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Query: UMLS:C0376358 (prostate cancer)
 59,338 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This is a report of research efforts underway at the Arizona Cancer Center. These efforts build upon Larry Clark's unanticipated clinical prevention trial results: those results indicated that 200 microg/day of selenium in selenized yeast decreased prostate cancer risk by almost 60%. The trials underway address various phases of the possible preventive activity of selenium. The first of these, for men who are suspected to have prostate cancer but who have had a biopsy revealing no evidence of cancer, will test the ability of selenium to prevent the development of clinical prostate cancer. The second is for men with high-grade prostatic intraepithelial neoplasia; the trial will test whether selenium will prevent the development of prostatic cancer in this high-risk group. The third trial is for men who have been diagnosed with prostate cancer and are scheduled for prostatectomy: the trial is designed to test whether evidence of selenium-linked changes can be identified in the tissue removed at prostatectomy. The fourth trial is for men who have been diagnosed with prostate cancer but who have chosen neither surgery nor irradiation; this trial will evaluate whether treatment with selenium will inhibit the progress of prostate cancer. Together, these trials will provide important information as to the prostate cancer chemopreventive potential of selenium.
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PMID:Randomized, controlled chemoprevention trials in populations at very high risk for prostate cancer: Elevated prostate-specific antigen and high-grade prostatic intraepithelial neoplasia. 1129 23

Prostate cancer, even with its substantial public health impact of 180,400 new cases and 31,900 deaths estimated for 2000, still has a very low annual incidence (0.27% for men 34.4 years and older), which makes designing and conducting efficient prostate cancer prevention trials a challenge. Definitive prevention trials with cancer endpoints, such as the Breast Cancer Prevention Trial (BCPT), Prostate Cancer Prevention Trial (PCPT), and Selenium and Vitamin E Cancer Prevention Trial (SELECT), require long trial duration (up to 12 years) and large sample size (up to 32,400 subjects) to accomplish their objectives. This article discusses design concepts for potential prostate cancer prevention trials that require fewer years, subjects, and resources to complete. Design elements, such as high-risk populations, randomization, surrogate endpoints, including quality-of-life endpoints, masking/blinding, and various clinical/statistical designs (including 1-way layout, all-versus-none, factorial, and adaptive designs), are discussed, along with the ultimate goal of gaining US Food and Drug Administration approval for prostate-cancer preventive agents that can improve public health by reducing prostate cancer incidence and mortality.
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PMID:Design considerations for efficient prostate cancer chemoprevention trials. 1129 29

In this review, we consider the evidence from geographic and metabolic epidemiology and laboratory studies with human prostate cancer cell lines and animal models that emphasizes the need for the development and implementation of a dietary intervention trial in prostate cancer patients. It is concluded that such a trial should include a reduction in total fat consumption to 15% of total calories and supplementation of the diet with selenium, vitamin E, and a soya product. The low-fat intervention would provide an appropriate reduction in the intake of any specifically targeted dietary fatty acid, such as linoleic acid or alpha-linolenic acid.
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PMID:Nutrition and prostate cancer: a proposal for dietary intervention. 1130 6

Nutrition is apparently a major risk factor for the development and progression of prostate cancer. Based on experimental studies and epidemiologic data mainly from case-control studies or cohort studies, there is strong evidence that reduction of the total energy consumption, a diet comprising less than 30% fat, and increased intake of phytoestrogens, vitamins D and E and selenium could yield a decreased prostate cancer incidence. Furthermore, some of these measures appear to have antitumoral capacity even in the presence of the disease. These observations have provided a rationale to forward large prospective trials on dietary interventions to prove the efficacy of the concept and further delineate the correlation between nutritional compounds and prostate cancer risk. These chemoprevention trials are either aiming a reduction prostate cancer incidence or a decrease in tumor progression. Depending on the study design, large numbers of individuals need to be enrolled and long follow-up intervals are required thus making such trials highly complex and cost-intensive. However, regarding the potential relevance of chemoprevention on public health, further efforts to identify nutritional factors affecting prostate cancer growth are warranted.
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PMID:Nutrition and prostate cancer. 1146 7

