prostate cancer overview: the nuts and bolts of prostate cancer

by Juli Aistars, RN, MS, AOCN

Prostate (not prostrate) cancer is the most frequently diagnosed cancer in men other than skin cancer. In 2009, the number of new cases was estimated at 192,280 in the United States alone (1). Although women don't have a prostate gland and are not at risk for prostate cancer, they are impacted by this disease when a father, son, husband or friend faces it.

About 1 in 6 men are diagnosed with it during their lifetime, but only 1 in 34 will die from it. Fear of death is the greatest concern, but most men who have it do not die from it.

So what is prostate cancer? Let's start with the basics, looking closely at current knowledge about the prostate gland. What is a prostate gland and where is it found in the body? What does it do? Understanding the nuts and bolts of this complex gland will help us answer the question… How does prostate cancer start and how can it spread?

What is the prostate gland and where is it?

The prostate gland is the common link between a man's urinary and reproductive tracts. Located deep in the pelvis just under the urinary bladder at the outlet, it encircles the upper part of the urethra (the tube through which urine and semen pass). Urine and semen must travel through the prostate to enter the urethra and pass out of the body.

Besides the urinary bladder, other structures found close to it are the rectum, the sphincters that control urine flow, the seminal vesicles, the vas deferens, and a network of arteries, veins and nerves. The prostate is enclosed in a capsule or membranous covering.

In a young man in his 20s, the gland is the size of a walnut or about 20 grams. It grows larger as a man ages ^(2,3,4,5). Until something goes wrong with it, a man may not even be aware of it.

The anatomy of the prostate gland has been a matter of controversy in years past. The old belief that the prostate is organized into lobes was questioned since distinct lobes are not apparent in the normal adult prostate. The prostate is not just one gland but rather a collection of many tiny glands which are connected by hundreds of tiny ducts or tubes which carry the fluid these glands produce to the urethra during ejaculation. The concept of zones is now the widely accepted method of describing different areas of the prostate ^(3,6).

The prostate has distinct zones which are described slightly differently depending on the reading source. The basic zones are the peripheral, central, transition, anterior (consists mainly of smooth muscle), and preprostatic tissue (plays a key role during ejaculation). The areas of concern when something goes wrong with the prostate are the peripheral and the transition zones. See Figure 2 below.

Figure 2: Zones of the prostate gland

     

The peripheral zone accounts for the bulk of the normal prostate (about 70% of the glandular tissue). It includes all of the tissue at the apex (bottom of the prostate) and the tissue near the back of the prostate next to the rectum. This is the area most susceptible to prostate cancer and where prostate cancer is most often found ^(5,6,7).

The transition zone surrounds the prostatic urethra that passes through the prostate. This zone is the common site where the prostate enlarges and presses on the urethra as a man grows older ⁽⁵⁾.

The prostate is supplied by large, paired groups of nerves and blood vessels that run along the outside edge on either side of the prostate. In the body, they are not separate but bundled together to form the neurovascular bundles on either side of the prostate.

The seminal vesicles are just behind the bladder and above the prostate. They are about 4 inches long and 2 inches wide.

The vas deferens is a long tube that carries sperm from the testicle (found in the scrotum) to the urethra. It merges with the seminal vesicle duct to form a canal (ejaculatory duct) which enters the prostate and opens into the urethra that is encircled by the prostate ⁽²⁾.

What does the prostate gland do?

A gland is an organ or structure that produces a substance that is used in another part of the body. The prostate makes part of the semen (the fluid that transports the sperm), which contains sugars and minerals that serve as nutrients to sperm. The prostate gland helps control urination by pressing against the part of the urethra that is surrounded by it. It may also prevent infections in the reproductive and urinary tract. Its name in Greek means "protector". The prostate's growth and function are influenced by testosterone which is a hormone. Testosterone is produced in the testicles and converted to another hormone called dihydrotestosterone (DHT) in the prostate ⁽⁵⁾.

The prostate is an expendable organ-a man can live without one. The more important question than what it does is: What goes wrong with it? The three common prostate disorders are:

• prostate cancer
• BPH (benign prostatic hyperplasia) or enlargement of the prostate gland
• prostatitis or a common cause of urinary tract infections

The only one which will be addressed here is prostate cancer.

What is prostate cancer and how can it spread?

Our bodies are made up of billions of cells. Cells are replaced in an organized manner. Cancer starts when the growth of cells becomes uncontrolled and leads to a tumor. There are benign tumors that are noncancerous. Cancerous tumors are referred to as malignant. Prostate cancer is a malignant or uncontrolled growth of the glandular cells of the prostate ⁽²⁾. It is most commonly found in the peripheral zone of the prostate.

Malignant tumors have the potential to spread and cause damage to other tissues of the body and they can potentially cause death. They can spread into surrounding tissues or travel through body fluids such as blood and lymph, spreading the cancer to other parts of the body. When cancer spreads beyond the surrounding area, it is called metastasis ⁽²⁾. Prostate cancer in particular, when it spreads, commonly involves the bones ⁽⁶⁾. Even though prostate cancer may spread to the bone, lungs or liver, it is still prostate cancer since that is where it started ⁽²⁾.

All prostate cancers are not alike. In general, they tend to be slow-growing, usually taking 2-4 years to double in size. Prostate cancer often grows significantly slower than colon or breast cancer. However, this is not always the case.

Prostate cancer is age-related and rarely diagnosed in men younger than 40. It becomes much more common in men 65 and older ⁽²⁾. Nearly all men will have prostate cancer if they live long enough, though it may never cause problems.

Prostate cancer is multifocal or found in more than one zone in about 85% of cases ⁽³⁾. There are different types of prostate cancer; specific prostate cancers can be identified by their appearance under a microscope. About 95% of them are classified as adenocarcinomas. More rare types of prostate cancer are: small cell, squamous cell, and transitional cell carcinomas ⁽⁷⁾.

Prostate cancer is a complex disease. Hopefully, breaking it down to the nuts and bolts has made it easier to understand. Knowledge is power.

This information is relevant to all men and their partners. Know your risk, know about the disease, know your options.

References

1. Cancer Facts & Figures 2009: American Cancer Society.
2. Bostwick, D.G., Crawford, E.D., Higano, C.S., Roach, M. (2005) American Cancer Society's Complete Guide to Prostate Cancer. American Cancer Society, Atlanta, GA.
3. Ellsworth, P. (2009) 100 Questions & Answers About Prostate Cancer (ed 2). Jones and Bartlett Publishers, Sudbury, MA.
4. Scardino, P.T., Kelman, J. (2006) Dr. Peter Scardino's Prostate Book. Avery, New York, NY.
5. Walsh, P.C., Worthington, J. F. (2007) Dr. Patrick Walsh's Guide to Surviving Prostate Cancer (ed 2). Wellness Central, New York, NY.
6. Ayala, G., Wheeler, T.M. (2006) Anatomy and Pathology of Prostate Cancer. In Vogelzang, N.J., Scardino, P.T., Shipley, W.U., Debruyne, F.M.J., Linehan, W.M., editors: Genitourinary Oncology (ed 3). Lippincott, Williams & Wilkins, Philadelphia, PA.
7. Zelefsky, M.J., Eastham, J.A., Sartor, O.A., Kantoff, P. (2008) Cancer of the Prostate. In DeVita V.T.,Hellman S., Rosenberg S.A., editors: Cancer: Principles & Practice of Oncology, (ed 8), volume 1, Philadelphia, 2008, Lippincott, Williams & Wilkins.

This article has been reviewed by Janet Casperson, BS, MSN, ANP-C.

Posted August 2010

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