Background: Metastatic colorectal cancer (mCRC) patients with positive KRAS genomic mutations should not receive anti-epidermal growth factor receptor (EGFR) monoclonal antibodies, as stated by the American Society of Clinical Oncology. However, there are some limitations to KRAS mutation testing. Few published studies evaluating the correlation between 18F-FDG PET/CT imaging and KRAS expression in mCRC patients have yielded conflicting results. Aiming to clarify whether 18F-FDG PET/CT scan can be used as a surrogate biomarker for KRAS status in mCRCs in order to optimize treatment strategies, this study explored this relationship.
Patients and Methods: This prospective study included 38 patients (26 males and 12 females) with mCRCs and known KRAS mutational status; all of them underwent pretreatment 18F-FDG PET/CT imaging. Maximum standardized uptake value (SUVmax), total lesion glycolysis (TLG) and metabolic tumor volume (MTV) of metastatic lesions with the highest FDG uptake were analyzed. Results: SUVmax was significantly higher in the mutated KRAS than in the WT-KRAS group (13.1±11.9 vs. 7.01±4.2, respectively; P=0.016). There was an increase in the mean values of MTV and TLG in the KRAS mutant group, albeit without statistical significance (P= 0.450 and 0.908, respectively). Thus, SUVmax was the only PET/CT parameter that could predict KRAS mutations (OR: 1.180, 95% CI: 1.006-1.384; P= 0.041). SUVmax cutoff value of >8.8 (AUC of 0.728) yielded the best accuracy (72.8%), with 58.8% sensitivity and 81.0% specificity in predicting KRAS mutations. Conclusion: The accumulation of 18F-FDG was significantly higher in metastatic lesions of CRCs with positive KRAS mutations. We propose that 18F-FDG PET/CT based SUVmax could be used as a non-invasive surrogate biomarker for KRAS genomic expression in mCRC patients to aid in treatment selection.