Prostate cancer chemoprevention is defined as the administration of natural and synthetic agents that inhibit >/=1 steps in the natural history of prostate carcinogenesis. The goal is to find agents that modulate the progression from normal epithelium to dysplasia to high-grade prostatic intraepithelial neoplasia (HGPIN) to locally invasive cancer and systemic disease. Another important goal for chemoprevention is the maintenance of an androgen-sensitive clinical state and delay of the emergence of androgen independence. There is a strong rationale for androgen deprivation therapy (ADT) as a chemoprevention strategy for prostate cancer based on evidence from epidemiologic, experimental, molecular pathophysiologic, and randomized, controlled clinical trials. This includes the fact that HGPIN, the most likely precursor of invasive cancer, is androgen dependent and responds to ADT. Although the large, phase-3 Prostate Cancer Prevention Trial (PCPT) of finasteride versus placebo has established the feasibility and role of ADT for primary prevention, nevertheless, limitations of the anticipated treatment-effect size (eg, 25% reduction) and the potential for selection of androgen resistance provide incentive for finding other effective chemopreventive agents. The availability of novel noncytotoxic pharmaceutical and natural products in clinical development create opportunities for improving the therapeutic index through the principles of combination therapy. The emergence of new powerful tools, such as gene chip complementary DNA microarrays for multiplex gene expression profiling, will accelerate the identification of new molecular targets and the design of rational combinations. Several agent classes have a strong basis for combination with ADT, including antiproliferatives, antioxidant micronutrients (selenium), antiestrogens, and nonsteroidal anti-inflammatory drugs (selective cyclooxygenase-2 inhibitors).
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PMID:Androgen deprivation therapy for prostate cancer chemoprevention: current status and future directions for agent development. 1150 57

The effects of selenium exposure were studied in LNCaP human prostate cancer cells, and this same cell line adapted to selenium over 6 months to compare acute versus chronic effects of sodium selenite, the latter most closely resembling human clinical trials on the effects of selenium in cancer prevention and therapy. Our results demonstrated that oxidative stress was induced by sodium selenite at high concentrations in both acute and chronic treatments, but outcomes were different. After acute exposure to selenite, cells exhibited mitochondrial injury and cell death, mainly apoptosis. After chronic exposure to selenite, cells showed growth inhibition caused by cell cycle arrest, increased numbers of mitochondria and levels of mitochondrial enzymes, and only minimal induction of apoptosis. Immunoblotting analysis revealed that multiple proteins were up-regulated by chronic exposure to selenite. Among them, only up-regulation of manganese superoxide dismutase and the cyclin-dependent kinase inhibitor p21(Waf1/Cip1), proteins known to be redox sensitive and to have cell cycle regulatory functions, correlated with cell growth inhibition. Our results in selenite-adapted cells suggest that selenium may exert its effects in human prostate cancer cells by altering intracellular redox state, which subsequently results in cell cycle block.
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PMID:Redox-mediated effects of selenium on apoptosis and cell cycle in the LNCaP human prostate cancer cell line. 1158 38

Epidemiological studies have suggested that low levels of selenium are associated with a higher incidence of both lung and prostate cancer. We analyzed the selenium serum concentration in 356 Carotene and Retinol Efficacy Trial (CARET) participants who later developed lung cancer and 356 matched controls and in 235 prostate cancer cases and 456 matched controls. Serum samples were obtained a mean of 4.7 years before diagnosis for both tumor types. Controls were matched to cases by year of randomization, age, smoking status, treatment arm, exposure population (asbestos workers or cigarette smokers), and year of blood draw. In the control population (n = 820), significant predictors of low serum selenium concentration were current smoking status and East Coast locations of the study center. Overall, there was no significant difference in mean serum selenium in lung cancer cases versus controls (11.91 microg/dl versus 11.77 microg/dl) or prostate cancer cases versus controls (11.48 microg/dl versus 11.43 microg/dl). No statistically significant trend in odds ratio was seen across quartiles of serum selenium for lung cancer (P = 0.49) or prostate cancer (P = 0.69). In a subpopulation of 174 prostate cancer patients who had clinical and pathological staging material reviewed, there was no association between serum selenium and Gleason score or clinical or pathological stage. In the CARET population of current and former smokers consuming an ad libitum diet, the serum concentration of selenium was not a risk factor for either lung cancer or prostate cancer.
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PMID:Predictors of serum selenium in cigarette smokers and the lack of association with lung and prostate cancer risk. 1158 33

