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Reproducibility of Perfusion Parameters in Dynamic Contrast-Enhanced MRI of Lung and Liver Tumors: Effect on Estimates of Patient Sample Size in Clinical Trials and on Individual Patient Responses

¹ Department of Radiology, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Unit 368, Houston, TX 77030.
² Pfizer Inc., Groton, CT.
³ Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX.
⁴ VirtualScopics Inc., Pittsford, NY.
⁵ Department of Radiology, University of Wisconsin, Madison, WI.
⁶ Department of Medical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX.
⁷ Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, TX.

OBJECTIVE. Dynamic contrast-enhanced MRI (DCE-MRI) is a potentially useful noninvasive technique for assessing tissue perfusion, particularly in the context of solid tumors and targeted antiangiogenic and antivascular therapies. Our aim was to determine the reproducibility of perfusion parameters derived at DCE-MRI of tumors of the lung and liver, the most common sites of metastasis.

SUBJECTS AND METHODS. Patients with lung and liver tumors underwent two sequential DCE-MRI examinations 2–7 days apart without any intervening therapy. The volume transfer constant between blood plasma and the extravascular extracellular space (K^trans) and blood-normalized initial area under the signal intensity–time curve (initial AUC_BN) were computed with a two-compartment pharmacokinetic model. Differences in parameters were assessed with within-patient coefficients of variation.

RESULTS. Twenty-three patients had evaluable tumors (12 lung, 11 liver). The within-patient coefficients of variation for K^trans and initial AUC_BN for liver lesions were 8.9% and 9.9% and for lung lesions were 17.9% and 18.2%. Sample sizes for reductions in these parameters from 10% to 50% were estimated to range from two to 102 subjects. Estimates of confidence that changes observed in a given patient were due to intervening therapy rather than variability of the technique were calculated to range from 71% to 87% if a 20% reduction in a parameter was observed.

CONCLUSION. The rate of reproducibility of DCE-MRI parameters is in the range of 10%–20% and is influenced by lesion location, parameters being significantly more reproducible in the liver than in the lung. These findings provide the foundation for interpretation of results and design of clinical trials in which DCE-MRI studies are used to assess objective responses.

Keywords: dynamic contrast-enhanced MRI • liver tumors • lung tumors • reproducibility • solid tumors

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