What is Prostate cancer?
In American men, prostate cancer is the most common type of cancer with the exception of skin cancer. It is also one of the deadliest forms of cancer in men, ranking after lung cancer in deaths and usually with a similar number of deaths as colorectal cancers. However, most prostate cancer patients survive the disease and die of unrelated causes. Earlier detection and better treatment have increased the survival rate over recent years.
The prostate is a walnut-size gland that is part of the male reproductive system. The prostate helps produce and distribute seminal fluid, which protects sperm cells in semen. The prostate is located in front of the rectum and below the bladder. It surrounds the upper part of the urethra, the tube that carries urine and semen out of the body through the penis. As men age, the prostate tends to enlarge and restrict the urethra, reducing the flow of urine.
The prostate gland initially develops in the male fetus and continues to grow as the male reaches adulthood. It attains its normal size and function when increased amounts of male hormones are produced at puberty.
The prostate is a gland and nearly all prostate cancers are adenocarcinomas, meaning they begin in the glandular cells. Prostate cancer usually grows slowly. In many cases, particularly in elderly men, the disease does not require treatment, and some men are never even aware they have the disease. This is also more common in elderly men. Sometimes, however, prostate cancer grows quickly. It can spread to the hip, spine and other nearby bones and lymph nodes. It is sometimes difficult for physicians to tell which prostate cancers are dangerous and which do not pose a threat. Less than 5 percent of prostate cancers are of types other than adenocarcinomas. These other types include small cell carcinomas, squamous cell carcinomas, transitional cell carcinomas and prostate sarcomas. Cancers of these types in the prostate may not respond to treatment and usually have a poorer prognosis.
The disease accounts for 10 percent, or about 27,000 of male cancer deaths a year. About one man in six will be diagnosed with prostate cancer, but only 1 man in 34 will die of the disease. According to the ACS:
- 99 percent of men diagnosed with prostate cancer survive it at least five years
- 93 percent survive it at least 10 years
- 77 percent survive it at least 15 years
Race and nationality are also variables. African Americans have a 60 percent higher risk than white and Hispanic Americans of developing prostate cancer, and their prognosis is not as good. Asian Americans and Pacific Islanders are at lower risk. Prostate cancer is more common in North America and northwestern Europe than in other regions of the world. Scientists do not know why the disease is more likely to affect black Americans than white Americans but less likely to affect men in Asia, Africa and South America.
Despite its high survival rate, prostate cancer presents ongoing lifestyle considerations for some patients. Any treatment of prostate cancer may affect the male genital and urinary systems. It may present complications that affect a man's ability to control his bladder, in addition to sexual functioning.
How is it diagnosed?
Signs and symptoms of prostate cancerMany cases of prostate cancer are diagnosed before symptoms appear, through the use of a blood test called the prostate-specific antigen test (PSA). Prostate cancer usually has no symptoms in the early stages and may even lack symptoms in later stages. When symptoms are present, they often are mistaken for other conditions, such as urinary tract or bladder infections or benign enlargement of the prostate.
The prostate surrounds the urethra, the tube through which urine and semen leave the body in men. When symptoms do occur, many are related to urination. These symptoms include increased urge to urinate, weak or interrupted urine flow, pain or burning during urination, blood in the urine and the sensation that the bladder does not empty. Some men may also experience pain during ejaculation.
If the prostate cancer has metastasized (spread) to the bone, patients may have pain, especially in the hips, lower back or upper thighs.
Physical exam: Screening is ordinarily done by feeling the prostate, by inserting a finger into the rectum (digital rectal examination). If a rock-hard nodule is felt, the suspicion of cancer is raised, and the nodule should be biopsied. However, digital examination cannot detect small or early prostatic tumors.
Tests: Prostate-specific antigen (PSA), a protein produced only by the prostate, is a much more sensitive indicator of prostate cancer. By measuring PSA in the blood, even microscopic tumors can be detected. But, PSA is not very specific. It is elevated also in other non-cancerous diseases of the prostate including benign prostatic hypertrophy, a very common disorder, and prostatitis. In general, the higher the PSA level, the more likely that cancer will be found on biopsy.
