No abstract

Prostate cancer is the second most common cancer in men worldwide. Despite the global importance of this cancer, until recently little was known about risk factors apart from the well-established factors: age, family history and country of birth. The large worldwide variation in prostate cancer risk and increased risk in migrants moving from low to high risk countries provides strong support for modifiable environmental factors. We have based our review on the findings of a systematic review undertaken by an expert panel on behalf of the World Cancer Research Fund and the American Institute for Cancer Research, and new data since then, linking identified foods and nutrients with prostate cancer. Evidence indicates that foods containing lycopene, as well as selenium and foods containing it, probably protect against prostate cancer, and excess consumption of foods or supplements containing calcium are a probable cause of this cancer. The expert panel also concluded that it is unlikely that beta-carotene (whether from foods or supplements) has a substantial effect on the risk of this cancer. A recent review on environmental factors in human prostate cancer also found that there were protective effects of vitamin E, pulses, soy foods and high plasma 1,25-dihydroxyvitamin D levels. The Mediterranean diet is abundant in foods that may protect against prostate cancer and is associated with longevity and reduced cardiovascular and cancer mortality. Compared with many Western countries Greece has lower prostate cancer mortality and Greek migrant men in Australia have retained their low risk for prostate cancer. Consumption of a traditional Mediterranean diet, rich in bioactive nutrients, may confer protection to Greek migrant men, and this dietary pattern offers a palatable alternative for prevention of this disease.

In a randomized, crossover dietary intervention study, 12 Australians (of white descent) consumed a diet typical of low-income communities in China and an average Australian diet so that effects on fecal markers thought to be relevant to colon cancer risk could be compared. The Chinese diet contained 35.3 g starch/MJ daily [including 2 g resistant starch (RS)/MJ and 1.5 g nonstarch polysaccharides (NSPs)/MJ]; the Australian diet contained 12 g starch/MJ daily (including 0.8 g RS and 2.7 g NSPs/MJ). Subjects followed each diet for 3 wk. Serum cholesterol concentrations were significantly lower after the low-fat, high-starch Chinese diet than after the Australian diet (mean +/- SEM: 4.17 +/- 0.30 compared with 5.04 +/- 0.28 mmol/L, respectively, P < 0.05), a difference indicative of dietary compliance. Fecal pH was lower after the Chinese diet (6.51 +/- 0.04) than after the Australian diet (6.63 +/- 0.05; P < 0.05). For all other fecal markers examined, however, the Chinese diet produced less favorable changes, including lower fecal bulk (86 +/- 11 compared with 141 +/- 20 g wet wt/d, P < 0.01), slower transit through the gut (69 +/- 6 compared with 56 +/- 7 h, P = 0.06), lower fecal concentrations of short-chain fatty acids [72.8 +/- 7.3 compared with 98 +/- 7.6 mmol/L (including butyrate: 12.2 +/- 1.3 compared with 18.4 +/- 2.3 mmol/L), P < 0.05], and higher fecal concentrations of potentially damaging ammonia (540 +/- 50 compared with 450 +/- 40 mg/L, P < 0.01) and phenols (109.2 +/- 13.2 compared with 68.5 +/- 12.9 mg/L, P < 0.01). These results suggest that consumption of a high-starch diet alone is insufficient to reduce the risk of developing colon cancer.

From 2004–2009 a total of 226 out of a target of 750 prostate cancer patients have been randomised into the Timing of Androgen Deprivation trial between immediate and delayed androgen deprivation. A screening log was kept by participating centres for the first 928 patients, which documented the reasons for non-entry into the trial; 42.7% of screened patients were ineligible and a further 33.0% were not entered for other reasons. Fewer than 10% of patients cited not wanting to be part of a clinical trial as a reason for non-entry. Strategies to improve recruitment included broadening the eligibility criteria, encouraging international collaboration, the use and support of research nurses in the private health care environment, and the use of phone follow-up. Recruitment will be completed at the number originally intended to inform the interim analysis designed to test the validity of the statistical assumptions, and a combined survival analysis with the Canadian study is planned.