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TOMOGRAPHY, December 2016, Volume 2, Issue 4: 378-387
DOI: 10.18383/j.tom.2016.00247

Effect of MR Imaging Contrast Thresholds on Prediction of Neoadjuvant Chemotherapy Response in Breast Cancer Subtypes: A Subgroup Analysis of the ACRIN 6657/I-SPY 1 TRIAL

Wen Li1, Vignesh Arasu1, David C. Newitt1, Ella F. Jones1, Lisa Wilmes1, Jessica Gibbs1, John Kornak2, Bonnie N. Joe1, Laura J. Esserman3, Nola M. Hylton1, and ACRIN 6657 Trial Team and I-SPY Investigators Network

1Departments of Radiology and Biomedical Imaging, 2Epidemiology and Biostatistics, and 3Surgery, University of California San Francisco, San Francisco, California

Abstract

Functional tumor volume (FTV) measurements by dynamic contrast-enhanced magnetic resonance imaging can predict treatment outcomes for women receiving neoadjuvant chemotherapy for breast cancer. Here, we explore whether the contrast thresholds used to define FTV could be adjusted by breast cancer subtype to improve predictive performance. Absolute FTV and percent change in FTV (∆FTV) at sequential time-points during treatment were calculated and investigated as predictors of pathologic complete response at surgery. Early percent enhancement threshold (PEt) and signal enhancement ratio threshold (SERt) were varied. The predictive performance of resulting FTV predictors was evaluated using the area under the receiver operating characteristic curve. A total number of 116 patients were studied both as a full cohort and in the following groups defined by hormone receptor (HR) and HER2 receptor subtype: 45 HR+/HER2-, 39 HER2+, and 30 triple negatives. High AUCs were found at different ranges of PEt and SERt levels in different subtypes. Findings from this study suggest that the predictive performance to treatment response by MRI varies by contrast thresholds, and that pathologic complete response prediction may be improved through subtype-specific contrast enhancement thresholds. A validation study is underway with a larger patient population.

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