Existing cancer screening methods include: (1) the Papanicolau test for women to detect cervical cancer and mammography to detect breast cancer, (2) prostate-specific antigen (PSA) level detection in blood sample for men to detect prostate cancer, (3) occult blood detection for colon cancer, and (4) endoscopy, CT scans, X-ray, ultrasound imaging and MRI for various cancer detection. This evidence concerns the gene KLK3 and prostate cancer.