KLK3 and cancer: An observational study by Ried et al. [46] involving 600 CTCs tests on 542 patients showed that these cells were detected in 100% of cancer patients (n = 277) and 50% of asymptomatic patients with risk factors (132 out of 265), with follow-up scans identifying early cancerous lesions in 20% of screened patients and early prostate cancer in 50% of males with normal prostate specific antigen (PSA) levels but positive CTCs results, highlighting the value of CTCs analysis for early detection and monitoring.