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الأحد، 19 سبتمبر، 2010

Prostate Cancer

September 18, 2010
What is the prostate gland?
The prostate gland is an organ that is located at the base or outlet (neck) of the urinary bladder. (See the diagram that follows.) The gland surrounds the first part of the urethra. The urethra is the passage through which urine drains from the bladder to exit from the penis. One function of the prostate gland is to help control urination by pressing directly against the part of the urethra that it surrounds. The main function of the prostate gland is to produce some of the substances that are found in normal semen, such as minerals and sugar. Semen is the fluid that transports the sperm to assist with reproduction. A man can manage quite well, however, without his prostate gland. (See the section on surgical treatment for prostate cancer.)
In a young man, the normal prostate gland is the size of a walnut (<30g). During normal aging, however, the gland usually grows larger. This hormone-related enlargement with aging is called benign prostatic hyperplasia (BPH), but this condition is not associated with prostate cancer. Both BPH and prostate cancer, however, can cause similar problems in older men. For example, an enlarged prostate gland can squeeze or impinge on the outlet of the bladder or the urethra, leading to difficulty with urination. The resulting symptoms commonly include slowing of the urinary stream and urinating more frequently, particularly at night. Patients should seek medical advice from their urologist or primary-care physician if these symptoms are present.
Picture of the prostate gland
What is prostate cancer?
Prostate cancer is a malignant (cancerous) tumor (growth) that consists of cells from the prostate gland. Generally, the tumor usually grows slowly and remains confined to the gland for many years. During this time, the tumor produces little or no symptoms or outward signs (abnormalities on physical examination). However, all prostate cancers do not behave similarly. Some aggressive types of prostate cancer grow and spread more rapidly than others and can cause a significant shortening of life expectancy in men affected by them. A measure of prostate cancer aggressiveness is the Gleason score (discussed in more detail later in this article), which is calculated by a trained pathologist observing prostate biopsy specimens under the microscope.
As the cancer advances, however, it can spread beyond the prostate into the surrounding tissues (local spread). Moreover, the cancer also can metastasize (spread even farther) throughout other areas of the body, such as the bones, lungs, and liver. Symptoms and signs, therefore, are more often associated with advanced prostate cancer.

Why is prostate cancer important?
Prostate cancer is the most common malignancy in American men and the second leading cause of deaths from cancer, after lung cancer. According to the American Cancer Society's most recent estimates, 192,280 new cases of prostate cancer would be diagnosed in 2009 and 27,360 would die from the disease.
The estimated lifetime risk of being diagnosed with the disease is 17.6% for Caucasians and 20.6% for African Americans. The lifetime risk of death from prostate cancer similarly is 2.8% and 4.7% respectively. As reflected in these numbers, prostate cancer is likely to impact the lives of a significant proportion of men that are alive today.
Over the years, however, the death rate from this disease has shown a steady decline, and currently, more than 2 million men in the U.S. are still alive after being diagnosed with prostate cancer at some point in their lives.
Although it is subject to some controversy, many experts in this field, therefore, recommend that beginning at age 40, all men should undergo screening for prostate cancer.
What are prostate cancer symptoms and signs?
In the early stages, prostate cancer often causes no symptoms for many years. As a matter of fact, these cancers frequently are first detected by an abnormality on a blood test (the PSA, discussed below) or as a hard nodule (lump) in the prostate gland. Occasionally, the doctor may first feel a hard nodule during a routine digital (done with the finger) rectal examination. The prostate gland is located immediately in front of the rectum.
Rarely, in more advanced cases, the cancer may enlarge and press on the urethra. As a result, the flow of urine diminishes and urination becomes more difficult. Patients may also experience burning with urination or blood in the urine. As the tumor continues to grow, it can completely block the flow of urine, resulting in a painfully obstructed and enlarged urinary bladder. These symptoms by themselves, however, do not confirm the presence of prostate cancer. Most of these symptoms can occur in men with non-cancerous (benign) enlargement of the prostate (the most common form of prostate enlargement). However, the occurrence of these symptoms should prompt an evaluation by the doctor to rule out cancer and provide appropriate treatment.
Furthermore, in the later stages, prostate cancer can spread locally into the surrounding tissue or the nearby lymph nodes, called the pelvic nodes. The cancer then can spread even farther (metastasize) to other areas of the body. Symptoms of metastatic disease include fatigue, malaise, and weight loss. The doctor during a rectal examination can sometimes detect local spread into the surrounding tissues. That is, the physician can feel a hard, fixed (not moveable) tumor extending from and beyond the gland. Prostate cancer usually metastasizes first to the lower spine or the pelvic bones (the bones connecting the lower spine to the hips), thereby causing back or pelvic pain. The cancer can then spread to the liver and lungs. Metastases (areas to which the cancer has spread) to the liver can cause pain in the abdomen and jaundice (yellow color of the skin) in rare instances. Metastases to the lungs can cause chest pain and coughing.
What are the treatment options for prostate cancer?
Deciding on treatment can be difficult, partly because the options for treatment today are far better than they were 10 years ago but also because not enough reliable data are available on which to base the decisions. Accordingly, scientifically controlled, long-term studies are still needed to compare the benefits and risks of the various treatments.
To decide on treatment for an individual patient, doctors categorize prostate cancers as organ-confined (localized to the gland), locally advanced (a large prostate tumor or one that has spread only locally), or metastatic (spread distantly or widely). The treatment options for organ-confined prostate cancer or locally advanced prostate cancer usually include surgery, radiation therapy, hormonal therapy, cryotherapy, combinations of some of these treatments, and watchful waiting. A cure for metastatic prostate cancer is, unfortunately, unattainable at the present time. The treatments for metastatic prostate cancer, which include hormonal therapy and chemotherapy, therefore, are considered palliative. By definition, the aims of palliative treatments are, at best, to slow the growth of the tumor and relieve the symptoms of the patient.

