Prostate Cancer
Among men in the United States, prostate cancer is the most common cancer and the second most common cause of cancer death. The chance of developing prostate cancer increases with age and is greater for African-Americans and Hispanics, men whose close relatives had the disease, and men receiving testosterone treatment. Prostate cancer usually grows very slowly and may take decades to produce symptoms. Thus, far more men have prostate cancer than die from it. Many men with prostate cancer die without ever knowing that the cancer was present.
Prostate cancer begins as a small bump in the gland. Most prostate cancers grow very slowly and never cause symptoms. Some, however, grow rapidly or spread outside the prostate. The cause of prostate cancer is not known.
Symptoms
Prostate cancer usually causes no symptoms until it reaches an advanced stage. Sometimes, symptoms similar to those of benign prostatic hyperplasia (BPH) develop, including difficulty urinating and a need to urinate frequently or urgently. However, these symptoms do not develop until after the cancer grows large enough to compress the urethra and partially block the flow of urine. Later, prostate cancer may cause bloody urine or a sudden inability to urinate.
In some men, symptoms of prostate cancer develop after it spreads (metastasizes). The areas most often affected by cancer spread are bone (typically the pelvis, ribs, or vertebrae) and the kidneys. Bone cancer tends to be painful and may weaken the bone enough for it to easily fracture. Prostate cancer can also spread to the brain, which eventually causes seizures, confusion, headaches, weakness, or other neurologic symptoms. Spread to the spinal cord, which is also common, can cause pain, numbness, weakness, or incontinence. After the cancer spreads, anemia is common.
Screening
Because prostate cancer is common, many doctors check for it in men with no symptoms (screening). However, experts disagree about whether screening is helpful. In theory, screening offers the advantage of finding more prostate cancers early--when the disease is most easily cured. However, because prostate cancer grows so slowly and often never causes symptoms or death, determining the advantages of screening (and thus early treatment) is difficult. Screening may find cancers that would probably not hurt or kill a man even if they were never detected. Treating such a cancer can prove more damaging than leaving the cancer untreated. It is not clear whether the benefits of screening outweigh the harm from unnecessary treatment and testing. Additionally, screening often indicates the possibility of prostate cancer in men without the disease. When screening indicates the possibility of disease, more tests are done to find the cancer. These further tests are expensive, sometimes harmful, and often stressful.
To screen for prostate cancer, a doctor performs a blood test and a digital rectal examination. If the man has prostate cancer, a doctor sometimes feels a lump in the prostate gland. The lump is often hard. A blood test is performed to measure the level of prostate-specific antigen (PSA), a substance that is usually elevated in men with prostate cancer. PSA levels can be misleading: they can be normal when prostate cancer is present or elevated when prostate cancer is absent. PSA levels normally increase with age, but cancer increases the age-related change. Also, PSA levels can be slightly elevated in men with disorders other than prostate cancer (such as BPH or prostatitis) and in men who have undergone procedures involving the urinary tract within the previous 2 days.
Diagnosis
A doctor may suspect prostate cancer based on the man's symptoms or the results of screening tests. The first steps in diagnosing suspected cancer are digital rectal examination and measurement of PSA levels. If results of these tests suggest cancer, ultrasound scanning is usually performed. In men with prostate cancer, ultrasound scans may or may not reveal the cancer.
If the results of a digital rectal examination or PSA test suggest prostate cancer, tissue samples from the prostate are taken and analyzed (biopsy). When performing a biopsy, a doctor usually first obtains images of the prostate by inserting an ultrasound transducer, or probe, into the rectum (transrectal ultrasound). The doctor then obtains tissue samples with a needle inserted through the probe. This procedure takes only a few minutes and may be done with or without local anesthesia.
Two features help a doctor determine the likely course and the best treatment of the cancer: how distorted (malignant) the cells look under a microscope (grading) and how far the cancer has spread (staging).
Grading: Prostate cancer cells that are distorted tend to grow and spread quickly. The Gleason scoring system is the most common way to grade prostate cancer. Based on the microscopic examination and biochemical tests of tissues obtained from the biopsy, a number between 2 and 10 is assigned to the cancer. Scores between 4 and 6 are most common. The higher the number (high grade), the more likely it is that the cancer will spread. Cancers that are confined to a small area within the prostate and have Gleason scores of 5 or lower (low grade) rarely kill a man within 15 years of diagnosis. This is true regardless of the man's age. In contrast, up to 80% of men die within 15 years if the Gleason score is higher than 7. Large, low-grade cancers are more aggressive and may require treatment.
Staging: Testing to stage the cancer often proceeds when cancer is diagnosed. However, such testing may not be necessary when the likelihood of spread beyond the prostate is extremely low.
