Prostate cancer is the most common type of cancer in men in the United States (other than skin cancer), and accounts for more than one-quarter of all men diagnosed with cancer each year.
The prostate is a gland in the male reproductive
system, which makes and stores seminal fluid, a milky fluid that nourishes sperm
and is released to from part of semen.
The prostate gland is about the size of a walnut, and surrounds the upper part of the urethra, the tube that empties urine from the bladder. If the prostate gland grows too large, the flow of urine can be slowed or stopped.
What is Prostate Cancer?
Cancer is a group of many related diseases that begin in cells, the body's basic unit of life. The body is made up of many types of cells, and normally, cells grow and divide to produce more cells only when the body needs them. Sometimes, however, cells keep dividing when new cells are not needed. These extra cells form a mass of tissue, called a growth or tumor. There are two types of tumor, benign and malignant.
Benign tumors are not cancer. They can usually be removed, and in most cases, they do not come back. Cells from benign tumors do not spread to other parts of the body and are not a threat to life. Benign prostatic hyperplasia (BPH) is the abnormal growth of benign prostate cells. In BPH, the prostate grows larger and presses against the urethra and bladder, interfering with the normal flow of urine. More than half of the men in the United States between the ages of 60 and 70 have symptoms of BPH. For some men, the symptoms may be severe enough to require treatment.
Malignant tumors are cancer. Cells in these tumors are abnormal, they divide without control or order, and can invade and damage nearby tissues and organs. Cancer cells can break away from a malignant tumor and enter the bloodstream or the lymphatic system, which is how cancer spreads from the original cancer site to form new tumors in other organs. The spread of cancer is called metastasis.
When prostate cancer spreads (metastasizes) outside the prostate, cancer cells are often found in nearby lymph nodes and possibly other parts of the body (other lymph nodes and other organs, such as the bones, bladder, or rectum). When cancer spreads from its original location to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if prostate cancer spreads to the bones, the cancer cells in the new tumor are prostate cancer cells. The disease is metastatic prostate cancer, not bone cancer.
What causes Prostate Cancer?
The causes of prostate cancer are not well understood. There are a number of risk factors associated with prostate cancer:
- Age -- In the United States, prostate cancer is found mainly in men over age 55. The average age of patients at the time of diagnosis is 70.
- Family history of prostate cancer -- The risk for developing prostate cancer is higher if a close relative (father or brother) has had the disease.
- Race -- Prostate cancer is much more common in African American men than in white men. It is less common in Asian and Native American men.
- Diet and dietary factors -- A diet high in animal fat may increase the risk of prostate cancer and a diet high in fruits and vegetables may decrease the risk. Studies are in progress to learn whether men can reduce their risk of prostate cancer by taking certain dietary supplements.
There is very little evidence that a vasectomy, BPH, obesity, lack of exercise, smoking, radiation exposure, or a sexually transmitted virus might increase the risk for prostate cancer.
Detecting Prostate Abnormalities
The following tests are used to detect prostate abnormalities, but they cannot show whether abnormalities are cancer or another, less serious condition. The doctor will take the results into account in deciding whether to check the patient further for signs of cancer.
Digital rectal exam involves the doctor inserting a lubricated, gloved finger into the rectum to feel the prostate through the rectal wall and to check for hard or lumpy areas.
Blood test for Prostate-Specific Antigen (PSA) -- The level of PSA may rise in men who have prostate cancer, BPH, or infection in the prostate.
Symptoms of Prostate Cancer
Early prostate cancer often does not cause symptoms. But prostate cancer can cause any of these problems:
- A need to urinate frequently, especially at night
- Difficulty starting urination or holding back urine
- Inability to urinate
- Weak or interrupted flow of urine
- Painful or burning urination
- Difficulty in having an erection
- Painful ejaculation
- Blood in urine or semen; or
- Frequent pain or stiffness in the lower back, hips, or upper thighs.
Any of these symptoms may be caused by cancer or by other, less serious health problems, such as BPH or an infection. A man who has symptoms like these should see his doctor or urologist.