Transrectal ultrasound (TRUS) is another diagnostic means. TRUS demonstrates the size and location of lesions within the prostate, and can also detect extension of tumor through the capsule. An ultrasound probe is inserted into the rectum, and is used to evaluate the size of the prostate and locate any tumors. Although sensitive, TRUS is not specifically diagnostic for prostate cancer, and is expensive. Therefore, it is seldom used for routine screening. It is used to further evaluate an abnormal digital exam and/or PSA.
In individuals suspected of having prostate cancer, a needle biopsy of the suspicious nodule is done to obtain a definite diagnosis. TRUS may be used during the procedure to guide placement of the biopsy needle, decreasing the likelihood of missing a small tumor.
Microscopic examination of the biopsy specimen not only provides the diagnosis, but also determines the grade of the cancer. Grade refers to the microscopic characteristics and growth pattern of the tumor cells, and is an index of tumor aggressiveness. If the tumor resembles normal prostate tissue microscopically, it is said to be a low-grade cancer and will probably not grow aggressively. A high-grade cancer is more likely to progress more rapidly, invade, or spread to other areas of the body.
Once prostate cancer has been confirmed by biopsy, it is necessary to determine its stage. Stage refers to the extent to which the tumor has spread, and this will influence its treatment. The stage might not be known with certainty until surgery is performed, but other tests can provide useful information.
Elevated serum levels of prostatic acid phosphatase (PAP, a prostatic enzyme) suggest either local extension or metastasis. However, PAP can be misleading, since manipulation of the prostate during digital rectal examination or other procedures can cause transient elevation. Elevated serum alkaline phosphatase and/or serum calcium suggests bone metastasis. Bone scan is the best procedure for detecting bone metastases; plain x-rays can also detect bone metastases, but are most useful when the bone scan is uncertain.
MRI is used to evaluate the prostate, pelvic contents, and lymph node involvement. CT scans are less accurate than MRI for staging prostate cancer, and are not routinely used.
Diagnostic tests are used to monitor progress after treatment. PSA levels should decrease after treatment going to zero when surgery or radiation are potentially curative. Subsequently, a rising PSA signals recurrent tumor growth.
Lymphangiography (a special x-ray of the lymphatic vessels) may be performed in individuals with advanced or high-grade disease with a high likelihood of lymph node involvement.
How is Prostate cancer treated?
There are many approaches to treating prostate cancer. Factors to consider include the severity and extent of the cancer, the man's age and general health, and whether the patient wants to risk side effects of treatment for a possible cure. Some tumors spread quickly and need aggressive therapy. Many other prostate tumors are slow growing and may not need such aggressive treatment.
Several measurements obtained during diagnostic tests may provide some guidelines for treatment. These include the level of prostate-specific antigen and the Gleason score, a measure of the cancer's aggressiveness. In some cases, a combination of treatments, such as surgery followed by radiation therapy, may be used as therapy.
The cure rates for radiation treatments alone and surgical removal of the prostate are similar at 10 years after treatment (about 92 percent for each treatment). Risks of aggressive treatments include the possibility of incontinence or impotence. However, prostate cancer is usually slow to spread and in some cases does not need treatment, especially in the elderly or chronically ill.
The most common treatments are:
“Watchful waiting” (expectant management)This involves regular monitoring of the cancer through tests such as the digital rectal exam and PSA test. Watchful waiting may be used if the cancer has been detected in an early stage or if it is slow growing and confined to a small area of the prostate. It is also used with elderly patients who may not be able to tolerate cancer treatments.
Radical prostatectomySurgical removal of the prostate and nearby tissues. Typically, general anesthesia is used, and the patient is discharged from the hospital after a few days. The incision may be made through the lower abdomen or the perineum, the area between the scrotum and anus. Risks of surgery include blood loss and infection. Following surgery, a narrow flexible tube (catheter) is placed through the urethra into the bladder to move urine through the penis for a few weeks while the area heals. Men usually regain full bladder control within weeks or months. This treatment often cures early prostate cancer.
The potential complications for prostatectomy, which include bladder control problems and sexual dysfunction, are a major concern for most men. According to the American Academy of Family Physicians:
- Patients under age 50 are more likely to retain sexual function afterward.
- Patients over 70 are more likely to become impotent.
- Impotence is less likely if the tumor is small and nerves do not have to be cut.
- Patients rarely have severe incontinence. About one-third have occasional leaking of urine during laughter, coughing or heavy lifting.
