Abstract P3-02-02: Predictive value of breast MRI in detecting mammographically occult contralateral breast cancer: Can we target women more likely to have contralateral breast cancer based on primary tumor clinicopathologic factors?
Authors: Susnik B , Lillemoe TJ , Swenson KK , Tsai ML , Finkelstein MJ , Schneider L , Braatz CM , Krueger JL , Rueth N 
Published: May 2019

Abstract
Background: Use of preoperative magnetic resonance imaging (MRI) staging in newly diagnosed breast cancer increases detection of synchronous contralateral breast cancer (CBC) over other screening modalities; however, it is associated with a high false positive rate, additional biopsies, extensive surgical procedures, and possibly increased psychological morbidity.
Specific Aims: To determine predictors of synchronous, mammographically-occult but MRI-detected CBC in women newly diagnosed with breast cancer.
Methods: We performed a retrospective review of patients at Allina Health, Abbott Northwestern Hospital who had preoperative breast MRI prior to surgical resection of their breast cancer from 2010–2014. We collected patient demographic and clinicopathologic data. To determine the association between MRI-detected CBC versus benign findings based on clinicopathologic data, we performed univariate analysis (p&lt;0.05). Multivariate Logistic Regression was used to adjust for covariates and factors predictive of CBC. Area under the Receiver Operating Characteristic Curve provided a measure of model accuracy.
Findings: 1894 patients had pre-operative MRI during the study period. Of those, 201 had suspicious findings on contralateral breast MRI requiring biopsy (table 1). Overall 3% (60/1894) had synchronous CBC (invasive carcinoma or DCIS) detected on MRI. The majority of CBCs (n=60) were stage 0 or IA (85%), ER/PgR+ (98%), HER2- (89%), and low/intermediate grade (80%). Women more likely to have mammographically-occult CBC were older (p&lt;0.001), had lobular versus ductal index cancer (p=0.03), and had ER positive (p=0.027) or PgR positive (p=0.002) tumors. On multivariate logistic regression analysis (ROC area=0.75), PgR positive status (p=0.022), and older age (p=0.004) were predictive of CBC. With each year of additional age, odds of CBC increased by 5%. No CBC was identified in women &lt; age 45 with high risk index cancers (ER- or HER2 +). CBC was 11 times more likely when PgR status was positive versus negative. CBCs were diagnosed significantly more frequently in patients with index cancers that were hormone receptor positive and HER2 negative compared to HER2 positive or triple negative invasive index cancers (Fisher's exact test; p=0.041).
Risk of CBC by Index Cancer TypeIndex CancerCBC n (%)DCIS (n=51)15 (29)Invasive carcinoma (n=150)45 (30)ER+/HER2- (n=121)41 (34)HER2 positive (n=18)3 (17)Triple Negative (n=11)1 (9)Total (n=201)60 (30)
Conclusions: Preoperative MRI is effective in detecting mammographically-occult early stage, hormone receptor positive CBC in older women. MRI-detected CBC is more common in patients originally presenting with hormone receptor positive and HER2 negative index cancers. Our results suggest that it may be possible to determine a subset of patients who are less likely to benefit from a preoperative breast MRI, an important implication in an era of increasing healthcare cost utilization awareness.
Citation Format: Susnik B, Lillemoe TJ, Swenson KK, Tsai ML, Finkelstein MJ, Schneider L, Braatz CM, Krueger JL, Rueth N. Predictive value of breast MRI in detecting mammographically occult contralateral breast cancer: Can we target women more likely to have contralateral breast cancer based on primary tumor clinicopathologic factors? [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-02-02.