ARRS 2019: Short-Interval Follow-up MRI in Identifying Early-Stage Breast Cancer
When appropriate, short-interval follow-up magnetic resonance imaging (MRI) can be used to identify early-stage breast cancer and avoid unnecessary biopsies, according to a study presented by Lamb et al at the American Roentgen Ray Society (ARRS) 2019 Annual Meeting (Abstract 2367).
Utilization of MRI for breast cancer screening continues to increase, as it is the most sensitive modality to detect breast cancer. Much more is known about short-term follow-up of probably benign findings (< 2% of malignancy) for mammography than MRI.
Methods
The study was conducted to evaluate the frequency and cancer yield of American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS) 3 lesions in patients undergoing baseline vs nonbaseline high-risk screening MRI exams. Nonbaseline MRI screening exams were defined as those preceded by at least one screening exam.
Consecutive MRI screening exams performed at a large tertiary academic institution from 2011 through 2015 were identified. Outcomes of all BI-RADS 3 assessments were determined through linkage of an MRI mammography information system and a regional tumor registry. All biopsy and surgical pathology results obtained within 2 years of the MRI examination were reviewed. Cases without malignant pathology after 2 years were considered benign. Z-tests were used to calculate differences in the frequency and cancer yield of BI-RADS 3 assessments between patients on baseline vs nonbaseline exams.
Findings
Among the 6,672 MRI screening exams performed in 3,214 patients included in the study, 202 (3.0%) were assigned a BI-RADS 3. Among baseline exams, 8.3% (82 of 983) were assigned BI-RADS 3, compared to 2.1% (120 of 5,689) of nonbaseline exams (P < .01). Thirteen of 202 (6.4%) of the total BI-RADS 3 lesions yielded malignancy, with 12 of the 13 cancers described as either stage 0 or I at diagnosis. The cancer yield of BI-RADS 3 was 2 of 82 on baseline exams (2.4%) vs 11 of 120 (9.2%) on nonbaseline exams (P = .056). Of the 13 diagnosed cancers, 8 were initially characterized as foci, 3 as nonmass enhancement, and 2 as masses. Ten of 13 cancers were upgraded at the 6-month follow-up MRI or before.
The results indicate BI-RADS 3 assessments are significantly more common in baseline vs nonbaseline screening breast MRI exams, and BI-RADS 3 lesions on baseline exams have a lower cancer yield. Most cancers diagnosed on follow-up of BI-RADS 3 lesions are early-stage disease, and most are diagnosed at or before the 6-month follow-up. The results indicate that when employed sensibly, short-interval follow-up MRI is an appropriate technique to identify early-stage breast cancer.
“This study clarifies that probably benign assessments can be as useful for MRI as they are for mammography,” said study coauthor Leslie Lamb, MD, MSc, of Massachusetts General Hospital (MGH) and Harvard Medical School.
“Many patients and providers question the utility of BI-RADS 3 in MRI, particularly as some insurers do not cover the costs of the short-interval follow-up MRIs. This study clarifies that short-interval follow-up MRI is a valuable method of identifying early-stage breast cancer, while avoiding unnecessary biopsies,” noted study coauthor Christine Edmonds, MD, of the Department of Radiology at MGH.
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