• David C Newitt, Zheng Zhang, Jessica E Gibbs, Savannah C Partridge, Thomas L Chenevert, Mark A Rosen, Patrick J Bolan, Helga S Marques, Sheye Aliu, Wen Li, Lisa Cimino, Bonnie N Joe, Heidi Umphrey, Haydee Ojeda-Fournier, Basak Dogan, Karen Oh, Hiroyuki Abe, Jennifer Drukteinis, Laura J Esserman, Nola M Hylton, and ACRIN Trial Team and I-SPY 2 TRIAL Investigators.
• Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
• J Magn Reson Imaging. 2019 Jun 1; 49 (6): 1617-1628.

BackgroundQuantitative diffusion-weighted imaging (DWI) MRI is a promising technique for cancer characterization and treatment monitoring. Knowledge of the reproducibility of DWI metrics in breast tumors is necessary to apply DWI as a clinical biomarker.PurposeTo evaluate the repeatability and reproducibility of breast tumor apparent diffusion coefficient (ADC) in a multi-institution clinical trial setting, using standardized DWI protocols and quality assurance (QA) procedures.Study TypeProspective.SubjectsIn all, 89 women from nine institutions undergoing neoadjuvant chemotherapy for invasive breast cancer.Field Strength/SequenceDWI was acquired before and after patient repositioning using a four b-value, single-shot echo-planar sequence at 1.5T or 3.0T.AssessmentA QA procedure by trained operators assessed artifacts, fat suppression, and signal-to-noise ratio, and determine study analyzability. Mean tumor ADC was measured via manual segmentation of the multislice tumor region referencing DWI and contrast-enhanced images. Twenty cases were evaluated multiple times to assess intra- and interoperator variability. Segmentation similarity was assessed via the Sørenson-Dice similarity coefficient.Statistical TestsRepeatability and reproducibility were evaluated using within-subject coefficient of variation (wCV), intraclass correlation coefficient (ICC), agreement index (AI), and repeatability coefficient (RC). Correlations were measured by Pearson's correlation coefficients.ResultsIn all, 71 cases (80%) passed QA evaluation: 44 at 1.5T, 27 at 3.0T; 60 pretreatment, 11 after 3 weeks of taxane-based treatment. ADC repeatability was excellent: wCV = 4.8% (95% confidence interval [CI] 4.0, 5.7%), ICC = 0.97 (95% CI 0.95, 0.98), AI = 0.83 (95% CI 0.76, 0.87), and RC = 0.16 * 10-3 mm2 /sec (95% CI 0.13, 0.19). The results were similar across field strengths and timepoint subgroups. Reproducibility was excellent: interreader ICC = 0.92 (95% CI 0.80, 0.97) and intrareader ICC = 0.91 (95% CI 0.78, 0.96).Data ConclusionBreast tumor ADC can be measured with excellent repeatability and reproducibility in a multi-institution setting using a standardized protocol and QA procedure. Improvements to DWI image quality could reduce loss of data in clinical trials.Level Of Evidence2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:1617-1628.© 2018 International Society for Magnetic Resonance in Medicine.

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