CTC enumeration has been found to correlate well with progression free survival (PFS) and overall survival (OS) in prostate cancer patients (Armstrong et al., 2012; Diamond et al., 2012; Miyamoto et al., 2014; Pantel et al., 2019), and has been reported to outperform the traditional prostate cancer monitoring approach using serum PSA (De Bono et al., 2008). The gene discussed is KLK3; the disease is Familial prostate cancer.