The cancer diagnosed most often among men in the United States, striking about one of every 11 Caucasian men and one of every nine African-American men. The diagnosis is usually made at age 70 or older, but many older men will develop “silent” prostate cancer that produces few (if any) symptoms and does not affect life expectancy.
Prostate cancer incidence has been increasing rapidly in recent years, probably because of the greater use of prostate cancer screening — especially the widespread introduction of the prostate-specific antigen blood test. As yet, however, there is little medical consensus about prostate cancer’s cause, recommendations for screening, or usefulness of early detection and treatment.
Prostate cancer is the most common solid tumor among American men, and is the second leading cause of cancer deaths in the United States; about 220,000 new cases of prostate cancer are diagnosed each year in the United States. Because most prostate cancers are tiny, have not spread, and do not cause symptoms, another 9 million American men may have prostate cancer without knowing it.
The incidence rates for prostate cancer, which is rare before age 50, have been particularly high in the developed areas of the world, such as North America, Europe, Australia, and New Zealand. These high incidence rates may, in part, reflect better cancer detection strategies.
Prostate cancer develops from cells inside the prostate gland, found near the neck of the bladder, which produces part of the fluid of semen. When cells in the prostate become malignant, they remain within the gland in about a third of all men as they grow older. In many cases, decades pass before this limited type of cancer spreads beyond the prostate gland’s tough outer shell. Before they spread, up to 90 percent of these cancers can be cured with local treatment, such as radical prostatectomy (surgical removal of the prostate gland) or radiation therapy.
However, if cancer grows beyond the prostate gland, it may invade surrounding parts of the bladder and urethra, causing urinary problems. The cancer also may spread to nearby lymph nodes, or to the bones, liver, or rectum. Cancers that have spread to lymph nodes or other organs generally are not curable, although they often can be controlled for a number of years with proper treatment.
In early stages, prostate cancer rarely causes symptoms. Typically it grows very slowly, and some of the symptoms linked to enlargement of the prostate are also the same as for benign prostatic hypbrplasia (BPH). If the prostate cancer spreads into the urethra or bladder neck, it can cause the following problems:
• Urinary problems
• Decreased force of the urine stream
• Frequent urination and intense need to urinate
• Inability to urinate
• Repeated urinary tract infections
• Presence of blood in the urine or semen
• Weight loss
• Aches and pains
If prostate cancer spreads to the bones, it may cause continual or intermittent bone pain that may be located in just one area or may move around the body. More common sites for spread of prostate cancer to the bones include the ribs, hips, back, and shoulders. Because some of these sites are also common areas for the development of arthritis, determining the cause of the pain can be difficult. Significant weakening of the bones may lead to fractures.
Prostate cancer also may spread to the lymph nodes or other organs; it can cause swollen glands, weight loss, anemia, and shortness of breath. Cancer that has spread to the spine may cause paralysis if the nerves become compressed. If the cancer grows into the bladder or affects most of the pelvic lymph nodes, it may obstruct one or both of the ureters that drain urine from the kidneys into the bladder. This obstruction may cause a drop in urine volume (or total absence of urine if both ureters are blocked), back pain, nausea and vomiting, and sometimes fever.
The goal of prostate cancer screening is to find this malignancy while it is still at the early, curable stage. However, experts disagree about whether all men should be screened routinely for prostate cancer, since prostate abnormalities are common and because in many cases prostate cancer never threatens a man’s life. Nevertheless, regular screening does greatly increase the chance that prostate cancer will be detected at an early stage; for this reason, many experts recommend that prostate screening be performed once a year for all men except those who have a very low baseline prostate-specific antigen (PSA) level (below 2), who may want to consider screening every other year. The American Cancer Society recommends that all men be offered routine screening for prostate cancer starting at age 50 and that African-American men consider screening at age 45.
The best way to screen for prostate cancer is a combination of a digital rectal exam (DRE) of the prostate and a blood test known as the prostate-specific antigen blood test (PSA test). PSA is a protein produced by the prostate and normally secreted into the semen; in prostate cancer (and some other prostate disorders) large amounts of PSA can leak out of the prostate, raising PSA level in the blood. In the DRE test, a doctor inserts an index finger into the rectum and gently feels the surface of the prostate through the rectal wall to check for lumps, hardness, and enlargement.
