- what is prostate cancer?
- what causes prostate cancer?
- how is prostate cancer found?
- what's new in prostate cancer research?
the prostate is a gland found only in men. the prostate is just below the bladder and in front of the rectum. it is about the size of a walnut. the tube that carries urine (the urethra) runs through the prostate. the prostate contains cells that make some of the fluid (semen) that protects and nourishes the sperm.
the prostate begins to develop before birth and keeps on growing until a man reaches adulthood. male hormones (called androgens) cause this growth. if male hormone levels are low, the prostate gland will not grow to full size. in older men, though, the part of the prostate around the urethra may keep on growing. this causes bph (benign prostatic hyperplasia) which can result in problems with urinating. but bph is not cancer.
although there are several cell types in the prostate, nearly all prostate cancers start in the gland cells. this kind of cancer is known as adenocarcinoma.
most of the time, prostate cancer grows slowly. autopsy studies show that many older men (and even younger men) who died of other diseases also had prostate cancer that never caused a problem during their lives. these studies showed that 7 or 8 out of 10 men had prostate cancer by age 80. but neither they nor their doctors even knew they had it.
we do not yet know exactly what causes prostate cancer, but we do know that certain risk factors are linked to the disease. a risk factor is anything that increases a person's chance of getting a disease. different cancers have different risk factors. some risk factors, such as smoking, can be controlled. others, like a person's age or family history, can't be changed. but having a risk factor, or even several, doesn’t mean that you will get the disease. many people with one or more risk factors never get cancer, while others with this disease may have had no known risk factors.
risk factors for prostate cancer
age is the strongest risk factor for prostate cancer. the chance of getting prostate cancer goes up quickly after a man reaches age 50. about 2 out of every 3 prostate cancers are found in men over the age of 65.
for unknown reasons, prostate cancer is more common among african-american men than among men of other races. african-american men are also more likely to have a more advanced disease when it is found and are more likely to die of the disease. 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.
prostate cancer is most common in north america, northwestern europe, and a few other places. it is less common in asia, africa, central and south america. the reasons for this are not clear. more testing in some developed countries likely accounts for at least part of this difference, but other factors are likely to be important as well.
prostate cancer seems to run in some families. men with close family members (father or brother) who have had prostate cancer are more likely to get it themselves, especially if their relatives were young when they got the disease.
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 seem to have a greater chance of getting prostate cancer. these men also tend to eat fewer fruits and vegetables. doctors are not sure which of these factors causes the risk to go up.
prostate cancer can often be found early by testing the amount of psa (prostate-specific antigen) in your blood. another way prostate cancer is found early is when the doctor does a digital rectal exam (dre). because the prostate gland lies just in front of the rectum, during the exam the doctor can feel if there are any bumps or hard places on the prostate. these might be cancer. if you have had routine yearly exams and either one of these test results becomes abnormal, any cancer you might have has probably been found at an early, more treatable stage.
since about 1990 it has become more common for men to have tests to find prostate cancer early. the prostate cancer death rate has dropped, too. but we do not yet know if this drop is the direct result of the tests. these tests are not perfect, though. wrong test results could lead to excess worry, or even an unneeded biopsy or other tests.
until more is known, you should talk to your doctor about whether or not you want to be tested. things to take into account are your age and your health. if you are young and you get prostate cancer, it will probably shorten your life if it is not caught early. but if you are older or in poor health, then prostate cancer may never become a major problem because it often grows so slowly.
psa blood test
psa (prostate-specific antigen) is a substance made by the prostate gland. although psa is mostly found in semen, a small amount is also found in the blood. most men have levels under 4 ng/ml (nanograms per milliliter) of blood. prostate cancer can cause the level to go up. if your level is between 4 and 10, you have about a 1 in 4 chance of having prostate cancer. if it is above 10, your chance is over 50% and goes up as the psa level goes up. but some men with a psa below 4 can also have prostate cancer.
factors other than cancer can also cause the psa level to go up, including:
- having bph
- an infection or inflammation in the prostate (prostatitis)
- taking certain drugs can change levels (be sure your doctor knows all medicines, vitamins, herbs, and supplements you are taking.)
