Quantitating whole lesion tumor biology in rectal cancer MRI: taking a lesson from FDG-PET tumor metrics
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To determine the value of novel whole tumor metrics in DWI-MRI and DCE-MRI of rectal cancer treatment assessment.
Materials and methods
This retrospective study included 24 uniformly treated patients with rectal adenocarcinoma who underwent MRI including diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) sequences, before and after chemoradiotherapy. Two experienced readers independently measured tumor volume and apparent diffusion coefficient (ADC) on DWI-MRI and tumor volume and transfer constant K trans on DCE-MRI. In addition, we explored and defined Total Lesion Diffusion (TLD) as Total DWI tumor volume multiplied by mean volumetric ADC and Total Lesion Perfusion (TLP) as the total DCE tumor volume multiplied by the mean volumetric K trans. These metrics were correlated with histopathologic percent tumor regression in the resected specimen (%TR). Inter-reader agreement was assessed using the concordance correlation coefficient (CCC).
For both readers, post-treatment TLP revealed comparable correlations with %TR compared with K trans (reader 1; Spearman’s rho = − 0.36 vs. − 0.32, reader 2; Spearman’s rho = − 0.32 vs. − 0.28). In addition, TLP afforded the highest inter-reader agreement at post-treatment among TLP, DCE vol, and K trans (CCC: 0.64 vs. 0.36 vs. 0.35). Post-treatment TLD showed similar correlation with %TR as DWI volume in reader 1 and superior correlation with %TR for reader 2 (reader 1; Spearman’s rho − 0.56 vs. − 0.57, reader 2; Spearman’s rho − 0.59 vs. − 0.45).
The novel tumor metrics TLD and TLP revealed similar results to established metrics for correlation with tumor response with equivalent or superior inter-reader agreements and we recommend that these be studied in larger trials.
KeywordsRectal cancer Tumor response Diffusion-weighted MRI Dynamic contrast-enhanced MRI
We would like to thank our editor, Ada Muellner, MS, for her help with manuscript preparation.
Compliance with ethical standards
Research reported in this publication was supported by the National Cancer Institute of the National Institutes of Health under Award Number R25CA020449. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Conflict of interest
Marc J. Gollub have no disclosures to make, Andreas M. Hötker have no disclosures to make. Kaitlin M. Woo have no disclosures. Yousef Mazaheri have no disclosures. Mithat Gonen Research reported in this publication was supported by the National Cancer Institute of the National Institutes of Health under Award Number R25CA020449. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
The need for informed consent was deemed unnecessary by the Memorial Sloan Kettering IRB and was thus waived for this retrospective study.
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