The Big Picture | What Is It? | Diagnosis | Understanding Risk  | Treatment Options | Prostate Cancer Results Study Group

Prostate Cancer: What Is It?

Prostate cancer is the most common form of cancer in men. According to the American Cancer Society, approximately 200,000 men in the United States are diagnosed with prostate cancer every year. This number is rising largely because the baby boom generation is now reaching the age where prostate cancer is more prevalent. The exact cause of prostate cancer is unknown. An average American man has a one in six chance of being diagnosed with prostate cancer during his lifetime. The good news (according to the most recent data) for men with prostate cancer, is that the expected 5-year survival rate is nearly 100% and the 10-year survival rate is 91%. This is likely due to early detection, improved treatments and salvage hormone therapy.

Detection

As with many forms of cancer, early detection provides the greatest chance of cure. For this reason, it is important for all men over the age of 50 (age 40 if you are African-American or have a family history) discuss with their physician about regularly scheduled annual screening exams which include a Prostate Specific Antigen (PSA*) blood test and Digital Rectal Exam (DRE*).

PSA Screening

Some controversy exists regarding PSA screening. Some argue against screening, as many men with newly diagnosed prostate cancer may die of some other cause before an untreated prostate cancer would kill them. Others point out that early detection and treatment reduces the likelihood of suffering from the pain of metastatic disease (spread of cancer to bones and lymph nodes) and that the death rate from prostate cancer in the USA has dropped dramatically since PSA screening has become prevalent. For example, the five year survival in 1985 was 69% vs. almost 100% now.

A recent European study involving over 150,000 men has shown a 31% reduction in mortality in those that underwent prostate cancer screening versus those that did not.

Risk Factors

Age
Age is the strongest risk factor for prostate cancer. Prostate cancer is very rare before the age of 40, but the chance of having prostate cancer rises rapidly after age 50. Almost 2 out of 3 prostate cancers are found in men over the age of 65.

Race/Ethnicity
Prostate cancer occurs more often in African-American men than in men of other races. African-American men are also more likely to be diagnosed at an advanced stage, at an earlier age and are more than twice as likely to die of prostate cancer as white men. Prostate cancer occurs less often in Asian-American and Hispanic/Latino men than in non-Hispanic whites. The reasons for these racial and ethnic differences are not clear.

Nationality
Prostate cancer is most common in North America, northwestern Europe, Australia and on Caribbean islands. It is less common in Asia, Africa, Central America and South America. The reasons for this are not clear. More intensive screening in some developed countries likely accounts for at least part of this difference, but other factors are likely to be important as well. For example, lifestyle differences (diet, etc.) may be important. Men of Asian descent living in the United States have a lower risk of prostate cancer than white Americans, but their risk is higher than that of men of similar backgrounds living in Asia.

Family History
Prostate cancer seems to run in some families which suggests that in some cases there is an inherited or genetic factor. Having a father or brother with prostate cancer more than doubles a man’s risk of developing this disease. (The risk is higher for men with an affected brother than for those with an affected father.) The risk is much higher for men with several affected relatives, particularly if their relatives were young at the time the cancer was found.

Genes
Scientists have found several inherited genes that seem to raise prostate cancer risk, but they probably account for only a small percentage of cases overall. Genetic testing for most of these genes is not yet available. Recently, some common gene variations have been linked to the risk of prostate cancer. Studies to confirm these results are needed to see if testing for the gene variants will be useful in predicting prostate cancer risk.

Some inherited genes raise the risk for more than one type of cancer. For example, inherited mutations of the BRCA1 or BRCA2 genes are the reason that breast and ovarian cancers are much more common in some families. Mutations in these genes may also increase prostate cancer risk in some men, but they account for a very small percentage of prostate cancer cases.

Diet
The exact role of diet in prostate cancer is not clear, although several different factors have been studied.

Men who eat a lot of red meat or high-fat dairy products appear to have a slightly higher chance of getting prostate cancer. These men also tend to eat fewer fruits and vegetables. Doctors are not sure which of these factors is responsible for raising the risk.

Some studies have suggested that men who consume a lot of calcium (through food or supplements) may have a higher risk of developing advanced prostate cancer. Most studies have not found such a link with the levels of calcium found in the average diet, and it’s important to note that calcium is known to have other important health benefits.

Obesity
Most studies have not found that being obese (having a high amount of extra body fat) is linked with a higher risk of getting prostate cancer. Some studies have found that obese men have a lower risk of getting a low-grade (less dangerous) form of the disease, but a higher risk of getting more aggressive prostate cancer. The reasons for this are not clear. Studies have also found that obese men may be at greater risk for having more advanced prostate cancer and of dying from prostate cancer, but this was not seen in other studies.

Exercise
Exercise has not been shown to reduce prostate cancer risk in most studies. But, some studies have found that high levels of physical activity, particularly in older men, may lower the risk of advanced prostate cancer. More research in this area is needed.

Inflammation of the Prostate
Some studies have suggested that prostatitis (inflammation of the prostate gland) may be linked to an increased risk of prostate cancer, but other studies have not found such a link. Inflammation is often seen in samples of prostate tissue that also contain cancer. While the link between the two is not yet clear, this is an active area of research.

Infection
Researchers have also looked to see if sexually transmitted infections (like gonorrhea or chlamydia) might increase the risk of prostate cancer, possibly, by leading to inflammation of the prostate. So far, studies have not agreed and no firm conclusions have been reached.

