The COBAS Epidermal Growth Factor Receptor (EGFR) mutation assay (Non-small lung cancer), therascreen PIK3CA RGQ PCR Kit, BRACAnalysis (Breast and Ovarian cancer) and methylation profile of SEPT9 gene (Colorectal cancer) have been approved for ctDNA-based companion diagnostic assays and several assays are also being developed for use with immuno-oncology-based therapies (Yan et al., 2021). Here, EGFR is linked to ovarian cancer.