Research

Professor Anthony Miller provides further comment

The prostate is a walnut-sized gland of the male reproductive system that makes part of the liquid called seminal fluid that mixes with sperm from the testicles to make semen.

Cancer of the prostate is the most common cancer in Canadian men.  According to the Canadian Cancer Society, about 25,500 men will be diagnosed with prostate cancer in 2009 and 4,400 will die from it.   The risk is highest after age 60.

No one argues with these facts.  But early detection of prostate cancer remains controversial.  At the centre of the issue is the PSA test.  Prostate-specific antigen (PSA) is a protein produced by cells of the prostate.  The PSA test, developed about 20 years ago, measures the level of PSA in the blood.  A reading over four indicates there might well be prostate cancer.

But detection doesn’t mean treatment needs to follow.  Professor Anthony Miller, associate director of research at U of T’s Dalla Lana School of Public Health was a member of a major U.S.-based research study that found that having the test done doesn’t reduce death from the disease and detection by way of PSA often results in men being treated for cancers that were so slow-growing that they didn’t require treatment.  And for those men who do receive treatment (such as surgery and radiation therapy) but do not require it, the complications from treatment outweigh benefits.  Complications can include incontinence (inability to control urine flow) and erectile dysfunction.

We asked Professor Miller to provide further comment.

What lead you to do this research study in the first place?

For some 20 years or more, there were discussions ongoing in the US National Cancer Institute as to whether there should be a trial on not only prostate cancer but a new trial in relation to lung cancer and a new evaluation of colon cancer screening.  It was eventually decided to put all this together.  So I found myself part of the original group and spent a year in the US working on this trial.

We had decided that, given that people were advocating the PSA test without evidence of benefit, and given our concern in terms of the complications, we thought it was absolutely essential that there should be a trial.

We seem to be hearing more about prostate issues in men, especially prostate cancer. Is it because prostate cancer is primarily a disease of older men and we are seeing it more now because men are living longer?

Yes, partly, but the other major reason is the advocacy of PSA testing.  What is very clear is that as a result of PSA testing an additional number of prostate cancers have been diagnosed in men starting from the age of 50, but particularly in men in their 60s or 70s that otherwise would never have come to light in that particular individual’s lifetime.  We call this ‘overdiagnosis.’

When you are able to dig deeper into the natural history of a cancer, you can find a number of things which are really not yet cancers that you don’t need to do anything about.  Doctors tend to follow what they regard as best practice in the interest of the patient and that means people get treated, with large numbers of radical prostatectomies being done for cancers which did not need to be detected and were not destined to kill that person.

And yet the people who’ve had these cancers diagnosed, even though they have complications from the surgery, are convinced having gone through all of this that their lives have been saved, so they become advocates, and the whole thing accelerates.

Before the PSA test was developed, how was prostate cancer diagnosed?  And what are the symptoms?

The symptoms of prostate cancer are almost indistinguishable from the symptoms of what we call a ‘benign enlargement of the prostate,’ which tends to occur in older men and can cause difficulty in urination and can even cause retention of urine.

Basically the determination that someone has a prostate cancer as distinct from a benign abnormality can only be done by doing biopsies.  In the past, if someone developed those symptoms and the GP or urologist did a digital rectal examination, if there were no clinical signs of cancer then they would just treat the prostate enlargement and very often they would do a simple operation called a ‘trans urethral section,’ where you put a catheter into the prostate and, using a small knife, get rid of the obstruction. As that became more popular, a number of what we call ‘latent prostate cancers’ were diagnosed but the actual increase in the detection only came about when the PSA test came in.

What lifestyle choices promote a healthy prostate?

Some studies have found suggestions for protective effect of some substances, such as tomatoes and products that use tomatoes as a primary ingredient, like ketchup and tomato sauce.  Some studies suggest that obese men are more likely to have prostate cancer and some have suggested that maybe high fat in the diet is more likely to increase the risk.  There is not much evidence of protective effects from fruits and vegetables other than the tomato research, and none of this is definitive.  Overall, the research points to a possible benefit, as it does for many other cancers, for just being careful about our diet.

Should men have the PSA?

Yes, but only have it if after consulting with your doctor you are still worried about your prostate, but remember there is increasing evidence there is no need to do it every year.  One of the interesting things about the current controversy is that most of the subjects in the European trial did not have PSA testing every year, but every four years, and in the US trial there is evidence that if you have a normal PSA, it is very unlikely you will have problems with your prostate in terms of cancer for the next five or six years.

• Read the study

Tags: Anthony Miller, Behind the Headlines, cancer, Health, public health