Background: Magnetic resonance imaging (MRI) can detect breast cancer in high-risk patients, but is associated with a significant false-positive rate resulting in unnecessary breast biopsies. More data are needed to define the role of MRI screening for specific high-risk groups. We describe our experience with MRI screening in patients with atypical hyperplasia (AH) and lobular carcinoma in situ (LCIS).
Methods: We retrospectively reviewed data from our high-risk screening program prospective database for the period from April 1999 (when screening MRI was first performed at our institution) to July 2005. Patients with AH or LCIS demonstrated on previous surgical biopsy were identified. All patients underwent yearly mammography and twice yearly clinical breast examination. Additional screening MRI was performed at the discretion of the physician and patient.
Results: We identified 378 patients; 126 had AH and 252 had LCIS. Of these, 182 (48%) underwent one or more screening MRIs (mean, 2.6 MRIs; range, 1-8) during this period, whereas 196 (52%) did not. Those who had MRIs were younger (P < 0.001) with stronger family histories of breast cancer (P = 0.02). In MRI-screened patients, 55 biopsies were recommended in 46/182 (25%) patients, with 46/55 (84%) biopsies based on MRI findings alone. Cancer was detected in 6/46 (13%) MRI-generated biopsies. None of the six cancers detected on MRI were seen on recent mammogram. All six cancers were detected in five patients (one with bilateral breast cancer) with LCIS; none were detected by MRI in the AH group. Thus, cancer was detected in 5/135 (4%) of patients with LCIS undergoing MRI. The yield of MRI screening overall was cancer detection in 6/46 (13%) biopsies, 5/182 (3%) MRI-screened patients and 5/478 (1%) total MRIs done. In two additional MRI-screened patients, cancer was detected by a palpable mass in one, and on prophylactic surgery in the other and missed by all recent imaging studies. For 196 non-MRI-screened patients, 21 (11%) underwent 22 biopsies during the same period. Eight of 22 (36%) biopsies yielded cancer in seven patients. All MRI-detected cancers were stage 0-I, whereas all non-MRI cancers were stage I-II.
Conclusion: Patients with AH and LCIS selected to undergo MRI screening were younger with stronger family histories of breast cancer. MRI screening generated more biopsies for a large proportion of patients, and facilitated detection of cancer in only a small highly selected group of patients with LCIS.