The combination PSA-DRE is important because men who have a normal PSA level may have prostate cancer; if a rectal exam reveals a firm area, a biopsy should be performed. Only about 10 percent of prostate cancers are found by a DRE (in the setting of a normal PSA finding). Most healthcare providers and Medicare cover annual DREs and PSA tests for qualified Medicare patients older than age 50.
Patients should tell the doctor if they are using any prescription or over-the-counter medication to treat an enlarged prostate. Certain prostate medications, such as finasteride (Proscar) or saw palmetto, can affect the results of the PSA test.
In addition, a doctor usually takes a personal medical history, including a history of any non-cancerous condition of the prostate, such as inflammation or enlargement, and any history of prostate cancer in first-degree relatives.
If a man’s PSA level is high or the DRE result is abnormal, the doctor orders a biopsy of the prostate, usually performed while guided by a transrectal ultrasound. In the biopsy, tissue is removed from the top, middle, and bottom of the gland on both sides or from any suspicious areas identified by DRE or ultrasound. In order to lessen the pain and discomfort associated with performing prostate biopsies dramatically, the surgeon uses a nerve block identical to that injected by dentists. After the nerve block is performed, a thumb-sized probe is placed into the rectum and the ultrasound measures the size of the prostate and locates the areas for biopsy. Eight to 12 biopsy specimens are taken, depending on the size of the prostate, and sent to a pathologist. The results are sent to the urologist within a week.
Depending on the biopsy results, PSA level, physical findings, and family history of prostate cancer, a doctor may order additional tests to determine whether the cancer has spread to the lymph nodes, bones, or other sites. These tests may include a computed tomography scan, magnetic resonance imaging scan, or bone scan. However, if a patient has a PSA level less than 10 and a Gleason score of 6 or less, there appears to be no need for a bone scan, CT scan, or an MRI, since spread of the cancer is virtually never observed in those circumstances. For all other patients, the urologist decides on the appropriate test as indicated by the PSA level and Gleason score.
Sometimes, prostate cancer may be discovered when a pathologist examines tissue removed during a transurethral prostatectomy (TURP) for an enlarged prostate (benign prostate hyperplasia) . This is becoming more rare as TURP is less common due to the success of medical therapy for BPH.
The most common way to determine how likely the prostate cancer is to grow and spread quickly is to grade the cancer by using the gleason grading system.
If prostate cancer is diagnosed, the laboratory assesses how abnormal the cancer cells look and assigns a Gleason score to the tumor; the score ranges from 1 (low grade) to 5 (high grade). The grade of prostate cancer cells describes the appearance of the cells, whether they are aggressive and very abnormal (high grade) or not aggressive or barely abnormal (low grade). The grade of the cancer is an important factor in predicting long-term results of treatment and survival.
Prostate cancer may have cells of different grades, so the pathologist assigns numbers to the two most common types present, ranging from 1 to 5. A Gleason score is the total of these two numbers; for example, a man who has a Gleason grade of 3 and 4 has a Gleason score of 7. Low-score cancers are those with a Gleason score of 2, 3, or 4; intermediate-score cancers are those with a Gleason score of 5, 6, or 7; high-score cancers have a Gleason score of 8, 9 or 10.
Classifying the tumor by using the TNM system indicates whether — or how far — the cancer has spread. In the TNM system, the T stands for tumor; it classifies a growth on the basis of its size, its location on one or both sides of the prostate, and its spread beyond the gland into other parts of the body. The tumor is given a numerical score ranging from the least dangerous (T1) through the most dangerous (T4). The classifications are further divided into (a), (b), and (c) categories. T1, T1a, T1b, T1c, T2, T2a, T2b, or T2c is considered a “local” cancer: It has not spread beyond the prostate. T3, T3a, or T3b refers to cancer that has spread just slightly beyond the prostate, but not into other organs or throughout the body. T4 (there are no initialed subcategories) describes the most advanced type of prostate cancer, which has spread to other organs or throughout the body.
