Time to Enhancement of Foci Relative to Background Parenchymal Enhancement on Ultrafast Breast MRI: A Single-Center Retrospective Study

BACKGROUND - Breast MRI is a sensitive tool for detecting small cancers. However, differentiating benign and malignant lesions remains challenging, particularly for foci. Studies evaluating other lesion types have identified ultrafast MRI (UFMRI) parameters associated with malignancy. OBJECTIVE - The purpose of this study was to determine if kinetic features of UFMRI can differentiate malignant and nonmalignant foci. METHODS - In this single-center retrospective study, consecutive UFMRI examinations performed from July 2019 to April 2023 with subsequent MRI-guided biopsy of a focus were selected. Patient characteristics and lesion features were collected from the EMR, imaging reports, and imaging review. Focus and background parenchymal enhancement (BPE) time to enhancement (TTE), and the difference between them was calculated. Associations with malignancy were assessed with univariable and multivariable logistic regression. RESULTS - A total of 124 patients (mean age, 53 years old; range, 29-78 years old) underwent biopsy of 124 foci. Sixty-four (51.6%) were postmenopausal, 71 (57.3%) had a personal history of breast cancer, 81 (65.3%) had a family history of breast cancer, and 33/94 (35.3%) had genetic mutations. Most examinations were performed for extent of disease evaluation (47.6%; 59/124), followed by screening (41.9%; 52/124). Patients predominantly had heterogeneous fibroglandular tissue (58.1%; 72/124) and mild BPE (57.3%; 71/124). Of 124 lesions, 21 (16.9%) were malignant, 16 were invasive, and five were ductal carcinoma in situ. Odds of malignancy increased 5% with each 1-second increase in the difference of lesion TTE and BPE TTE (95% CI: 2-9%, p = .006). Older age and lower BPE were associated with increased likelihood of malignancy (p = .005 and p = .02, respectively). Odds of malignancy for patients with minimal or mild BPE were 11.69 times the odds of those with moderate or marked BPE (95% CI: 1.51-90.67). No other demographic or lesion characteristics were predictive of malignancy. CONCLUSION - Earlier visualization of a focus relative to BPE on UFMRI was associated with increased likelihood of malignancy; morphologic features showed no association with malignancy. CLINICAL IMPACT - The difference of TTE of a focus compared with that of BPE may be a useful parameter for assessing malignancy, which could help reduce unnecessary biopsies.