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Abstract:

In Flanders, invasive bladder cancer is the seventh most common cause of cancer for both sexes combined. Worldwide bladder cancer ranks ninth in cancer incidence. In men, it is the fifth most common malignancy. It affects merely older patients, the mean age of diagnosis is 72 years and the men/women ratio is 5.46. The relative 5 year survival, an approximation for the disease-specific survival, is 47% in men and 54% in women[i],[ii]. Both genetic and environmental factors and their interaction influence bladder cancer risk[iii] and probably also its prognosis. A review of case-control studies (2006) made at our department showed a lower selenium concentration in the blood and toenails of bladder cancer patients compared to controls. The majority of the epidemiological studies conducted on selenium and bladder cancer have indicated an inverse association between selenium and the disease[iv]. The selenium concentrations showed a dose-response with higher grades of bladder cancer. This suggests that selenium is suitable for treatment as well as chemoprevention. There have been several trials with selenium as the sole intervention or in combination with other agents to assess the effect on other cancer endpoints. These studies have reported statistically significant protective effects of selenium on all cause mortality[v], total cancer mortality and incidence[vi] and liver cancer mortality[vii]. Large clinical trials on selenium have been undertaken and are currently underway for cancers at other body sites, particularly prostate cancer (SELECT). A randomized clinical trial that will specifically investigate the effect of selenium on bladder cancer recurrence and prognosis (the SELENIB trial) has recently started in the UK. [i] E. Van Eycken, N. De Wever, Cancer Incidence and Survival in Flanders, 2000-2001. Flemisch Cancer Registry Network, VLK, Brussels, 2006. [ii] Lousbergh D, Cloes E, Op De Beeck L, Ten years of cancer in the Belgian province of Limburg: 1996-2005. Hasselt, LIKAS: 2007. [iii] Kellen E. A Belgian case-control study on bladder cancer. PhD thesis KU Leuven 2007 [iv] Brinkman M, Buntinx F, Muls E, Zeegers MP. Use of selenium in chemoprevention of bladder cancer. Lancet Oncol. 2006 Sep;7(9):766-74. [v] Blot WJ, et al. Nutrition intervention trials in Linxian, China: supplementation with specific vitamin/mineral combinations, cancer incidence, and disease-specific mortality in the general population. J NatI.Cancer Inst. 1993;85:1483-92. [vi] Dark LC, et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group. JAMA 1996:276:1957-63. [vii] Yu S i, et al.. Protective role of selenium against hepatitis B virus and primary liver cancer in Qidong. Biol Trace Elem.Res 1997:56:117-24.