Clinical significance of monitoring KRAS in tissue and plasma of pancreatic cancer patients.

Abstract

254 Background: KRAS mutation is observed in 90% of pancreatic cancer patients. Therefore, investigating tumor DNA in plasma by KRAS monitoring may be even more valuable in pancreatic cancer patients. Methods: We collected the tissue and plasma of 78 pancreatic cancer patients (surgery group; 39, non-surgery group; 39). KRAS mutation in the tissue and mutated circulating tumor DNA (MctDNA) in plasma was detected by digital polymerase chain reaction in 78 patients. Identical KRAS mutation detected in tissue (ex. 12D, 12V) was monitored in plasma. Results: KRAS mutation in the tissue was detected in 65 of 73 patients. KRAS assessment in the tissue was not performed in 5 patients, because of tissues small amounts of tissue materials by biopsy. These 65 patients with KRAS mutation in tissue showed poorer prognosis (3 years OS; 23.4%) than 8 patients without mutation (3 years; 66.7%). MctDNA in plasma of surgery group was seen in 14 of 39 patients. Thirteen in 14 patients with MctDNA showed recurrence and 12 patients were dead. These 14 patients with MctDNA in plasma showed significantly poorer prognosis (2 years OS; 16.3%) than 25 patients without mutation (3 years; 71.6%) (p = 0.00). Univariate analysis revealed that poor differentiation and the detection of MctDNA were independent factors to predict poor survival in surgery group. The detection of MctDNA was confirmed to be an independent factor in multivariate analysis (Hazard ratio; 31.25). MctDNA in plasma of non-surgery group was seen in 28 of 39 patients. But, MctDNA in 6 patients was disappeared in clinical course. These 6 patients and 11 patients without MctDNA displayed better prognosis (2 years OS; 72.1%) than 22 patients with MctDNA (2 years OS; 12.1%) with significance (p = 0.0001). Univariate and multivariate analysis revealed that no treatment and the detection of MctDNA were independent factors to predict poor survival in non-surgery group. (Hazard ratio; 8.78, 4.76, respectively). Conclusions: KRAS monitoring in plasma reflects tumor dynamics. The appearance of MctDNA during KRAS monitoring provides important information for the treatment of pancreatic cancer patients.