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Published on: September 25, 2018
Clonal diversity in KRAS mutant colorectal adenocarcinoma under treatment: Monitoring of cfDNA using reverse
Emese Sarolta Bádon1, Attila Mokánszki1, Anikó Mónus1
1Department of Pathology, Faculty of Medicine, University of Debrecen, H-4032, Debrecen, Hungary.
Abstract:
Biological heterogeneity is a key feature of malignancies that significantly contributes to disease progression and therapy resistance. Residual/relapsed tumor foci may represent genetically divergent subclones, which remain uncovered as repeated and multiple tumor sampling is usually limited. The analysis of circulating free DNA (cfDNA) from the peripheral blood plasma (also called a liquid biopsy, LB) is a new achievement that provides an effective tool for follow-up monitoring of cancer-related genetic status. The present study highlights the phenomenon of mutational variability observed in patients with metastatic KRAS mutant colorectal cancer (mCRC) during treatment with bevacizumab in combination in a longitudinal fashion. The prospective study included 490 mCRC patients evaluated between 2020 and 2022 in our institution. Out of the 211 KRAS mutant cases (43.06%) 12 tumors were identified with multiple KRAS gene variants (5.68%). Detailed follow-up investigations were possible in 3 of these patients including the genotyping of the primary and available metastatic tumors, and the peripheral blood cfDNA. cfDNA was collected from three different time points before and between cycles of combined treatment with bevacizumab chemotherapy. KRAS gene variants were identified using reverse-hybridization strips, and next-generation sequencing (NGS), and confirmed by conventional Sanger sequencing. Interestingly, surgery and multiple treatment cycles reorganized the mutational profiles in the selected cases. The effect of the treatments resulted either in the overrepresentation of one of the pre-existing gene variants or in the appearance of new KRAS variants absent in the primary sample, according to the plasma cfDNA findings. Besides the KRAS variants demonstrated by targeted analysis, NGS mutational profiling identified some additional pathogenic variants from the cfDNA samples (including NRAS and MET alterations). In conclusion, plasma cfDNA sampling enables the monitoring of mutational heterogeneity and subclonal dynamics of the actual metastatic tumor mass in mCRC. The pattern of molecular profile potentially reflects a differential drug response determining further progression.
Insights
Liquid biopsies reveal evolving KRAS mutations in metastatic colorectal cancer (mCRC) during bevacizumab treatment. Plasma cfDNA monitoring tracks tumor heterogeneity and potential drug resistance, guiding further treatment strategies.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Biological heterogeneity in malignancies drives disease progression and therapy resistance.
- Tumor subclones often remain undetected due to limited sampling.
- Circulating free DNA (cfDNA) liquid biopsy offers a non-invasive method for monitoring cancer genetics.
Purpose of the Study:
- To investigate mutational variability in KRAS-mutant colorectal cancer (mCRC) during bevacizumab treatment.
- To assess the utility of plasma cfDNA for longitudinal monitoring of tumor genetic status.
- To explore the dynamics of KRAS variants and other mutations in response to therapy.
Main Methods:
- Prospective study of 490 mCRC patients (2020-2022).
- Genotyping of primary tumors, metastatic sites, and plasma cfDNA using reverse-hybridization, NGS, and Sanger sequencing.
- Longitudinal cfDNA collection at three time points during bevacizumab chemotherapy.
Main Results:
- 12 out of 211 KRAS-mutant mCRC cases (5.68%) exhibited multiple KRAS variants.
- Treatment and surgery altered mutational profiles, leading to overrepresentation of existing variants or emergence of new ones.
- NGS identified additional pathogenic variants (NRAS, MET) in cfDNA beyond KRAS.
Conclusions:
- Plasma cfDNA analysis effectively monitors mutational heterogeneity and subclonal dynamics in mCRC.
- Molecular profiling via cfDNA can indicate differential drug responses and predict disease progression.
- Liquid biopsy provides a valuable tool for real-time assessment of metastatic tumor evolution.
