Correlation between KRAS mutation and 18 F-FDG uptake in stage IV colorectal cancer.

PURPOSE: The purpose of this study is to evaluate the correlation between KRAS mutation, 18 F-FDG uptake, and metastatic pattern in advanced stage colorectal cancer (CRC) patients.

METHODS: Medical records of stage IV CRC patients who underwent 18 F-FDG PET/CT for staging and KRAS mutation analysis were selected. On PET scans, a volume of interest (VOI) was drawn on the primary lesion. 18 F-FDG indices (SUVmax, SUVmean, MTV, TLG) of the primary lesions were obtained and correlated with KRAS mutation of the primary lesion. Also, metastatic sites were recorded. Association between metastatic pattern and KRAS expression and FDG indices were analyzed.

RESULTS: KRAS mutation was positive in 40 (43%) patients. Evaluation of FDG indices showed that higher SUVmax (14.0 vs. 11.2, p = 0.004), higher SUVmean (5.3 vs. 4.7, p = 0.005), and higher TLG (301.4 vs. 205.5, p = 0.023) were predictive of KRAS mutation compared to wild-type (WT) KRAS. Lung metastasis was more frequently involved in patients with KRAS mutation (50.0% vs. 22.6%, p = 0.006), and liver metastasis was more frequently involved in patients with WT KRAS (81.1% vs. 55.0%, p = 0.007). Multivariate analysis showed that  primary tumor location (OR 3.92, p = 0.07) and KRAS mutation (OR 2.45, p = 0.09) were significant factors in lung metastasis model.

CONCLUSION: KRAS mutation patients had more frequent lung metastasis and had higher 18 F-FDG uptake compared to WT KRAS in stage IV CRC.