The impact of a false positive MRI on the choice for mastectomy in BRCA mutation carriers is limited

N. Hoogerbrugge1, Y.J.L. Kamm, P. Bult, K.M. Landsbergen, E.M.H.F. Bongers, H.G. Brunner, H.J. Bonenkamp, J.A. de Hullu, M.J.L. Ligtenberg, C. Boetes
Department of Human Genetics, Radboud University Nijmegen Medical Centre1

Purpose: To assess the false positive rate of breast cancer surveillance by MRI in BRCA mutation carriers and the impact of an abnormal mammography or breast MRI on the patients decision for prophylactic mastectomy.

Patients and methods: 196 BRCA mutation carriers were included with a median follow-up of 2 years [range 1-9] with annual mammography and MRI. Preference for prophylactic mastectomy was registered at first surveillance after the mutation carriership was revealed.

Results: 41% (81/196) of the women had at least one positive MRI or mammography. Malignancy was detected in 17 women: eleven at surveillance, four at an intended prophylactic mastectomy and two had an interval cancer. Imaging by mammography and MRI had a sensitivity of 71% and a specificity of 90%. The probability that a positive MRI result is false positive was 83%. In the group with a prior preference for mastectomy with and without a false positive imaging prophylactic mastectomy was performed in 89% and 66%, respectively (p=0.06), in the group with prior preference for surveillance these percentages were 15% and 11% respectively (p=0.47).

Conclusion: Although the rate of false positive MRI results is high, the impact on the choice for prophylactic mastectomy is limited, and is determined by the womans' preference prior to the establishment of a BRCA mutation.