What is Prostate Cancer?
Prostate cancer occurs when cells grow abnormally in the prostate gland to form tumors. The prostate is a walnut-sized gland located in front of the rectum and under the bladder that secretes the fluid that carries sperm.
Prostate cancer is the most common cancer in men, excluding skin cancer. About 240,890 new cases were expected to be diagnosed in 2011, according to the American Cancer Society (ACS). Fortunately, prostate cancer has a very high success rate when discovered early.
More than 90 percent of all prostate cancers are discovered while they are either localized (confined to the prostate) or regional (nearby). The five-year survival rate for men diagnosed with prostate tumors discovered at these stages is nearly 100 percent.
Choosing an experienced physician and the right cancer center can maximize your chances of a successful outcome and help preserve your quality of life, including sexual function. At Stanford, our Urologic Cancer team includes leading prostate cancer specialists who have extensive experience treating early-stage to advanced prostate cancers.
Prostate Cancer Symptoms
There are usually no specific signs or symptoms of early prostate cancer. A prostate-specific antigen (PSA) blood test and digital rectal exam (DRE) can provide the best chance of identifying prostate cancer in its earliest stages, but these tests can have drawbacks. Talk to your physician about whether prostate cancer screening is right for you.
The following are the most common symptoms of prostate cancer. However, each individual may experience symptoms differently.
Symptoms may include:
- weak or interrupted flow of urine
- urinating often (especially at night)
- difficulty urinating or holding back urine
- inability to urinate
- pain or burning when urinating
- blood in the urine or semen
- nagging pain in the back, hips, or pelvis
- painful ejaculation
The symptoms of prostate cancer may resemble other conditions or medical problems. Always consult your physician for a diagnosis.
As a man gets older, his prostate may grow bigger and obstruct the flow of urine, or interfere with sexual function. An enlarged prostate gland – a condition called benign prostatic hyperplasia – may require treatment with medicine or surgery to relieve symptoms. This common benign prostate condition, which is not cancer, can cause many of the same symptoms as prostate cancer.
Prostate Cancer Risk Factors
In general, all men are at risk for prostate cancer. However, there are specific risk factors that increase the likelihood that certain men will develop the disease, including the following:
Age is a risk factor for prostate cancer, especially men age 50 and older. Nearly two-thirds of all prostate cancers are diagnosed in men over the age of 65.
Prostate cancer is more common among African American men than it is among Caucasian American men. Japanese and Chinese men native to their country have the lowest rates of prostate cancer. When Chinese and Japanese men immigrate to the US, they have an increased risk and mortality rate from prostate cancer, when compared to their native populations. In Japan, the incidence of prostate cancer has increased as Western diets and lifestyles have been adopted.
Epidemiological data suggests that the diet consumed in Western industrialized countries may be one of the most important contributory factors for developing prostate cancer.
Studies suggest that men who eat a high-fat diet, especially if it is high in animal fat, may have a greater chance of developing prostate cancer.
- fruits and vegetables
Diets high in fruits and vegetables may lower prostate cancer risk, although it is not clear which nutrient(s) may be responsible for this. Researchers at Stanford have shown that curciferous vegetables like broccoli might protect against prostate cancer through a chemical called sulforaphane, found at a high level in these vegetables.
- vitamin E and selenium
Vitamin E, an antioxidant, combined with selenium, has been shown to inhibit tumor growth in laboratory animals. However, a large clinical trial found no reduced risk in people who took vitamin E or selenium supplements (or both).
Carotenoids containing lycopenes have been shown to inhibit the growth of human prostate cancer cells in tissue cultures (cells grown in the laboratory). The primary source of lycopenes is processed tomatoes in tomato juice and tomato paste.
Obesity may not raise the risk of prostate cancer, but it has been linked with a higher risk of getting a more aggressive type of prostate cancer.
- environmental exposures
Some studies show an increased chance for prostate cancer in men who are farmers, or those exposed to the metal cadmium while making batteries, welding, or electroplating. Additional research is needed in this area to confirm whether this is a true association.
