From The Prostate Cancer InfoLink
The Causes of Prostate Cancer
Last Revised May 6, 1997.
Introduction | The
importance of genetics | The
significance of race | The age
factor | What about diet and
the environment? | Is prostate
cancer related to vasectomy? | Are
all cases of prostate cancer equal in risk?
Put in the simplest way, no one knows what causes some men to get prostate cancer while other men don't. Scientists and clinical researchers are working very hard to try to discover the answer to this very basic question. We hope they will find the answer soon. In the meantime, here are most of the things we do know.
The recognized risk factors for prostate cancer (i.e., things that make it more likely that a particular man may get this disease) include age, race or genetics, and environment. Approximately 334,500 American men are expected to be diagnosed with prostate cancer in 1997. This is compared to 165,000 in 1993. In other words, the incidence of prostate cancer has been rising.
Also in 1997, the number of American men who are predicted to die of prostate cancer was reported to be 41,800. Approximately 3% of all deaths of American men are currently believed to be caused by prostate cancer. This is a large number of people, but it means that only three men in 100 will actually die of the disease.
The fact that more American men have been found to have prostate cancer every year for several years now is not necessarily just because more men are getting prostate cancer. It is in fact much more likely that we have become better at finding prostate cancer. However, men are also living longer than they used to, so their chances of living long enough to get prostate cancer are increased.
If your brother or your father or your uncle has or had prostate cancer, then there is an increased chance that you will have prostate cancer. In other words, for many men the risk of prostate cancer is associated with a family history of the disease. However, this DOES NOT mean that just because your father had prostate cancer you will get prostate cancer! It DOES mean that the more relatives you have who had or have prostate cancer, the greater is your risk. This is important and affects when a man should start to have regular check-ups for signs of prostate cancer.
As with other diseases, scientists and other researchers are racing each other to find genes which are common to individuals with prostate cancer. In a variety of cancers (breast cancer, renal cell carcinoma, and others) genes have now been found which are specifically related to these cancers in some families with a very high incidence of that particular disease. We may well discover a similar situation in prostate cancer very soon. However, these genes are just one step on the way to greater knowledge. Their discovery and isolation will not immediately lead to genetic tests for prostate cancer in most individuals, let alone to some form of universal cure for this disease.
You are likely to hear more and more about the genetics of prostate cancer in years to come, along with references to genes like p53, Her-2, neu, and others, most of which will have minimal actual impact on your personal situation.
The significance of race
Prostate cancer is much more common in some races than in others. For example, Japanese men living in Japan have an extremely low incidence of prostate cancer. By comparison African American men are at very high risk of this disease. Why is this? We don't know. What we do know is that it isn't just about their genetics and heritage, because men of Japanese origin living in America have a similar risk of prostate cancer as any other average American man living in the same area! However, race can be an important factor in determining when a man should begin to have regular check-ups for signs of prostate cancer.
The age factor
As you grow older, your chance of having a diagnosis of prostate cancer increases. In fact, we believe that one of the reasons that prostate cancer is now so much more common than it was 50 years ago is very obvious: more men live longer today than they did 50 years ago. If you live longer, your chance of having a diagnosis of prostate cancer goes up proportionally.
The average age of men diagnosed with prostate cancer in America is well over 60 years. However, the range of ages is very wide. Cases of prostate cancer have first been seen in men in their twenties and in men in their nineties.
What about diet and the environment?
There is a great deal of circumstantial evidence that appears to support the idea that diet is important in the avoidance of prostate cancer. On the other hand, despite a great deal of effort to prove connections between diet and prostate cancer, we have totally failed to do this. One relatively recent major study has clearly linked prostate cancer risk with saturated fat intake. The most likely situation is that a good, well balanced diet which is high in fruit and vegetables and relatively low in red meat and fats will be better for you than a diet that is high in red meat and fats. This is true generally, and has nothing especially to do with prostate cancer! Eating well is good for you! There is no known diet that will prevent prostate cancer -- and there probably never will be!
Roughly the same is true of the environment. The cleaner your environment the less likely you are to be at risk of prostate cancer. But then that is true for nearly all cancers, and explains why smoking is such a particularly foolish thing to do if you want to avoid cancer. Smoking introduces pollutants directly into your lungs, and from there to almost every other organ of the body. You might as well go and stand beside the nearest major freeway and inhale car and truck exhaust fumes all day! Once again, however, there is no perfectly clean environment that will allow you to live without the risk of prostate cancer!
Having said that, why is it that when Oriental males move from Asia to America their risk of prostate cancer rises so rapidly? Is it the change in diet? Is it the change in the environment? Is it just that they are more likely to get tested for prostate cancer in America than they were in Asia? What is going on? Unfortunately, we don't know. We do know that there is a lower incidence of prostate cancer in the Mormon community than in the USA as a whole. Mormon diets tend to be higher in fruits and vegetables than those of the average American. Is this the defining factor? Again, we don't know.
One question that crops up over and over again is whether having
a vasectomy (the procedure that stops a man from making a woman pregnant)
can lead to a later diagnosis of prostate cancer.
First of all, it has to be said that men who have vasectomies do
appear to be more likely to have a diagnosis of prostate cancer 20
years than men who do not have vasectomies. However, it also has to
be said that there is absolutely no evidence whatsoever of a cause
and effect relationship. Indeed, there is good reason to believe that
this is a statistical coincidence that has to do with the attitudes
to health of men most likely to have vasectomies.
Basically, men who have vasectomies exhibit what is widely described
as "health-seeking" behavior. In other words, they are the
type of men who look after their health, tend to go for regular check-ups,
and generally have a lifestyle which could be considered as "healthy."
They are presumed to be more likely to have vasectomies because they
have considered that the risks associated with a vasectomy are far
lower than the risks associated with their wife/partner having a late
or unwanted pregnancy.
Now it is also reasonable to suppose that men who exhibit health-seeking
behavior are more likely to seek regular prostate examinations as
part of that behavior. This immediately implies that the same men
who seek vasectomies are more likely to have a prostate examination
than the men who do not have vasectomies. Therefore these men are
more likely to be diagnosed with prostate cancer!
The bottom line is that men who have vasectomies are somewhere between
1.5 and 2.0 times more likley to have a later diagnosis of prostate
cancer than men who have not had a vasectomy ... but that we have
no reason to believe that there is any connection between the two.