What about prostate cancer surgery?
The surgical treatment for prostate cancer is commonly referred to as a radical prostatectomy, which is the removal of the entire prostate gland. The entire prostate, seminal vesicles, and ampulla of the vas deferens are removed, and the bladder is connected to the membranous urethra to allow free urination.
The radical prostatectomy is the most common treatment for organ confined or localized prostate cancer in the United States. This operation is currently performed in about 36% of patients with organ-confined (localized) prostate cancer. The American Cancer Society estimates a 90% cure rate nationwide when the disease is confined to the prostate and the entire gland is removed. The potential complications of a radical prostatectomy include the risks of anesthesia, local bleeding, impotence (loss of sexual function) in 30%-70% of patients, and incontinence (loss of control of urination) in 3%-10% of patients.
Great strides have been made in lowering the frequency of the complications of radical prostatectomy. These advances have been accomplished largely through improved anesthesia and surgical techniques. The improved surgical techniques, in turn, stem from a better understanding of the key anatomy and physiology of sexual potency and urinary continence. Specifically, the recent introduction of nerve-sparing techniques for the prostatectomy has helped to reduce the frequency of impotence and incontinence. Of men who undergo these newer techniques, 98% are continent, and 60% are able to have an erection.
Radical prostatectomy can be performed by open surgery, laparoscopic surgery, or by robotic surgery (robotic assisted radical prostatectomy). Currently, almost 70% of radical prostatectomy surgeries in the U.S. are performed using the of the Da Vinci robotic system. For robot-assisted surgery, five small incisions are made in the abdomen through which the surgeon inserts tube-like instruments, including a small camera. This creates a magnified three-dimensional view of the surgical area. The instruments are attached to a mechanical device, and the surgeon sits at a console and guides the instruments through a viewing device to perform the surgery. The instrument tips can be moved in a variety of ways under the control of the surgeon to achieve greater precision in surgery. So far, studies show that traditional open prostatectomy and robotic prostatectomy have had similar outcomes related to cancer-free survival rates, urinary continence, and sexual function. However, in terms of blood loss during surgery and pain and recovery after the procedure, robotic surgery has been shown to have a significant advantage.
If post-treatment impotence does occur, it can be treated by sildenafil (Viagra) tablets, injections of such medications as alprostadil (Caverject) into the penis, various devices to pump up or stiffen the penis, or a penile prosthesis (an artificial penis). Incontinence after treatment often improves with time, special exercises, and medications to improve the control of urination. Occasionally, however, incontinence requires implanting an artificial sphincter around the urethra. The artificial sphincter is made up of muscle or other material and is designed to control the flow of urine through the urethra.
Transurethral resection of the prostate (TURP) involves the removal of a part of the prostate by an instrument inserted through the urethra. It is used as an alternative to prostatectomy in patients with extensive disease or those who are not fit enough to undergo radical prostatectomy to remove tissue that is blocking urine flow. This is often referred to as a channel TURP.

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