Prostate cancers are staged according to three criteria: how far the cancer has spread within the prostate, whether the cancer has spread to lymph nodes in areas near the prostate, and whether the cancer has spread to organs far from the prostate. Results of the digital rectal examination, ultrasound scan, and biopsy reveal how far the cancer has spread within the prostate. Computed tomography (CT) or radiolabeled antibody nuclear medicine scans of the pelvis may be performed to detect spread to the lymph nodes, and bone scanning is performed to reveal spread of the cancer to bone. If spread to the brain or spinal cord is suspected, CT or magnetic resonance imaging (MRI) of those organs is performed.
Treatment
Choosing among treatment options can be complicated and often depends on the man's lifestyle preferences. For many men, doctors are uncertain about which treatments are most effective and how likely it is that a particular treatment will prolong a man's life. Some treatments can impair quality of life. For example, major surgery, radiation therapy, and hormonal therapy often cause incontinence and erectile dysfunction (impotence). When choosing among treatment options, men need to weigh the advantages and disadvantages. For these reasons, a man's preferences are a bigger consideration in choosing treatment for prostate cancer than they might be in choosing treatment for many other diseases.
Treatment for prostate cancer usually involves one of three strategies: watchful waiting, curative treatment, and palliative therapy.
Watchful waiting foregoes all treatment until symptoms develop, if they develop at all. This strategy is best for men whose cancers are unlikely to spread or cause symptoms. For example, most cancers that are confined to a small area within the prostate and have low Gleason scores grow very slowly. These cancers usually do not spread for many years. Older men are far more likely to die before such cancers kill them or cause symptoms. Watchful waiting avoids the incontinence and erectile dysfunction associated with many treatments. During watchful waiting, symptoms can be treated if necessary. Periodic testing may also be done to see if the cancer is growing rapidly or spreading. The man may later decide to pursue a cure for the cancer if testing shows growth or spread.
Curative treatment is a common strategy for men with cancers confined to the prostate that are likely to cause troublesome symptoms or death. Such cancers include any that are growing rapidly. Curative (also called definitive) therapy may also help men with small, slowly growing cancers if the man expects to otherwise live many years. Symptoms from such cancers are unlikely to develop in less than a decade and may not do so for 15 or more years. Curative therapy can also benefit men with cancers that have spread outside the prostate and thus are likely to cause symptoms in a relatively short period. However, curative therapy is likely to be successful only with cancers that are still confined to the area near the prostate. Curative therapy can prolong life and reduce or eliminate severe symptoms resulting from some cancers. However, side effects of curative therapy, most significantly permanent erectile dysfunction and incontinence, can impair quality of life.
Palliative therapy aims at treating the symptoms rather than the cancer itself. This strategy is best suited to men with widespread prostate cancer that is not curable. The growth or spread of such cancers can usually be slowed or temporarily reversed, relieving symptoms. Since these treatments cannot cure the cancer, symptoms eventually worsen. Death from the disease eventually follows.
Three forms of treatment can be used to treat prostate cancer: surgery, radiation therapy, and hormonal therapy. Chemotherapy is not usually used.
Surgery: Surgically removing the prostate (prostatectomy) is useful for cancer that is confined to the prostate. Prostatectomy is less effective in curing fast-growing cancers because they are more likely to have spread at the time of diagnosis. Prostatectomy requires general anesthesia, an overnight hospital stay, and a surgical incision, but treatment is accomplished with one procedure. Prostatectomy may lead to permanent erectile dysfunction and urinary incontinence.
There are three forms of prostatectomy: radical prostatectomy, nerve-sparing radical prostatectomy, and laparoscopic radical prostatectomy.
In radical prostatectomy, the entire prostate, the seminal vesicles, and part of the vas deferens are removed. This is the surgery most likely to cure prostate cancer. However, the procedure causes complete incontinence in about 3% of men and partial or stress incontinence in up to 20%. Temporary incontinence develops in most men and may last for several months. Incontinence is less likely in younger men. Erectile dysfunction commonly develops after radical prostatectomy. More than 90% of men with cancer confined to the prostate live at least 10 years after radical prostatectomy. Younger men who can otherwise expect to live at least 10 to 15 more years are most likely to benefit from radical prostatectomy.
Sometimes, depending on the estimated size and location of the cancer, surgery can be performed in such a way that some of the nerves needed to achieve erection are spared--this procedure is called nerve-sparing radical prostatectomy. This procedure cannot be used to treat cancer that has invaded the nerves and blood vessels of the prostate. Nerve-sparing radical prostatectomy is less likely than non-nerve-sparing radical prostatectomy to cause erectile dysfunction.
Another form of prostatectomy is laparoscopic radical prostatectomy. The advantages of this procedure are that it requires a smaller incision and produces less postoperative pain. Disadvantages include increased expense and longer operative time. Because this procedure is technically demanding, it is offered only at certain centers.