Partial prostatectomySurgical removal of part of the prostate. The most common type of partial prostatectomy is called transurethral resection of the prostate (TURP). It is more often a treatment for an enlarged prostate, but it may be performed to relieve pain and ease urination in men with cancer that radical prostatectomy cannot cure.
Radiation therapyUse of high-energy x-rays or radioactive seeds to kill or shrink malignant cells. Radiation therapy is a possible option for prostate cancer that has not spread outside of the prostate gland to distant sites in the body. External beam radiation therapy (EBRT) delivers radiation from an external machine in precise doses targeted at a specific area. Internal radiation (brachytherapy) uses implanted radioactive “seeds” to deliver the radiation to the prostate or nearby areas. Radiation may be used after prostatectomy.
Hormone therapyReduces the level of male hormones to control the growth of cancer. Male hormones (androgens) such as testosterone encourage the growth of many prostate tumors. Hormonal therapy may be used for early stage prostate cancer as well as for cancers that have spread in the body. Hormone therapy may be accomplished with the use of drugs or surgery. Hormone therapy cannot cure prostate cancer but can help shrink the tumor and slow the growth of the cancer.
The drugs used in hormone therapy work in different ways. Some drugs, known as luteinizing hormone-releasing hormones (LH-RH) agonists, help prevent the production testosterone. Other drugs (anti-androgens) work to decrease the body's ability to use testosterone. Patients eventually may become resistant to hormone therapy but intermittent hormone therapy programs may help the effectiveness of treatment. The side effects of hormone therapy may include breast enlargement, hot flashes, reduced sex drive, weight gain, thromboembolism. Some of the drugs may also cause gastrointestinal problems, including nausea and diarrhea, and liver damage. Guidelines for hormone therapy are changing, both in terms of the type of hormone therapy, when to start it and the other risks associated with it. Regular patient-physician consultation about the disease and its treatment course is the best approach for hormone therapy.
Orchiectomy (surgical castration)Surgical version of hormone therapy. This has the same effect as hormone drug therapy but is irreversible. It is usually an outpatient procedure or can involve brief hospitalization. It involves local, spinal or general anesthesia. The surgeon makes an incision in the scrotum to remove the testicles. Prosthetic testicles may be inserted to give the scrotum a normal look. Orchiectomy can cause hot flashes and will cause impotence and loss of interest in sex.
Cryotherapy (also called cryosurgery)Freezing and destruction of prostate cancer cells. This is a newer treatment that uses liquid nitrogen to kill prostate cancer cells. In the past, poor precision with application of the treatment resulted in damage to surrounding tissues and some long-term bladder complications. New techniques now allow smaller probes and more accurate monitoring of the temperature. These advances have made cryotherapy more effective with few complications. However, additional research is necessary to determine the success of cryotherapy for prostate cancer treatment.
ChemotherapyUse of powerful drugs to destroy cancer cells. Chemotherapy is a less common treatment for prostate cancer than for most other types of cancer. It is sometimes used for late-stage metastatic prostate cancer that has not responded to or no longer responds to hormone therapy.
Premarin (Conjugated Estrogens), Eulexin (Flutamide), Casodex (Bicalutamide)
Prognosis depends primarily on the stage, size, and grade of the tumor. Earlier stage and smaller tumor size have the better prognosis. Cancer that is localized to the prostate can often be eradicated completely. More advanced cancers usually cannot; most of these tumors eventually recur locally. In addition, undetected lymph node and distant metastases are more likely with more advanced tumors than with earlier stage, small tumors.
The lower the grade of the tumor, the better the prognosis. Low-grade tumors usually progress very slowly. High-grade tumors tend to behave more aggressively, growing rapidly and spreading (metastasizing) early. Metastatic disease to lymph nodes and/or distant sites has a poor prognosis. Hormonal treatment usually relieves symptoms, but relapse commonly occurs within several years. After relapse, survival is limited. Choice of treatment, if choices are available, has some influence on prognosis. For localized cancer, ten-year recurrence rates are somewhat lower after radical prostatectomy than after conventional external beam radiation. Prognosis may also be influenced by other factors. For example, there is evidence that prognosis is worse in individuals who smoke, who have a high fat diet, or who are black.
Prostate cancer must be differentiated from other causes of prostatic enlargement and/or elevated PSA. These include benign prostatic hypertrophy, chronic prostatitis, and prostatic abscess.
Urologist, medical oncologist, and radiation oncologist.
Last updated 5 July 2015