Diagnosing Prostate Cancer
If symptoms or test results suggest prostate cancer, the doctor checks personal and family medical histories, will perform a physical exam, and may order laboratory tests. The exams and tests may include a digital rectal exam, a urine test to check for blood or infection, and a blood test to measure PSA. In some cases, the level of prostatic acid phosphatase (PAP) in the blood will be checked, especially if the results of the PSA indicate there might be a problem.
Other exams the doctor may order include:
- Transrectal Ultrasonograpy -- Ultrasound waves are sent out by a probe inserted into the rectum, the waves bounce off the prostate, and a computer uses the echoes to create a picture called a sonogram.
- Intravenous pyelogram is a series of x-rays of the organs of the urinary tract.
- Cystoscopy is a procedure in which a doctor looks into the urethra and bladder through a thin, lighted tube.
- Biopsy is ordered if test results suggest that cancer is present. During a biopsy, the doctor removes tissue samples from the prostate, usually with a needle. A pathologist looks at the tissue under a microscope to check for cancer cells. If cancer is present, the tumor will be graded. The grade tells how much the tumor tissue differs from normal prostate tissue and suggests how fast the tumor is likely to grow.
If the test results do not suggest cancer, the doctor may recommend medicine to reduce the symptoms caused by an enlarged prostate, or surgery. The surgery most often used in such cases is called transurethral resection of the prostate (TURP or TUR). In TURP, an instrument is inserted through the urethra to remove prostate tissue that is pressing against the upper part of the urethra and restricting the flow of urine.
Stages of Prostate Cancer
If cancer is found in the prostate, the doctor needs to know the stage, or extent, of the disease. Staging is a careful attempt to find out whether the cancer has spread and, if so, what parts of the body are affected. The doctor may use various blood and imaging tests to learn the stage of the disease. Treatment decisions depend on these results.
Prostate cancer staging is a complex process. The doctor may describe the stage using a Roman number (I-IV) or a capital letter (A-D). These are the main features of each stage:
- Stage I / Stage A -- The tumor cannot be felt during a rectal exam. There is no evidence that the cancer has spread outside the prostate.
- Stage II / Stage B -- The tumor can be felt during a rectal exam, or is found with a biopsy that was performed because of a high PSA level. There is no evidence that the cancer has spread outside the prostate.
- Stage III / Stage C -- The cancer has spread outside the prostate to nearby tissues.
- Stage IV / Stage D -- The cancer has spread to lymph nodes or to other parts of the body.
Methods of Treatment and Side Effects
Treatment for prostate cancer depends on the stage of the disease and the grade of the tumor. Other important factors are the man's age, general health and his feelings about the treatments and possible side effects. Prostate cancer can be managed in a number of ways:
Watchful Waiting may be suggested for some men who have prostate cancer that is found at an early stage and appears to be slow growing, and for older men or men with other serious medical problems where the risks and possible side effects of surgery, radiation therapy, or hormonal therapy may outweigh the possible benefits.
Although men who choose watchful waiting avoid the side effects of surgery and radiation, there can be some negative aspects to this choice. Watchful waiting may reduce the chance of controlling the disease before it spreads, and older men should keep in mind that it may be harder to manage surgery and radiation therapy as they age.
Surgery is a common treatment for early stage prostate cancer. The doctor may remove all of the prostate (radical prostatectomy) or only part of it:
- In radical retropubic prostatectomy, the doctor removes the entire prostate and nearby lymph nodes through an incision in the abdomen.
- In radical perineal prostatectomy, the doctor removes the entire prostate through an incision between the scrotum and the anus. Nearby lymph nodes are sometimes removed through a separate incision in the abdomen.
- In transurethral resection of the prostate (TURP), the doctor removes part of the prostate with an instrument that is inserted through the urethra. The cancer is cut from the prostate by electricity passing through a small wire loop on the end of the instrument. This method is used mainly to remove tissue that blocks urine flow.
If cancer cells are found in the lymph nodes, it is likely that the disease has spread to other parts of the body. Sometimes, the lymph nodes are removed before doing a prostatectomy. If the prostate cancer has not spread to the lymph nodes, the prostate is removed, but if cancer has spread to the nodes, usually the prostate is not removed and other treatment will be suggested.