- having a vasectomy, BPH (benign prostatic hyperplasia), or STD (sexually transmitted disease)
Researchers have looked at whether men who have had a vasectomy, BPH, or those who have been exposed to a sexually transmitted disease are at increased risk for prostate cancer. Some studies suggest a link, while others do not support these claims.
- family history
Having a father or brother with prostate cancer more than doubles a man’s risk of developing this disease. The risk is even higher for men with several affected relatives, particularly if the relatives were young at the time of diagnosis. Geneticists divide families into three groups, depending upon the number of men with prostate cancer and their ages of onset, including the following:
- sporadic – sporadic means ‘occurs by chance’; such as a family with prostate cancer present in one man, at a typical age of onset.
- familial – a family with prostate cancer present in more than one person, but with no definitive pattern of inheritance and usually an older age of onset.
- hereditary – a family with a cluster of three or more affected relatives within any nuclear family (parents and their children), a family with prostate cancer in each of three generations on either the mother or father’s side, or a cluster of two relatives affected at a young age (55 or less). Five percent to 10 percent of prostate cancer cases are considered hereditary. Researchers at Stanford have made important contributions to understanding hereditary prostate cancer.
- genetic factors
Some genes, when altered or mutated, give a higher risk for uncontrolled cell growth, which, in turn, can lead to tumor development. These genes have various names, but overall are referred to as “cancer susceptibility genes.” Approximately 5 percent to 10 percent of all prostate cancers are known to be attributed to an inherited DNA change, such as a cancer susceptibility gene.
Diagnosing Prostate Cancer
In addition to regular physical examinations that include blood, urine, and possibly other laboratory tests, many groups such as the American Cancer Society suggest talking with your doctor to learn more about the pros and cons of screening for prostate cancer to help you decide if it is right for you. The tests used for screening include:
- DRE (digital rectal examination)
A doctor or nurse places a gloved and lubricated finger into the rectum to examine the rectum and feel the prostate gland. DREs may be conducted annually for men over the age of 50 who choose to be screened. Men in high-risk groups, such as African Americans, or those with a strong family history of prostate cancer, should consult their physician about being tested at a younger age or more often.
- PSA (prostate-specific antigen)
PSA is a blood test that measures the level of prostate specific antigen. The use of PSA in clinical practice was pioneered here at Stanford. PSA is a substance produced by the prostate gland, which may be found in higher amounts in men who have prostate cancer. The PSA test may be done annually for men over the age of 50 who choose to be screened. Men in high-risk groups, such as African Americans, or those with a strong family history of prostate cancer, should consult their physician about being tested at a younger age or more often.
If the results of the DRE or PSA are unusual, your doctor may repeat the tests or request other procedures. These evaluation tools may include:
- Magnetic Resonance Imaging (MRI)—a diagnostic test that uses a combination of large magnets, radio frequencies, and a computer to produce detailed images of organs and structures within the body.
- Transrectal Ultrasound (TRUS)—test using sound wave echoes to create an image of the prostate gland to visually inspect for abnormal conditions. A transrectal ultrasound can show if the prostate gland is enlarged or if there are any growths in or around the prostate. Ultrasound may also be used to guide a needle for biopsies of the prostate gland and/or to guide the nitrogen probes in cryosurgery.
- Prostate Biopsy—a test in which where the doctor inserts thin, hollow needles into the prostate to get samples for examination under a microscope to determine if cancer cells are present. The methods of prostate biopsy were developed by Stanford researchers.
- MRI-ultrasound fusion prostate biopsy– a diagnostic test that combines images from MRI and ultrasound to guide tissue collection during prostate biopsy. Using MRI and ultrasound together in real time allows the doctor to target areas that appear most likely to contain tumor cells. Research shows the MRI-ultrasound fusion method can increase the chance of detecting prostate cancer. Your doctor may recommend it if you have had a negative biopsy result but continue to have a high PSA level. Stanford is one of a handful of cancer centers where this new technology is available.
- Computed Tomography Scan (CT or CAT scan)—a diagnostic imaging procedure test that uses a combination of X-rays and computer technology to produce cross-sectional images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than standard X-rays.