- getting older
if your psa level is high, your doctor may advise a prostate biopsy to find out if you have cancer.
there are a number of new types of psa tests that might help to show whether or not a man needs more testing. not all doctors agree on how to use these new psa tests. you should talk to your doctor about your cancer risk and any tests that you are having.
there is no question that the psa test can help spot prostate cancer. but it can’t tell how dangerous the cancer is. the problem is that some prostate cancers are slow-growing and may never cause problems. but because of a high psa level, many men will be found to have prostate cancer that would never have led to their deaths. often these men are being treated with either surgery or radiation because they are uncomfortable not having treatment. doctors and patients are still struggling to decide who should receive treatment and who can be followed without treatment.
dre (digital rectal exam)
to do the dre the doctor inserts a gloved, lubricated finger into the rectum to feel for any irregular or firm areas that might be cancer. the prostate gland is next to the rectum, and most cancers begin in the part of the gland that can be reached by a rectal exam. while it is uncomfortable, the exam isn’t painful and takes only a short time.
the dre is less effective than the psa blood test in finding prostate cancer, but it can sometimes find cancers in men with normal psa levels. for this reason, acs guidelines recommend that when prostate cancer screening is done, both the dre and the psa should be used. the dre is also used once a man is known to have prostate cancer. it can help tell whether the cancer has spread beyond his prostate gland. it can also be used to find cancer that has come back after treatment.
researchers are now studying newer forms of treatment for early stage prostate cancer, either as the first treatment or as treatment after unsuccessful radiation treatment.
one promising treatment, known as high-intensity focused ultrasound (hifu), destroys cancer cells by heating them with highly focused ultrasonic beams. while it has been used more in europe, it is not commonly used in the united states at this time. studies are now going on to find out if it is safe and effective.
nutrition and lifestyle changes
a recent study found that in men with a rising psa after surgery or radiation therapy, drinking pomegranate juice seemed to slow the time it took the psa level to double. larger studies are now being done to try to confirm these results.
some encouraging early results have also been reported with flaxseed supplements which seemed to slow the rate at which prostate cancer cells multiplied. more research is needed to confirm this finding.
a recent report found that men who chose not to have treatment for their localized prostate cancer may be able to slow its growth with major lifestyle changes. the men ate a vegan (no meat, fish, eggs, or dairy products) diet and exercised a lot. they also went to support groups and yoga. after 1 year the men saw a slight drop in their psa level. it isn't known whether this effect will last since the report only followed the men for 1 year. also, some men may find these changes hard to follow.
researchers continue to look for foods that affect prostate cancer risk. scientists have found some substances in tomatoes and soybeans that may help to prevent prostate cancer. they are trying to develop related compounds that are even more powerful and might be taken as supplements. so far, most research suggests that a balanced diet that includes these foods as well as other fruits and vegetables is a better approach than taking these substances as supplements.
some studies suggest that certain vitamins and minerals could lower prostate cancer risk, and larger studies of this issue are still in progress. certain medicines already in use for other prostate problems may also lower a man’s risk of getting cancer.
new research on genes linked to prostate cancer helps scientists better understand how prostate cancer grows. tests to find abnormal prostate cancer genes could also help tell which men are at high risk. they could then be tested more often. further research could provide answers about the chemical changes that lead to prostate cancer. then, perhaps, we could design drugs to reverse those changes.
one of the biggest problems now facing doctors and their patients with prostate cancer is figuring out which cancers are more likely to spread. knowing this could help decide which men need treatment and which could be better served by watchful waiting. researchers are now trying to find genetic clues about which cancers are more likely to grow fast and spread.
these are special types of proteins that are made in the lab. they target certain parts of the prostate cancer cells. several different ones are being developed and tested.