Detection of KRAS mutations in circulating tumor cells from patients with metastatic colorectal cancer

Abstract

Background: Quantification of Circulating Tumor Cells (CTCs) as a prognostic marker in metastatic colorectal cancer (mCRC) has already been validated and approved for routine use. However, more than quantification, qualification or characterization of CTCs is gaining importance, since the genetic characterization of CTCs may reflect, in a real time fashion, genetic profile of the disease. Objective: To characterize KRAS mutations (codon 12 and 13) in CTCs from patients with mCRC and to compare with matched primary tumor. Additionally, correlate these mutations with clinical and pathological features of patients. Methods: Blood samples were collected from 26 patients with mCRC from the AC Camargo Cancer Center (São Paulo-Brazil). CTCs were isolated by ISET technology (Isolation by Size of Epithelial Tumors; Rarecells Diagnostics, France) and mutations analyzes were performed by pyrosequencing (QIAGEN). Results: KRAS mutation was detected in 7 of the 21 cases (33%) of samples from CTCs. In matched primary tumors, 9 of the 24 cases (37.5%) were found KRAS mutated. We observed that 5 of the 9 samples with KRAS mutation in their primary tumor had also KRAS mutation in CTCs, meaning a concordance of 71% of matched cases (P D 0.017). KRAS mutation neither on primary tumor nor in CTCs was associated with clinical-pathological parameters analyzed. Conclusion: Faced with a polyclonal disease like colorectal cancer, which is often treated with alternating and successive lines of chemotherapy, real time genetic characterization of CTCs, in a fast and feasible fashion, can provide important information to clinical management of metastatic patients. Although our cohort was limited, it was possible to show a high grade of concordance between primary tumor and CTCs, which suggests that CTCs can be used as surrogate of primary tumors in clinical practice, when the knowledge of mutation profile is necessary and the primary tumor is not available.

Correlation between epidermal growth factor receptor tyrosine kinase inhibitor efficacy and circulating tumor cell levels in patients with advanced non-small cell lung cancer

“…Counting was made per milliliter of blood. Cells were considered CTCs if they were negative for CD45 and presented with hyperchromatic nucleus, irregular shape, and high cytoplasm–nucleus ratio (>0.5) 9. Positive results for peripheral blood micrometastases were defined as CTCs ≥5/7.5 mL 6…”

Technological advances in precision medicine and drug development

“…More novel is the use of CTCs for personalized treatments [29]. In a variety of cancers, mutation analysis for common variants in CTCs is being evaluated to assist in treatment selection [30,31]. While still exploratory, this avenue is gaining recognition in the medical research community.…”

Circulating Tumor Cells Versus Circulating Tumor DNA in Colorectal Cancer: Pros and Cons

“…It is unclear at this time if this heterogeneity affects outcomes, but it is possible that failure of EGFR-inhibition in patients thought to have a KRAS wild-type CRC (determined from an arbitrary section of the primary tumor) may be partly due to the presence of a KRAS -mutated subclonal population. In a recent study, Buim et al demonstrated that KRAS mutations derived from CTCs correlate with mutations in the primary tumor with a concordance of 71 % of matched cases ( P = 0.017) [61]. These studies suggest that CTCs may play a role as a surrogate for primary tumors and metastasis when genomic analysis is necessary and the primary tumor is not available or as a means to serially monitor tumor genomes that can evolve during relapse, treatment, and progression.…”