Vasectomy
Some earlier studies had suggested that men who had a vasectomy (minor surgery to make men infertile), especially those younger than 35 at the time of the procedure, may have a slightly increased risk for prostate cancer. But, most recent studies have not found any increased risk among men who have had this operation. Fear of an increased risk of prostate cancer should not be a reason to avoid a vasectomy.

Although the exact cause of prostate cancer is unknown, research has shown that men with certain risk factors are more likely than others to develop prostate cancer. Having a risk factor doesn’t mean that you will get prostate cancer, but rather you are at greater risk of developing the disease.

Prevention
Two randomized trials have shown that those at higher risk for developing prostate cancer can reduce their risk by 25% by taking a 5-alpha reductase daily. The first study involved Finasteride, 5 mg daily. A 25% reduction in the diagnosis of prostate cancer was noted in those that were randomized to take the drug as compared to those that took placebo (a fake pill). The second study used a different 5-alpha reductatse (Avodart, 0.5mg daily). Similarily, a 25% reduction in prostate cancer was seen. These medications have not been shown to make prostate cancer regress after it has been diagnosed.

If you do not have prostate cancer, but have a family history of prostate cancer, you may wish to speak to your physician about taking Finasteride or Avodart, preventatively.

Anatomy
The prostate is located just below the bladder, in front of the rectum and beneath the pubic bone. It is a plum sized gland that is part of the male reproductive system. The urethra (the tube from the bladder to the penis that urine flows through) runs through the center of the prostate gland. Above the prostate and attached to it are the right and left seminal vesicles. The seminal vesicles produce the fluid, which, when mixed with sperm in the ejaculatory ducts within the prostate, results in semen. Diagram

Grade
Prostate cancer is a cancer of the cells in the prostate gland. The cancer is graded based on its Gleason grade (appearance) on low power microscope scaled from 1-5, with 5 being the most aggressive grade (most likely to spread outside of the prostate). Since there are often 2 grades of cancer present in the biopsy, pathologists use the sum of the Gleason grades to give an overall score. For example, if all the cells are graded a “3”, then the cancer is a Gleason grade 3 + Gleason grade 3 = Gleason Score 6. If there is grade 4 present, then it would be either a Gleason score 3+ 4 = 7, if there is more grade 3, or a Gleason score 4+3 = 7, if there are more grade 4 cells present. The grade has important implications for predicting whether the disease is beyond the gland.

Stage
Staging prostate cancer is based on the physical exam and any diagnostic studies performed. Since most patients do not require bone scans, CTs and other imaging tools, the digital rectal exam provides this staging information. If there is no palpable nodule in the gland, the Stage is T1. T1 is divided into 3 categories based on how it was diagnosed. T1a and T1b are reserved for patients in which the cancer was found after removing part of the gland to relieve blockage***. T1c refers to no palpable disease on digital rectal exam. Note that even if the pathology shows disease on both sides of the gland, this does not affect the stage.

T2a refers to a small nodule on one side. T2b means that the nodule occupies most of one lobe, and T2c means that the nodule occupies parts of both lobes. T3 is quite rare and means that the nodule extends outside the gland or seen outside the gland on an imaging study (MRI or CT).

PSA
A PSA blood test and digital rectal exam (DRE) are the two standard screening tests for prostate cancer. PSA is an enzyme produced exclusively by the prostate. PSA is produced by both normal prostate cells and prostate cancer cells. Even prostate cancer cells that spread (metastasize) to other areas of the body continue to make PSA. Small amounts of this enzyme in the bloodstream are normal, so an elevated PSA alone does not necessarily indicate cancer. Normal levels are between 0-2.5 ng/ml. Levels higher than this should be evaluated. Benign elevations of PSA can be caused by and enlarged prostate, prostate inflammation, infection or trauma. Often, the DRE does not reveal any abnormalities. Sometimes, the cancer is palpable on a DRE but the PSA is less than 2.5 ng/ml. For this reason, the PSA blood test together with the DRE is important for early detection.

The PSA is used not only for detection but for monitoring results after treatment. After surgery, it is likely to drop dramatically. After any form of radiation (Seeds, Proton beam, IMRT, etc.), the PSA often drops slowly as the cancer cells die and disappear. It can sometimes take several years for the PSA to reach its final nadir (lowest level). Remember that cells that escape the prostate area can still produce PSA. So, regular PSA testing after treatment (surgery or radiation) can detect not only local re-growth of cancer in the prostate or post-surgical prostate bed but can also detect metastatic prostate cancer (and only prostate cancer).

“What you need to know about Prostate Cancer”. National Institute of Health, 2005.
“Understanding Prostate Changes”. National Institute of Health, 2004.

* PSA (Prostatic Specific Antigen): A protein produced by both normal and cancer cells of the prostate gland. PSA is present in small quantities in the serum of normal men, and is often elevated in the presence of prostate cancer and in other benign prostate disorders. A blood test to measure PSA is considered the most effective test currently available for the early detection of prostate cancer. Rising levels of PSA over time can be indicative of either localized and metastatic prostate cancer (CaP).
** Digital Rectal Examination (DRE):  A physical exam in which the prostate is examined by inserting a gloved finger into the rectum and palpating the posterior part of the gland.
*** TUIP: Transurethral incision of the prostate; a procedure that can be done to is to relieve urinary obstruction; less traumatic to the prostate than a TURP.