Can follow-up controls improve the confidence of MR of the breast?: A retrospective analysis of follow-up MR images of the breast.

Purpose: To assess the change in diagnostic confidence between first and follow-up dynamic MR examination of the breast (MRM). Methods: The reports of a total of 175 MRM in 77 patients (mean age 50 years: 36-76) with 98 follow-up MRM were analyzed. All examinations were performed as a dynamic study (Gd-DTPA, 0.16 mmol/kg; 6-7 repetitive studies). The change in diagnostic confidence was retrospectively classified as follows: controlled lesion vanished during follow-up (category I); diagnostic confidence increases during follow-up (II), more likely benign (IIa), more suspicious (IIb): no difference in diagnostic confidence (III). Long-term follow-up over an average of four years was obtained for 57 patients with category IIa/III findings. Results: In 98 follow-up examinations, only two lesions vanished (2%). In 77/98 erases a category IIa lesion was diagnosed, in 11 cases a category IIb lesion. In 8 cases (8%) there was no change in diagnostic confidence during follow-up. Lesions in category IIb underwent biopsy in 10/11 cases, in one case long-term follow-up proved a completely regredient inflammatory change. In 8/11 suspicious findings (IIb) a malignant tumor was detected. The mean time interval between first and follow-up MRM was 8 months for I-IIb lesions, and 4 months for category III lesions. In the longterm follow-up two patients with a category IIa lesion developed a carcinoma in a different breast area after four and five years. Conclusion: MRM follow up increases the diagnostic confidence if the time interval is adequate (>4 months). A persistently or increasingly suspicious finding warrants biopsy.