Radiation Therapy: The goal of radiation therapy is to kill the cancer and preserve healthy tissue. Radiation may cure cancers that are confined to the prostate, as well as cancers that have invaded tissues around the prostate (but not cancer that has spread to distant organs). Radiation therapy can also relieve the pain resulting from the spread of prostate cancer to bone but cannot cure the cancer itself.
For many stages of prostate cancer, 10-year survival rates with radiation therapy are nearly as high as those achieved with surgery: more than 90% of men with cancer confined to the prostate live at least 10 years after undergoing radiation therapy. Whereas surgery is accomplished in one procedure, radiation therapy usually requires many separate treatment sessions over the course of several weeks.
During traditional radiation therapy, a machine sends beams of radiation to the prostate and surrounding tissues (traditional external beam radiation). A CT scanner is used to identify the prostate and surrounding tissues that are affected by the cancer. Treatments are usually given 5 days per week for 5 to 7 weeks. Although erectile dysfunction can occur in 30% of men, it is less likely to develop after radiation therapy than after prostatectomy. Traditional external beam radiation therapy causes incontinence in fewer than 5% of men. Urethral strictures--scars that narrow the urethra and impede the flow of urine--develop in about 7% of men. Other troublesome but usually temporary side effects of traditional external radiation therapy include burning during urination, having to urinate frequently, blood in the urine, diarrhea that is sometimes bloody, irritation of the rectum and diarrhea (radiation proctitis), and sudden urges to defecate.
With recent technical advances, doctors can more precisely focus the radiation beam on the cancer (a procedure called three-dimensional conformal radiotherapy). Cure rates for traditional external beam radiation and three-dimensional conformal radiotherapy have not yet been compared. However, conformal radiotherapy causes fewer temporary side effects.
Radiation can also be delivered by inserting radioactive implants into the prostate (brachytherapy). The implants are placed using images obtained from ultrasound or CT scans. Brachytherapy offers many advantages: it can deliver high doses of radiation to the prostate while sparing healthy surrounding tissues and producing fewer side effects. Brachytherapy can be performed in a few hours, does not require repeated treatment sessions, and uses only spinal anesthesia. However, brachytherapy may cause urethral strictures in up to 20% of men. Cure rates for brachytherapy have not yet been compared to those from other treatments. Combined treatment with brachytherapy and external beam radiation is sometimes recommended.
Prostate cancer can be resistant to radiation therapy or can recur after treatment.
Hormonal Therapy: Because most prostate cancers require testosterone to grow or spread, treatments that block the effects of this hormone (hormonal therapy) can slow progression of the tumors. Hormonal therapy is commonly used to delay the spread of the cancer or to treat widespread (metastatic) prostate cancer and is sometimes combined with other treatments. Growth and spread of metastatic prostate cancer can be slowed or temporarily reversed with hormonal therapy. Hormonal therapy can prolong life as well as improve symptoms. Eventually, however, hormonal therapy becomes ineffective, and the disease progresses.
Drugs used to treat prostate cancer in the United States include leuprolide and goserelin, which prevent the pituitary gland from stimulating the testes to make testosterone. These drugs are administered by injection in a doctor's office every 1, 3, 4, or 12 months, usually for the rest of the man's life.
Drugs that block testosterone's effects (such as flutamide, bicalutamide, and nilutamide) may also be used. These drugs are taken daily by mouth. However, drugs that block testosterone produce changes associated with low testosterone levels, such as hot flashes, osteoporosis, loss of energy, reduced muscle mass, fluid weight gain, reduced libido, reduced body hair, and often erectile dysfunction and breast enlargement (gynecomastia).
The oldest form of hormonal therapy involves the removal of both testes (bilateral orchiectomy). The effects of bilateral orchiectomy on testosterone level are equivalent to those produced by leuprolide and goserelin. Bilateral orchiectomy greatly slows the growth of the prostate cancer but produces the side effects of low testosterone levels. The physical and psychologic effects of bilateral orchiectomy make the procedure difficult for some men to accept.
Hormonal therapy usually becomes ineffective within 3 to 5 years in men with widespread prostate cancer. When cancer eventually progresses despite hormonal therapy, most men die within 1 or 2 years. When hormonal therapy fails (hormone resistance), alternative hormone drugs or chemotherapy may be tried.
After all forms of treatment, PSA levels are measured at regular intervals depending on the risk for recurrence and the time from treatment completion (usually every 3 to 4 months for the first year, every 6 months for the next year, and then every year for the rest of the man's life). Increases in the PSA levels may indicate that the cancer has recurred.
 See the table Common Methods and Strategies for Treating Prostate Cancer.
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