Impact of third-line treatment with irinotecan plus cetuximab on non-tumor standardized uptake values in patients with metastatic colorectal cancer

Abstract

The correct interpretation of metabolic response in cancer cells to therapy requires knowledge of how tumor free tissue responds to the same treatment. The aim of this study was to evaluate standardized uptake values (SUVs) in tumor free regions of patients with metastatic colorectal cancer prior to and following therapy, via the use of 18-fluoride fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography/computed tomography (PET/CT). On baseline 18F-FDG PET/CT scans (n=51), volumes of interest (VOI) were obtained from tumor-free tissue (aortic arch, liver and spleen) and SUVs normalized to total body mass were registered. The procedure was repeated for a follow-up scan two weeks following a single administration of the third-line treatment with irinotecan plus cetuximab. The mean differences in SUV prior to and following therapy were non-significant (P>0.05) in all the registered tumor-free regions. Correlation coefficients indicated a significant result between the variables (0.74-0.84; P<0.001). This study suggests that the early assessment of metabolic response may be made following the administration of third-line therapy with irinotecan plus cetuximab in patients with metastatic colorectal cancer refractory to second-line treatment with irinotecan.