The relationship between clinical and pathological findings and FDG - PET uptake in metastatic colorectal cancers

In metastatic colorectal cancer (mCRC), the genetic structure and cell metabolism of the primary tumor lesion might be different from metastatic lesions. It is thought that cell-level glucose metabolism may differ due to the difference in RAS wild and mutant mCRC patients' prognosis. In this study, we aimed to compare 2-deoxy-2-[fluorine-18]-fluoro-D-glucose Positron Emission Tomography (18F-FDG PET/CT) uptake levels for KRAS mutation status and primary-metastatic tumor localization.

Our study is a retrospective cohort analysis that included RAS mutation status study and staging-oriented 18F-FDG PET/CT conducted on mCRC patients.

There was no significant relationship between metastasis and primary tumor maximum Standardized uptake value (SUVmax) values according to the KRAS mutational status (P > 0.05). Patients with liver metastasis along with mutant BRAF mutation status had significantly higher SUVmax values in PET-CT scans (P = 0.04). There was a negative correlation between SUVmax values of lung metastases and overall survival (r = -0.35, P = 0.04). Patients with high carcinoembryonic antigen (CEA) levels had significantly higher SUVmax values of lung metastasis than patients with normal CEA levels (P = 0.009). Patients with high CA19-9 levels had significantly higher SUVmax values of liver, peritoneal, and bone metastasis than patients with normal CA19-9 levels (P = 0.002, P = 0.001, P = 0.004, respectively). There was no significant correlation between SUVmax values of metastasis and Lactate dehydrogenase (LDH) values. Liver metastasis of right-sided mCRCs had significantly higher SUVmax values (P = 0.03).

We could not demonstrate a significant association between KRAS mutation and SUVmax values of PET scan in primary or metastatic tumor sites in advanced CRC.