Study: Serial Liquid Biopsy May Be Useful in Identifying RAS Genetic Mutations in mCRC

Serial liquid biopsies may provide a useful tool for identifying changes in the mutation status of genes in the RAS family in patients with metastatic colorectal cancer (mCRC) who have undergone antiangiogenic therapy, according to a recent study.

Additionally, the retrospective analysis, published in In Vivo, supported the idea that mCRC is an ever-changing condition and that antiangiogenic therapy might induce RAS mutational changes in patients with mCRC.

Approximately 22% of CRCs are diagnosed as metastatic and about 70% of patients will develop metastatic relapse. The arrival of anti-angiogenic chemotherapies and targeted therapies against epidermal growth factor receptor (EGFR) signaling pathways for patients without KRAS mutations has produced better survival rates. However, few studies have investigated the impact of antiangiogenic therapy on the molecular profile of patients with tumors with RAS mutations.

Detecting mutational changes of RAS genes in circulating tumor DNA (ctDNA) derived from blood samples could be a simple and noninvasive alternative to testing of primary tumors and can be conducted at various points in the course of a patient’s cancer.

The investigators collected data on 23 patients with mCRC from the Infanta Sofía University Hospital in Madrid, Spain from June 2018 to June 2019. The mean (SD) age of the patients was 67.3 (9.8) years and 65.2% (n = 15) were men. Stage 4 disease was observed in 78.3% of patients. Computer tomographic scans and assays of ctDNA were performed every 2 months.

Only 1 patient presented microsatellite instability and loss of MSH2 expression. Prior to the liquid biopsy, 21 patients had been treated with bevacizumab (Avastin), 1 received aflibercept (Eylea) therapy, and 1 received both drugs. The median (range) time from initiation of antiangiogenics to the first liquid biopsy was 4 (1-28) months. In total, 17 KRAS mutations and 6 NRAS mutations were observed in primary tumors. No patients carried BRAF mutations.

The first analysis of ctDNA revealed that that RAS mutation status changed to wild-type in 73.9% (n = 17) of patients. RAS oncogene mutations were maintained in 6 patients. Among the 17 patients with wild-type RAS mutations, 3 additional RAS mutations were observed during subsequent ctDNA analysis. However, the status of the mutations returned to their initial status after a median (range) duration of 7 (6-9) months of antiangiogenic therapy. The 2 month gap between sequential liquid biopsies made the investigators unable to determine the precise moment when the status of the RAS mutations changed.

“The fact that 17 out of 23 of our patients experienced a selection of clones with wild-type RAS in our study highlights the importance of performing molecular analysis prior to the administration of further lines of therapies,” noted the investigators.

The investigators listed several study limitations, including the small cohort size, the plausible probability of detecting false-negative mutated tumors due to the assays utilized, and that concomitant therapies may have produced a potential source of bias, making it difficult to distinguish which RAS mutations were induced by prior chemotherapies and which were produced by antiangiogenics therapy.

“Assessment of changes from RAS-mutated to wild-type RAS variants in patients with metastatic CRC and evaluation of anti-EGFR therapy in this context warrants further investigation and prospective randomized studies are required,” wrote the investigators.

Reference

García de Santiago B, López-Gómez M, Delgado-López PD, et al. RAS mutational status in advanced colorectal adenocarcinoma treated with anti-angiogenics: Preliminary experience with liquid biopsy. In Vivo. September-October 2021;35(5):2841-2844. doi: 10.21873/invivo.12571