A combination of the results from a prostate-specific antigen blood test, digital rectal exam and the Gleason score from a biopsy are used to indicate if cancer has spread beyond the prostate, explains the American Cancer Society. If the results indicate the cancer may have spread, imaging tests are requested.
Imaging tests such as computed tomography scans, magnetic resonance imaging and X-rays are used to identify abnormalities in the size and shape of structures in the body, such as the lymph nodes, rectum, bladder or urethral sphincter, explains the American Cancer Society. A contrasting agent might be used with a CT scan to help outline the intestines or other structures, while a probe called an endorectal coil might be utilized during an MRI.
The results of the PSA test are used to help determine the stage of prostate cancer, notes the American Cancer Society. For the cancer to be considered stage 1, the PSA score cannot exceed 10. The doctor may not yet be able to feel it with a digital rectal exam, and it may not appear on a transrectal ultrasound. In stage 2 prostate cancer, the PSA score cannot be higher than 20. At stage 3, the PSA no longer plays a role in staging.