- Radionuclide Bone Scan—a nuclear imaging method that helps to show whether the cancer has spread from the prostate gland to the bones. The test involves injecting a radioactive material into a vein that helps to locate diseased bone cells throughout the entire body.
- Lymph Node Biopsy—a procedure in which tissue samples are removed (with a needle or during surgery) from the lymph nodes for examination under a microscope; to determine if cancer or other abnormal cells are present.
Prostate Cancer Staging/Grading
Determining the extent of prostate cancer is important for predicting the course of the disease and in choosing the best treatment. The TNM (tumor, nodes, metastasis) staging system is used to describe a cancer’s clinical stage, or how far it has spread.
T categories (clinical)
There are 4 categories for describing the local extent of a prostate tumor, ranging from T1 to T4. Most of these have subcategories as well.
T1:Your doctor can’t feel the tumor or see it with imaging such as transrectal ultrasound.
- T1a: Cancer is found incidentally (by accident) during a transurethral resection of the prostate (TURP) that was done for benign prostatic hyperplasia (BPH). Cancer is in no more than 5% of the tissue removed and low grade (Gleason Grade 3+3=6 or less).
- T1b:Canceris found during a TURP but is in more than 5% of the tissue removed or is Gleason grade 7 or above.
- T1c:Cancer is found by needle biopsy that was done because of an increased PSA.
T2: Your doctor can feel the cancer with a digital rectal exam (DRE) or see it with imaging such as transrectal ultrasound, but it still appears to be confined to the prostate gland.
- T2a: The cancer is in one half or less of only one side (left or right) of your prostate.
- T2b: The cancer is in more than half of only one side (left or right) of your prostate.
- T2c: The cancer is in both sides of your prostate.
T3:The cancer has begun to grow and spread outside your prostate and may have spread into the seminal vesicles.
- T3a: The cancer extends outside the prostate but not to the seminal vesicles.
- T3b: The cancer has spread to the seminal vesicles.
T4: The cancer has grown into tissues next to your prostate (other than the seminal vesicles), such as the urethral sphincter (muscle that helps control urination), the rectum, the bladder, and/or the wall of the pelvis.
N categories describe whether the cancer has spread to nearby (regional) lymph nodes.
NX: Nearby lymph nodes were not assessed.
N0: The cancer has not spread to any nearby lymph nodes.
N1: The cancer has spread to one or more nearby lymph nodes in the pelvis.
M categories describe whether the cancer has spread to distant parts of the body. The most common sites of prostate cancer spread are to the bones and to distant lymph nodes, although it can also spread to other organs, such as the lungs and liver.
M0: The cancer has not spread past nearby lymph nodes.
M1: The cancer has spread beyond the nearby lymph nodes.
- M1a: The cancer has spread to distant (outside of the pelvis) lymph nodes.
- M1b:The cancer has spread to the bones.
- M1c:The cancer has spread to other organs such as lungs, liver, or brain (with or without spread to the bones).
The Gleason grading system is used to help evaluate the prognosis of men with prostate cancer. Together with other parameters, it is incorporated into a strategy of prostate cancer staging which predicts prognosis and helps guide therapy. A Gleason score is given to prostate cancer based upon its microscopic appearance. Cancers with a higher Gleason score are more aggressive and have a worse prognosis.
The urologist or radiologist performs a prostate needle biopsy, in which a cylindrical sample of prostate tissue is removed through the rectum, using hollow needles, and prepares microscope slides. After a prostate is removed in surgery, a pathologist will slice the prostate for a final examination.
Grades and scores
The pathologist assigns a grade to the most common tumor pattern, and a second grade to the next most common tumor pattern. The two grades are added together to get a Gleason Score.
Traditional Gleason scoring uses a 1-5 scale. However, updated guidelines state that
patterns 1 and 2 should be rarely used if ever, and these numbers are no longer typically assigned in typical prostate needle biopsies. The lowest Gleason grade assigned in clinical practice is 3+3=6.
Research at Stanford has demonstrated that the amount of Gleason pattern 4 in the cancer is indicative of cancer aggressiveness. Therefore a Gleason 3+4=7 cancer is less aggressive than a Gleason 4+3=7 cancer, even though their sum is the same.