Where does prostate cancer spread?
As the prostate cancer grows, it grows through the prostate, the prostate capsule, and the fat that surrounds the prostate capsule. Because the prostate gland lies below the bladder and attaches to it, the prostate cancer can also grow up into the base of the bladder.
Prostate cancer can also grow into the seminal vesicles, which are located adjacent to the prostate. It may continue to grow locally in the pelvis into muscles within the pelvis; into the rectum, which lies behind the prostate; or into the sidewall of the pelvis. The spread of cancer to other sites is called metastasis. When prostate cancer spreads outside of the capsule and the fatty tissue, it usually goes to two main areas in the body: the lymph nodes that drain the prostate and the bones. The more commonly involved lymph nodes are those in the pelvis (Figure 5), and bones that are more
Figure 5. Lymph node drainage from the prostate.
From Prostate and Cancer by Sheldon H.F. Marks. Copyright © 1995 by Sheldon Marks. Reprinted with permission of Perseus Books Publishers, a member of Perseus Books, LLC.
commonly affected are the spine (backbones) and the ribs. Less commonly, prostate cancer can spread to solid organs in the body, such as the liver.
What is prostate cancer screening?
The goal of any screening is to evaluate populations of people in an effort to diagnose the disease early. Thus, the goal of prostate cancer screening is the early detection of prostate cancer, ideally at the curable stage. Prostate cancer screening includes both a digital rectal examination and a serum PSA. Each of these is important in the screening process, and an abnormality in either warrants further evaluation. Only about 25% of prostate cancers are revealed by rectal examination; most are detected by an abnormal PSA. Some studies suggest that even with PSA-based prostate cancer screening, up to 15% of men will have undetected prostate cancer. Newer screening tools, such as EPCA and EPCA-2, are being investigated (see Question 6).
Because the prostate gland lies in front of the rectum, the back wall of the prostate gland can be felt by putting a gloved, lubricated finger into the rectum and feeling the prostate by pressing on the anterior wall of the rectum (Figure 6). The rectal examination allows one to feel only the back of the prostate. Ideally, the same doctor should perform the rectal examination each year so that the doctor is able to detect subtle changes in your prostate. The exam can be performed by an urologist or by an experienced primary care provider. If the primary care provider is concerned about your examination, you will be referred to a urologist. On rectal examination, the examiner is checking the prostate for a nodule. A prostate nodule is a firm, hard area in the prostate that feels like the knuckle of your finger. A prostate nodule may be cancerous and should be biopsied, but not all prostate nodules are cancers. Other causes of a nodule
Figure 6. Digital rectal examination of the prostate.
or a firm area in the prostate include prostatitis (prostate infection or inflammation), prostate calculi, an old infarct in the prostate, or abnormalities of the rectum, such as a hemorrhoid. If you have had your rectum removed, then your doctor will rely on the PSA. If the PSA were to rise significantly, then a prostate biopsy would be performed. A transrectal ultrasound biopsy likewise cannot be performed in individuals without a rectum. In this situation, the biopsy is performed transperineally, which means through the perineum (the area under the scrotum). Performing biopsies in this way can be more uncomfortable, and they are often performed with some form of anesthesia (general, spinal, or intravenous sedation).
Prostate cancer screening should be performed on a yearly basis, except for men with a very low initial PSA level who may want to consider screening every other year. As you continue with screening on a yearly basis, changes in the PSA (beyond what is believed to be a change caused by benign growth of the prostate) or rectal examination will prompt further evaluation. It is hoped that, through the use of prostate cancer screening, the morbidity and mortality associated with prostate cancer will be diminished. More recent studies are showing increased survival as a result of prostate cancer screening.
Historically, the American Urologie Association and the American College of Surgeons recommend that most men start prostate cancer screening at the age of 50 years. Men with a family history of prostate cancer and African Americans should begin screening at age 40 years. In April 2009, the American Urologic Association issued new guidelines lowering the age for beginning prostate-specific antigen (PSA) and digital rectal examination (DRE) screening to 40 years for relatively healthy, well-informed men who wanted to be tested.
Prostate cancer screening is of maximal benefit for men who are going to live long enough to experience the benefits of treatment, typically, survival for at least 10 years from the diagnosis of prostate cancer. Thus, if you have medical conditions that make survival of 10 additional years less likely, you probably would not benefit from the early detection and treatment of prostate cancer and could stop prostate cancer screening. In addition, if you feel that you would not want any treatment for prostate cancer regardless of your age and overall health, then you should stop prostate cancer screening.
A combination of PSA and a digital rectal examination is the best screening for prostate cancer.