To detect early prostate cancer in the absence of symptoms and signs, doctors use prostate-specific antigen blood tests and digital rectal exams, reports the American Cancer Society. If either test detects an abnormality, a prostate biopsy is necessary for a definitive diagnosis. Following diagnosis, further blood tests and imaging tests determine how far the cancer has spread, points out MedicineNet.com.
A digital rectal exam involves a doctor inserting a gloved finger into the rectum to feel for prostate cancers growing at the back of the gland, explains the American Cancer Society. In a biopsy, a urologist applies a local anesthetic and uses a needle to remove a tissue sample from the prostate gland, and a pathologist analyzes it to find cancer cells, according to MedicineNet.com. If the biopsy detects cancer, the doctor may conduct imaging tests such as a CT scan, an MRI and a bone scan.
Raised PSA levels detected in a blood test do not always indicate prostate cancer because age, an enlarged prostate, ejaculation, certain medications and other factors can raise PSA levels, explains the American Cancer Society. Other factors such as obesity, herbal mixtures, aspirin and some prescription drugs lower PSA levels. Doctors sometimes measure PSA velocity to register how fast PSA levels are rising and PSA density to compare the PSA reading with the size of the prostate gland.