The N part of the TNM system is an assessment of whether the tumor has spread to the lymph nodes in the pelvis. This classification is either NO (no contamination of the lymph nodes) to N1 (has spread into the lymph nodes). The last part of the TNM staging system is used to assess whether the tumor has spread (metastasized) beyond the lymph nodes in the pelvis. There are four categories, ranging from MO (has not spread) to M1a (has spread into lymph nodes beyond the pelvis), M1b (has spread to the bones), to M1 (has spread to other parts of the body besides bones and lymph nodes).
Side Effects of Treatment
Men who undergo treatment for prostate cancer must be prepared for the possibility of urinary incontinence or a decline in their ability to have an erection. Urinary problems may result after damage to the urethra during treatment for prostate cancer, because the urethra runs through the prostate. This incontinence may be temporary or permanent.
Impotence may be caused by damage to the bundle of nerves responsible for erection that run along each side of the prostate. Eventually, a man’s sexual potency may return to normal, depending on his health and age. Fortunately there are several treatments from which to choose that may help restore erections, including medications such as sildenafil (viagra), vacuum devices, and penile prosthetic implants.
However, recent studies have found that most men who are treated for early prostate cancer are satisfied with their treatment decision. After radical prostatectomy or androgen deprivation therapy (ADT), Hispanic men are less satisfied than non-Hispanic white men. Men who after treatment were cancer free, had urinary and bowel control, could have erectile function (65.9 percent), had good general health (71.3 percent), and preserved social relationships (68.1 percent) were significantly associated with being satisfied with treatment choice. Men who received no active treatment were less satisfied (50.5 percent) than actively treated men, and Hispanic men were less satisfied than non-Hispanic Caucasian men after undergoing radical prostatectomy (50.1 percent versus 58.0 percent) or androgen deprivation therapy (29.7 percent versus 71.8 percent). The majority of men were satisfied with their treatment selection for clinically localized prostate carcinoma. Receiving an active treatment, believing oneself to be free of cancer, having no treatment complications, and having good overall health and social support were positively associated with satisfaction.
The American cancer society recommends that men limit intake of high-fat foods from animal sources and eat five or more servings of fruits and vegetables each day. Several factors may help prevent the development of prostate cancer, including eating a low-fat diet, getting lots of exercise, and taking certain medications. A man may be able to decrease the risk for prostate cancer by eating a low-fat diet high in vitamin E, selenium, and natural antioxidants such as lycopene. Helpful foods include tofu and soy milk, tomatoes, green tea, strawberries, raspberries, blueberries, red grapes, peas, watermelon, rosemary, garlic, and citrus fruits.
Vitamin E may reduce prostate cancer risk, according to a recent study of more than 29,000 men in Finland. About half of the men took 50 mg of vitamin E daily, and this group experienced 32 percent fewer cases of prostate cancer than men who did not take vitamin E supplements. Foods rich in vitamin E include vegetable oils, particularly those from safflower, sunflower, and cotton seeds; wheat germ and whole grains; and whole nuts, such as almonds. Currently, however, doctors do not recommend vitamin E or selenium supplements to decrease prostate cancer risk.
Getting lots of exercise appears to lower risk of developing prostate cancer.
The drug finasteride (Proscar) reduced the risk of prostate cancer by nearly 25 percent, according to a June 2003 report that represented the culmination of three decades of research that began in the early 1970s at University of Texas Southwestern Medical Center. The study, reported in The New England Journal of Medicine, showed that finasteride, which is already proved effective as a therapy for enlarged prostate, also delays or prevents prostate cancer and reduces the risk of urinary problems. However, the drug has significant sexual side effects and may increase the risk of high-grade prostate cancer in some patients, the study reports.
Finasteride inhibits the conversion of testosterone to dihydrotestosterone by the enzyme 5-alpha-reductase. By doing so, it reduces by 90 percent the level of dihydrotestosterone (the primary androgen in the prostate that is involved in the development of prostate cancer). The findings are the result of the Prostate Cancer Prevention Trial, a seven-year study of 9,457 men.