high hereditary risk of breast cancer, accurate detection techniques are of the utmost importance, even at the cost of a high false positive rate because most women can cope with a false positive MRI result."