The prostate is an organ of the male reproductive system. More than 186,000 men in the United States are diagnosed with prostate cancer each year, according to the National Cancer Institute. Prostate cancer is staged I through IV and takes into account whether the cancer has spread, a Gleason score (determined by the shape of the cells under a microscope), and blood PSA level (prostate-specific antigen). Higher Gleason and PSA scores indicate indicate a more severe, higher stage cancer. The purpose of assigning a stage to cancer is to help determine the best course of treatment and to gauge the patient’s prognosis.
Stage I is the earliest stage of prostate cancer. The American Cancer Society reports that the doctor cannot feel the tumor or see it by ultrasound during this stage; or, if it is detectable, the tumor is very small. The presence of prostate cancer is diagnosed based on a biopsy where a sample of the cells is removed and deemed cancerous based on their appearance under a microscope. Stage I prostate cancer has not spread, the Gleason score is 6 or less and the PSA level is below 10.
In the earlier part of stage II prostate cancer (stage IIA), the doctor may still not be able to feel the tumor or see it by ultrasound, but the man’s PSA score is higher than 10 and less than 20, and his Gleason score is six or less; or the PSA level is less than 20, and the Gleason score is seven. The cancer is also in stage IIA if the cancer can be felt by rectal exam or seen by ultrasound, but the PSA score is less than 20, and the Gleason score is seven or less. The cancer is considered to be in the latter part of stage II (stage IIB) if the tumor can be felt by physical exam or seen by ultrasound, with any Gleason score and a PSA score greater than 20; or the Gleason score is eight or higher, regardless of PSA score.
The National Cancer Institute reports that stage III prostate cancer is characterized by the spread of the cancerous cells beyond the prostate into the seminal vesicles. The seminal vesicles are a pair of glands located next to the prostate. However, the cancer has not yet spread to the lymph nodes. The American Cancer Society adds that the PSA score and Gleason score may be any number.
In stage IV prostate cancer, the cancerous cells have spread beyond the seminal vesicles into other organs, such as the bladder, rectum or bones. The cancer may also be detectable in the lymph nodes. When the cancer has spread beyond the prostate, it is called metastatic prostate cancer.
About this Author
Leah DiPlacido, a medical writer with more than nine years of biomedical writing experience, received her doctorate in immunology from Yale University. Her work is published in Journal of Immunology, Arthritis and Rheumatism, and Journal of Experimental Medicine. She writes about disease for doctors, scientists, and the general public.