KRAS mutations by digital PCR in circulating tumor cells isolated from the mesenteric vein are associated with residual disease and overall survival in resected colorectal cancer patients

• Published in: International journal of colorectal disease Vol. 35; no. 5; pp. 805 - 813
• Main Authors: Li, Yan, Monzo, Mariano, Moreno, Isabel, Martinez-Rodenas, Francisco, Hernandez, Raquel, Castellano, Joan J., Canals, Jordi, Han, Bing, Muñoz, Carmen, Navarro, Alfons
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-05-2020; Springer; Springer Nature B.V
• Subjects: Aged; Aged, 80 and over; Analysis; Blood; Care and treatment; Cell Separation; Colorectal cancer; Colorectal carcinoma; Colorectal Neoplasms - genetics; Colorectal Neoplasms - pathology; Colorectal Neoplasms - surgery; Copy number; DNA sequencing; Female; Gastroenterology; Gene Dosage; Genetic aspects; Hepatology; Humans; Internal Medicine; K-Ras protein; Male; Medicine; Medicine & Public Health; Mesenteric Veins - pathology; Metastasis; Middle Aged; Mutants; Mutation; Mutation - genetics; Neoplasm Staging; Neoplasm, Residual - genetics; Neoplasm, Residual - pathology; Neoplastic Cells, Circulating - pathology; Nucleotide sequencing; Original Article; Patient outcomes; Polymerase Chain Reaction - methods; Proctology; Proto-Oncogene Proteins p21(ras) - genetics; Surgery; Survival Analysis; Tumor cells; KRAS mutations; Digital PCR; Circulating tumor cells; Mesenteric vein; Colorectal cancer
• ISSN: 0179-1958; 1432-1262
• DOI: 10.1007/s00384-020-03538-6

Purpose
In colorectal cancer (CRC), circulating tumor cells (CTCs) are released into the mesenteric veins (MV). We chose to determine whether KRAS mutations detected in CTCs from blood obtained at the time of surgery could be a marker of survival.
Methods
From 52 surgically resected CRC patients who later relapsed, samples of tumor tissue, normal tissue, and blood from the peripheral vein (PV) and MV were obtained from each patient at the time of surgery. KRAS mutations were assessed by Sanger sequencing and digital PCR (DGPCR) in tissue samples and by DGPCR in CTCs. Mutant KRAS copy number was assessed in CTCs. Results were correlated with overall survival (OS).
Results
Sanger sequencing detected KRAS mutations in ten tumor samples (19.2%), while DGPCR detected mutations in 30 (58%). Mutations were detected in CTCs in 21 MV samples (40.4%) and 18 PV samples (34.6%). Patients with G13D mutations in CTCs from the MV had shorter OS than those with G12D mutations (28.1 vs 54.6 months;
p
 = 0.025). Patients with a high mutant KRAS copy number in CTCs had shorter OS than those with a low mutant KRAS copy number (MV: 20.5 vs 43.7 months;
p
 = 0.002; PV: 15.1 vs 38.2 months;
p
 = 0.027).
Conclusion
DGPCR is more efficient than Sanger sequencing for detecting KRAS mutations. KRAS G13D mutations and high mutant KRAS copy number are associated with shorter OS. The analysis of KRAS mutations in CTCs from blood obtained at the time of surgery can identify patients with a higher risk of relapse.