For the first few days after surgery, pain will usually need to be controlled with pain relief. A catheter will be inserted into the urethra to drain urine. It is also common to experience tiredness and weakness. Surgery to remove the prostate may cause long-term problems, including rectal injury, urinary incontinence and impotence.
Radiation therapy (called radiotherapy) uses high-energy x-rays to kill cancer cells. Like surgery, radiation therapy is local therapy and it can affect cancer cells only in the treated area. In early stage prostate cancer, radiation can be used instead of surgery, or it may be used after surgery to destroy any cancer cells that may remain in the area. In advanced stages, it may be given to relieve pain or treat other problems.
Radiation may be directed at the body by a machine (external radiation), or it may come from tiny radioactive seeds placed inside or near the tumor (internal or implant radiation, or brachytherapy). Men who receive radioactive seeds alone usually have small tumors. Some men with prostate cancer receive both kinds of radiation therapy.
Radiation therapy may cause patients to become extremely tired, especially in the later weeks of treatment. Some men may also experience diarrhea or frequent and uncomfortable urination. External radiation therapy may cause the treated area of skin to become red, dry and tender and can also cause hair loss. Both types of radiation therapy can cause impotence, but internal radiation therapy is not as likely to cause nerve damage. Internal radiation therapy may cause temporary incontinence.
Hormonal therapy deprives cancer cells from getting the male hormones they need to grow. It is called systemic therapy because it can affect cancer cells throughout the body. Systemic therapy is used to treat cancer that has spread and is sometimes used to prevent the cancer from coming back after surgery or radiation treatment.
There are several forms of hormonal therapy:
- Orchiectomy is surgery to remove the testicles, which are the main source of male hormones.
- Drugs known as luteinizing hormone-releasing hormone (LH-RH) agonists can prevent the testicles from producing testosterone. Examples are leuprolide, goserelin, and buserelin.
- Drugs known as antiandrogens can block the action of androgens. Examples are flutamide and bicalutamide.
- Drugs that can prevent the adrenal glands from making androgens include ketoconazole and aminoglutethimide.
After orchiectomy or treatment with an LH-RH agonist, the body no longer gets testosterone from the testicles. However, the adrenal glands still produce small amounts of male hormones. Sometimes, the patient is also given an antiandrogen, which blocks the effect of any remaining male hormones. This combination of treatments is known as total androgen blockade.
Prostate cancer that has spread to other parts of the body usually can be controlled with hormonal therapy for a period of time, often several years. Eventually, however, most prostate cancers are able to grow with very little or no male hormones. When this happens, hormonal therapy is no longer effective, and other forms of treatment may be suggested.
The side effects of hormonal therapy depend largely on the type of treatment. Orchiectomy and LH-RH agonists often cause side effects such as impotence, hot flashes, and loss of sexual desire. Antiandrogens can cause nausea, vomiting, diarrhea, or breast growth or tenderness. If used for a long time, ketoconazole may cause liver problems, and aminoglutethimide can cause skin rashes. Men who receive total androgen blockade may experience more side effects than men who receive a single method of hormonal therapy. Any method of hormonal therapy that lowers androgen levels can contribute to weakening of the bones in older men.
Drugs used in the Treatment of Prostate Cancer
- Clinagen LA 40
- conjugated estrogens
- Dep Gynogen
- esterified estrogens
- Estragyn LA 5
- Gynogen LA 20
- Trelstar Depot
Developments in Prevention of Prostate Cancer
Several studies are under way to explore how prostate cancer might be prevented. These include the use of dietary supplements, such as vitamin E and selenium. Recent studies suggest that a diet that regularly includes tomato-based foods may help protect men from prostate cancer.
Researchers also are investigating whether diets that are low in fat and high in soy, fruits, vegetables, and other food products might prevent the recurrence of prostate cancer.
The drug finasteride is being studied in the Prostate Cancer Prevention Trial, which involves thousands of men across the country participating for 7 years, until 2004.
Developments in Treatment of Prostate Cancer
Cryosurgery is under study as an alternative to surgery and radiation therapy. This involves placing an instrument known as a cryoprobe in direct contact with the tumor to freeze it and destroy cancer cells, while avoiding healthy tissue.
There are also studies of new treatment schedules such as the usefulness of hormonal therapy before primary therapy (surgery or radiation) to shrink the tumor.