Correlation of perfusion MRI and .sup.18F-FDG PET imaging biomarkers for monitoring regorafenib therapy in experimental colon carcinomas with immunohistochemical validation

• Published in: PloS one Vol. 10; no. 2
• Main Authors: Eschbach, Ralf S, Fendler, Wolfgang P, Kazmierczak, Philipp M, Hacker, Marcus, Rominger, Axel, Carlsen, Janette, Hirner-Eppeneder, Heidrun, Schuster, Jessica, Moser, Matthias, Havla, Lukas, Schneider, Moritz J, Ingrisch, Michael, Spaeth, Lukas, Reiser, Maximilian F, Nikolaou, Konstantin, Cyran, Clemens C
• Format: Journal Article
• Language: English
• Published: Public Library of Science 10.02.2015
• Subjects: Care and treatment; Colon cancer; Complications and side effects; Health aspects; Immunohistochemistry; Magnetic resonance imaging; Regorafenib; Germany
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0115543

To investigate a multimodal, multiparametric perfusion MRI / .sup.18 F-fluoro-deoxyglucose-(.sup.18 F-FDG)-PET imaging protocol for monitoring regorafenib therapy effects on experimental colorectal adenocarcinomas in rats with immunohistochemical validation. Human colorectal adenocarcinoma xenografts (HT-29) were implanted subcutaneously in n = 17 (n = 10 therapy group; n = 7 control group) female athymic nude rats (Hsd:RH-Foxn1.sup.rnu). Animals were imaged at baseline and after a one-week daily treatment protocol with regorafenib (10 mg/kg bodyweight) using a multimodal, multiparametric perfusion MRI/.sup.18 F-FDG-PET imaging protocol. In perfusion MRI, quantitative parameters of plasma flow (PF, mL/100 mL/min), plasma volume (PV, %) and endothelial permeability-surface area product (PS, mL/100 mL/min) were calculated. In .sup.18 F-FDG-PET, tumor-to-background-ratio (TTB) was calculated. Perfusion MRI parameters were correlated with TTB and immunohistochemical assessments of tumor microvascular density (CD-31) and cell proliferation (Ki-67). Regorafenib significantly (p<0.01) suppressed PF (81.1±7.5 to 50.6±16.0 mL/100mL/min), PV (12.1±3.6 to 7.5±1.6%) and PS (13.6±3.2 to 7.9±2.3 mL/100mL/min) as well as TTB (3.4±0.6 to 1.9±1.1) between baseline and day 7. Immunohistochemistry revealed significantly (p<0.03) lower tumor microvascular density (CD-31, 7.0±2.4 vs. 16.1±5.9) and tumor cell proliferation (Ki-67, 434.0 ± 62.9 vs. 663.0 ± 98.3) in the therapy group. Perfusion MRI parameters [DELTA]PF, [DELTA]PV and [DELTA]PS showed strong and significant (r = 0.67-0.78; p<0.01) correlations to the PET parameter [DELTA]TTB and significant correlations (r = 0.57-0.67; p<0.03) to immunohistochemical Ki-67 as well as to CD-31-stainings (r = 0.49-0.55; p<0.05). A multimodal, multiparametric perfusion MRI/PET imaging protocol allowed for non-invasive monitoring of regorafenib therapy effects on experimental colorectal adenocarcinomas in vivo with significant correlations between perfusion MRI parameters and .sup.18 F-FDG-PET validated by immunohistochemistry.