UPDATE - Issue 20 - Winter 2004
Can Prostate Cancer be Prevented?
- Professor Roger Kirby
Prostate cancer is now the most commonly detected malignancy in men. Over 27,000 new cases are diagnosed every year in the UK. Men especially at risk include those with a strong family history of the disease, especially when the affected relatives are younger than 60 years of age. For these high risk individuals, and indeed for the rest of us males, an effective strategy to prevent prostate cancer would be highly beneficial.
Selenium evidence
But what is the hard evidence that prostate cancer can be prevented? The natural product selenium was shown in one large study to reduce the incidence of prostate cancer by 48% when matched against placebo. A follow-up study showed a greater than 69% reduction in prostate cancer incidence in those with high compared with low selenium levels in the blood. Selenium occurs naturally in foods such as Brazil nuts and can be purchased in health food shops either alone or in combination with Vitamins A, C and E (Selenium ACE). The only significant side-effect is gastro-intestinal disturbance.
Vitamin E
Another natural preventative product is vitamin E. A large Finnish study of male smokers revealed that vitamin E reduced prostate cancer mortality by 41%. On the basis of this I have been in the habit of advising patients to take Vitamin E supplements, usually in combination with selenium. However, a recent paper by Edgar Millar in the January 2005 issue of Annals of Internal Medicine reports that an analysis of 11 trials testing high dose Vitamin E shows an increased mortality in those taking doses greater than 150 International Units per day, possibly as a result of cardiovascular problems. Accordingly it is suggested that the daily dose of Vitamin E be restricted to 150 International Units per day, a dose not associated with such problems.
Proscar™ and Avodart™
The 5 alpha-reductase inhibitor finasteride (Proscar™), which is extensively used as a treatment for Benign Prostatic Hyperplasia, has recently been rigorously tested in a very large trial for preventative properties against prostate cancer. 18,882 men were randomly assigned to take either finasteride or inactive placebo for seven years. A 24.8% reduction in prostate cancer incidence was detected in the finasteride-treated patients, but disappointingly those cancers that did occur in this group were of higher grade (i.e. more aggressive in nature) than those diagnosed in men receiving placebo. The newer prostate shrinking drug dutasteride (Avodart™), which has a similar mechanism of action, is also being tested for preventative activity, but no conclusive results are available yet. Both Proscar™ and Avodart™ improve prostatic symptoms, but carry a small risk of reducing sex drive and erections. This is reversible on stopping the tablets.
Tomatoes
A host of other complementary therapies are claimed to protect against prostate cancer. Evidence for their safety and effectiveness however is sparse. One exception is lycopene which is a carotenoid found abundantly in the skin of tomatoes. A study of dietary habits in 41 countries found a strong association between tomato consumption and reduced prostate cancer mortality. Moreover, lycopene can inhibit prostate cancer cell growth in the laboratory. Much less robust evidence is available to support the contention that soya products, green tea and St John's Wort are beneficial, and more studies are required to confirm this.
Summing up
So what steps should we take currently to avoid this very prevalent disease? A balanced diet, low in saturated fats, is recommended, with plenty of tomatoes. Selenium 200 micrograms and Vitamin E in a dose not exceeding 150 International Units per day are probably helpful. Regular exercise and careful maintenance of optimum weight helps to protect against both prostate cancer and cardiovascular disease. I try to follow this regime myself and advise my patients to do the same. Furthermore, I believe in PSA tests annually together with a cholesterol profile, because in my book, earlier detection offers a better opportunity of cure.