The dramatic international variation in prostate cancer mortality rates suggest an environmental influence. This combined with a building understanding of the genetic mechanisms of carcinogenesis encourages a search for ways to prevent it. Androgenic stimulation over a period of time has been suggested a cause of prostate cancer. The corollary to this hypothesis is that lowering androgenic stimulation over time will prevent prostate cancer. Decreasing androgenic stimulation of the prostate with 5-alpha-reductase inhibitors such as finasteride has been shown to decrease prostate size and may prevent prostate cancer. A large, long-term clinical trial is underway using finasteride to determine if it can prevent prostate cancer. Results are expected in 2004. Epidemiologic and laboratory studies also suggest that high selenium and vitamin E intake lowers risk of prostate cancer. Recent serendipitous findings of two randomized clinical trials support the hypothesis that selenium and vitamin administration will decrease prostate cancer risk. A study to assess these compounds is beginning. Other promising, but less developed, interventions in chemoprevention of prostate cancer include vitamin D supplementation and diet modification. All will need to be rigorously evaluated before they can be advocated for prostate cancer prevention.
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PMID:The future of prostate cancer prevention. 1179 34

Several important clinical trials under way at the Arizona Cancer Center seek to build on the results of Clark's 1996 study of selenium and decreased risk of prostate cancer. Those results, an unanticipated end point of a clinical trial, suggest that selenium has significant preventive power. The studies under way involve continued follow-up of the study cohort that generated the 1996 results and trials of selenium among men with negative biopsies, men with high-grade prostatic intraepithelial neoplasia, men with prostate cancer treated with selenium before prostatectomy, and men with prostate cancer who have chosen watchful waiting rather than active intervention. These studies promise important opportunities to validate Clark's original results.
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PMID:Larry Clark's legacy: randomized controlled, selenium-based prostate cancer chemoprevention trials. 1179 27

Selenium and vitamin E are probably 2 of the most popular dietary supplements considered for use in the reduction of prostate cancer risk. This enthusiasm is reflected in the initiation of the Selenium and Vitamin E Chemoprevention Trial (SELECT). Is there sufficient evidence to support the use of these supplements in a large-scale prospective trial for patients who want to reduce the risk of prostate cancer? Results from numerous laboratory and observational studies support the use of these supplements, and data from recent prospective trials also add partial support. However, a closer analysis of the data reveals some interesting and unique associations. Selenium supplements provided a benefit only for those individuals who had lower levels of baseline plasma selenium. Other subjects, with normal or higher levels, did not benefit and may have an increased risk for prostate cancer. The concept that supplements reduce prostate cancer risk only in those at a higher risk and/or those with lower plasma levels of these compounds is supported by trials examining beta-carotene supplements. Smokers may be the only individuals who benefit, as has also been shown with vitamin E supplementation. In 4 recent prospective studies, vitamin E was found to reduce the risk of prostate cancer in past/recent and current smokers and those with low levels of this vitamin. Vitamin E supplements in higher doses (> or =100 IU) were also associated with a higher risk of aggressive or fatal prostate cancer in nonsmokers from a past prospective study. The dose of vitamin E in the SELECT trial (400 IU/day) is 8 times higher than what has been suggested to be effective (50 IU/day) by the largest randomized prospective trial in which the incidence rate of prostate cancer was used as an endpoint. Recent research also suggests that dietary vitamin E may be associated with a lower risk of prostate cancer than the vitamin E supplement. Additionally, recent results from all past cardiovascular prospective, randomized trials suggest that vitamin E shows little benefit for cardiovascular disease risk, especially at the dose being used in the SELECT trial. Other intriguing positive findings from past prospective studies of supplements suggest that aspirin and other nonsteroidal anti-inflammatory drugs have a role in reducing the risk of prostate cancer or other types of cancer (eg, colon cancer). It may be time to conduct a large costly trial to reconsider the use of selenium and vitamin E supplements for the reduction of prostate cancer risk. Some evidence for the use of these supplements exists, but serious embellishment of study findings may be leading to an inappropriate use of these supplements in a clinical setting.
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PMID:Selenium and vitamin E supplements for prostate cancer: evidence or embellishment? 1193 32


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