Chemoprevention

Chemoprevention is the use of a pharmaceutical or other substance (foodstuffs, food products, supplements and drugs) to prevent the development of cancer.

Prostate cancer and use of nonsteroidal anti-inflammatory drugs: systematic review and meta-analysis.

British Journal of Cancer 90(1): 93-99, January 12 2004
S Mahmud, E Franco and A Aprikian

Study purpose: Animal and laboratory studies suggest that regularly using a nonsteroidal anti-inflammatory drug like aspirin may help cut prostate cancer risk. To further assess this link, a team from Montreal’s McGill University conducted a review and meta-analysis of studies published before 2003. A meta-analysis is a statistical method that pools results from previous studies in order to re-examine the overall evidence.

Study description: The authors used Internet medical databases to find 12 relevant published studies. Seven studies were prospective trials that followed participants into the future. Another five were retrospective or case-control studies that compare a group with a disease against a similar healthy group and then examine both groups’ medical records and lifestyles to learn what factors may be linked to the disease.

Findings: Most of the studies of aspirin use reported a link suggesting a lowered cancer risk, but only two were statistically significant. The authors’ meta-analysis comparing data from all 12 studies calculated an overall relative risk or “summary odds ratio” for the link between aspirin use and prostate cancer. The overall relative risk suggested that aspirin use did cut the risk of prostate cancer: it was a negative 0.9. Studies that measured exposure to a mixture of nonsteroidal anti-inflammatory drugs were less consistent.

Conclusions: The authors believe these results indicate that aspirin use does lower prostate cancer risk. Research is needed to confirm the extent of this effect.

Chemotherapeutic Prevention Studies of Prostate Cancer

Journal of Urology 171(2, part 2 of 2): S10-S13, February 2004
Bob Djavan, Alexandre Zlotta, Claude Schulman, Pierre Teillac, Peter Iverson, Laurent Boccon Gibod, George Bartsch

Study purpose: This review from Vienna, Austria assesses European studies on cancer “chemoprevention”— foodstuffs, food products, supplements and drugs thought to slow down or stop prostate carcinogenesis, the process by which prostate cancer develops

Study description: In some cancers, there may be one factor that is linked with starting or continuing the abnormal growth that leads to disease. Although no such factor is known to kick-start prostate cancer, chemoprevention studies have focused on the role of diet, vitamins and trace mineral elements. The authors of this review looked at studies from 1998 to 2003 in order to examine all the data together. Some studies were “prospective” (participants were followed forward in time), “randomized” (participants were randomly assigned to groups comparing treatments), and “double-blinded” (neither researchers or patients knew which of several possible therapies the patient received). Others used a “retrospective” or “case-control” approach that compares a group with a disease against a similar but healthy group, and studies their medical records and lifestyles to learn what factors may be linked with the disease. Large scale randomized studies were also looked at that evaluated enzyme 5alpha-reductase inhibitors. These are medications that slow the activity of an enzyme in the male body that is linked to prostate cancer by its increase of the body’s production of the male hormone testosterone, which feeds prostate cancer cell growth.

Findings: Vitamin E and selenium, a non-metallic trace substance similar to a mineral, may help prevent prostate cancer. Ongoing research from two studies examining two 5alpha-reductase inhibiting drugs called finasteride and dutasteride may show an ability to slow down men’s male hormone production (“androgen inhibition”) and prevent prostate cancer growth.

Conclusions: The authors of the review conclude that strong evidence is still lacking for the value of foodstuffs, food products, supplements and drugs said to have an anti-cancer effect.

Prostate cancer epidemiology

the Lancet 361: 859-864, 2003
Henrik Grönberg

Study purpose: This Swedish study is an overview of the global incidence of prostate cancer. It also reviews biological “risk modifiers” that possibly offer protection from the disease.

Study description: Internet medical databases were searched from 1960 to 2002 for relevant English-language studies.

Findings: Prostate cancer accounts for almost 10% of cancers affecting men around the world but is diagnosed in very few people under 50 years old. The mean age of patients is 72–74 years, and about 85% of patients are diagnosed after turning 65. The incidence of prostate cancer varies widely between countries and rates of the disease differ by as much as 90-fold between ethnic populations. The lowest rates are in Asia and the highest among African-Americans in the USA (137 per 100,000 annually). Some researchers suggest that prostate cancer is linked to a diet that includes a large amount of fat, meat, and dairy products. While this has now been investigated in more than 40 large-scale epidemiological studies of different populations worldwide, the results of these studies are conflicting or negative. Some dietary products linked to a higher prostate cancer risk include polyunsaturated fatty acid products and calcium. Potential protective “risk modifiers” for prostate cancer include an individual’s genetic makeup, levels of bodily insulin growth factor (high levels stimulate prostate cancer cell growth), foods made from soybeans, and the antioxidant lycopene, found in tomato products. According to ongoing studies, vitamin E and the non-metallic trace element selenium may be capable of slowing tumour growth.

Conclusions: Chemoprevention (the use of a pharmaceutical or other substance to prevent the development of cancer) has the potential to control the increasing number of prostate cancer cases worldwide. If chemoprevention delayed the onset and course of prostate cancer by two to five years, the incidence of the disease and the deaths that result would drop substantially.