The Prognostic Value of ¹⁸F-FDG PET/CT and KRAS Mutation in Colorectal Cancers

Prognostic effect of KRAS mutation and side of tumor in colorectal cancer is a highly controversial subject. Therefore, we evaluated the association between FDG uptake pattern in ¹⁸F-fluoro-2-deoxy-glucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) imaging and KRAS mutation and tumor localization in patients with a diagnosis of colon cancer and assessed the effects of these three factors on prognosis and survival.

Eighty-three patients with colorectal cancer were retrospectively included in this study. ¹⁸F-FDG PET/CT study was performed for pretreatment staging. The maximum standardized uptake value (SUV_max) of the primary tumor and survival data of patients were compared between groups. KRAS mutations were detected with the help of real-time Polymerase Chain Reaction technique through genomic DNA extracted from paraffin-embedded tumor tissue blocks. Tumor lesions with potential KRAS mutations were classified as mutant KRAS and wild type.

Twenty five patients were female while 58 were male. The mean age of the patients was 59.8±11.3 years. Mean follow-up was 35.5±18.9 months. Primary tumor was localized in the left colon in 83.1% of patients and in the right colon in 16.9%. KRAS mutation was detected in 54.2% (n=45) of patients. Mean SUV_max of patients with primary tumor was estimated to be 21.1±9.1 (range= 6.0-47.5). Mean tumor SUV_max of patients with a KRAS mutation (24.0±9.0) was found to be significantly higher than those without KRAS mutation (17.7±8.2) (p=0.001). Mean survival was significantly shorter in patients with locoregional nodal metastasis than in patients without locoregional nodal metastasis as well as in patients with distant nodal metastasis than in patients without distant nodal metastasis and in patients with organ metastasis in initial PET/CT than in patients without organ metastasis. Also, mean survival was nearly statistically-significantly shorter in patients with tumors located in left colon (34.2±19.4) than in right colon (43.2±14.6) (p=0.059). However, we found no significant impact of KRAS mutation on survival.

In our study, we found that tumor localization had no significant effect on prognosis in patients with colon cancer. On the other hand, FDG uptake was observed to be higher in the presence of KRAS mutation and it was concluded that coexistence of KRAS mutation with higher SUV_max is a negative prognostic factor.