Sun 15 Mar 2009
News item: Where are we going with prostate cancer?
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The diagnosis and treatment of men with prostate cancer is a very difficult area. The tools we currently have for diagnosis of prostate cancer such as measurement of PSA and digital rectal examination are fairly crude and could certainly be improved. One of the problems with prostate cancer is that it exists in several forms ranging from very slow-growing tumours to aggressive tumours that expand and metastasise and are frequently fatal. Because the slow-growing tumours are quite common, especially in older men, it is true that more men die with
prostate cancer than of
prostate cancer. This is not to minimize the problem since about 3000 Australian men die of prostate cancer each year.
However using the tools we currently have available we inevitably find and treat many men with non-threatening prostate cancer that would not have caused them any harm during their lifetimes. This is a problem because it costs the healthcare system large amounts of unnecessary expense and it causes many of these men major difficulties due to the side-effects of treatment which may include urinary incontinence, impotence and bowel symptoms.
The thorny problem that we have to solve is to not only to find the prostate cancers early enough to cure them, but also to decide which ones actually need treatment. Currently examination of prostate tissue biopsies under the microscope by a pathologist allows an estimate of both the amount of cancer present and the aggressiveness of the cancer. The correlation of this scoring with subsequent tumour behaviour is far from perfect however and much of this inaccuracy is due to the fact that biopsies only sample some of the prostate and may not give a true picture of full extent of the disease present. In addition transrectal needle biopsies of the prostate are expensive, uncomfortable and may have significant side-effects.
Researchers around the world are working on this problem looking for markers of prostate cancer that are easy to measure and that distinguish between benign prostatic hypertrophy, non-aggressive prostate cancer and prostate cancer that should be treated. This is an extremely difficult task but some progress is gradually being made.
Researchers are using new sophisticated technology to look at the presence and amounts of large numbers of chemicals secreted by prostate cancers in the urine of patients. The hope is that this will allow researchers to find particular chemicals that are specific to aggressive prostate cancers and that can be measured by simpler methods in routine laboratories. Candidate chemicals have been identified are now undergoing the long and slow process of evaluating how useful they are in identifying new patients with aggressive prostate cancer.
A second approach that is being used is to look for both normal genes and altered genes that are known to be associated with prostate cancer. This approach is also showing promise and researchers have found that DNA fragments containing these genes can be found in urine and measured. Several of these genes are also being evaluated in laboratories around the world.
Thus we can hope that sometime in the future it may be possible to find markers that are easily measured in blood or urine and that specifically identify only those prostate cancers that need to be treated and bring these markers into routine use. This goal, however, is not likely to be achieved for a number of years yet.
Source: to be added