Abstract
Purpose: To determine if MRI features and molecular subtype influence the detectability of breast cancers on MRI in high-risk patients. Methods and Materials: Breast cancers in a high-risk population of 104 patients were diagnosed following MRI describing a BI-RADS 4–5 lesion. MRI characteristics at the time of diagnosis were compared with previous MRI, where a BI-RADS 1–2–3 lesion was described. Results: There were 77 false-negative MRIs. A total of 51 cancers were overlooked and 26 were misinterpreted. There was no association found between MRI characteristics, the receptor type and the frequency of missed cancers. The main factors for misinterpreted lesions were multiple breast lesions, prior biopsy/surgery and long-term stability. Lesions were mostly overlooked because of their small size and high background parenchymal enhancement. Among missed lesions, 50% of those with plateau kinetics on initial MRI changed for washout kinetics, and 65% of initially progressively enhancing lesions then showed plateau or washout kinetics. There were more basal-like tumours in BRCA1 carriers (50%) than in non-carriers (13%), p = 0.0001, OR = 6.714, 95% CI = [2.058–21.910]. The proportion of missed cancers was lower in BRCA carriers (59%) versus non-carriers (79%), p < 0.05, OR = 2.621, 95% CI = [1.02–6.74]. Conclusions: MRI characteristics or molecular subtype do not influence breast cancer detectability. Lesions in a post-surgical breast should be assessed with caution. Long-term stability does not rule out malignancy and multimodality evaluation is of added value. Lowering the biopsy threshold for lesions with an interval change in kinetics for a type 2 or 3 curve should be considered. There was a higher rate of interval cancers in BRCA 1 patients attributed to lesions more aggressive in nature.
Highlights
Multiparametric breast MRI is a highly sensitive modality used as part of the screening protocol for high-risk patients in Ontario’s High-Risk Ontario Breast Screening Program (HR OBSP) [1]
By influencing the detectability of breast cancers on MRI screening in a high-risk population, this study aims to determine which risk factors, features of breast lesions on MRI and type of tumour receptors may be associated with an increased risk of missed cancers on MRI
Patients initially were included via our research algorithm, but upon review turned out not to meet the criteria to be in the OBSP high-risk program: the biopsy results did not come back as malignant or the cancerous lesion was only visible on mammogram as calcifications and not on MRI (Figure 3)
Summary
Multiparametric breast MRI is a highly sensitive modality used as part of the screening protocol for high-risk patients in Ontario’s High-Risk Ontario Breast Screening Program (HR OBSP) [1]. Breast MRI has a high cancer detection rate [2,3], some challenging cases may contribute to missing breast cancers. This has already been described and published with mammograms. Pages in [6] show that the main error in breast MRI interpretation is misinterpretation. The main missed breast cancer finding is a focus [7]. Kinetics pattern contributes to false-negative cases [5,6,7,8,9]
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