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At least 73 records · Page 4Linked to original sources
PubMed2001

Cardiovascular effects of tamoxifen in women with and without heart disease: breast cancer prevention trial. National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial Investigators.

BACKGROUND: The overall effect of prophylactic tamoxifen in women depends on the balance between the effects of the drug, which include preventing breast cancer and altering cardiovascular risk. In a recent clinical trial, postmenopausal estrogen-progestin therapy was shown to increase the risk of early cardiovascular events among women with a history of coronary heart disease (CHD). The cardiovascular effects of tamoxifen in women with and without CHD are not known. The National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial (BCPT) is the only clinical trial that provides data to assess the cardiovascular effects of tamoxifen in women with and without CHD. METHODS: A total of 13 388 women at increased risk for breast cancer were randomly assigned in the BCPT to receive either tamoxifen (20 mg/day) or placebo. Cardiovascular follow-up was available for 13 194 women, 1048 of whom had prior clinical CHD. Fatal and nonfatal myocardial infarction, unstable angina, and severe angina were tabulated (mean follow-up: 49 months). All statistical tests were two-sided. RESULTS: Cardiovascular event rates were not statistically significantly different between women assigned to receive tamoxifen and those assigned to receive placebo, independent of pre-existing CHD. Among women without CHD (6074 on tamoxifen versus 6072 on placebo), risk ratios (95% confidence intervals [CIs]) for tamoxifen users were 1.75 (0.44 to 8.13) for fatal myocardial infarction, 1.11 (0.55 to 2.28) for nonfatal myocardial infarction, 0.69 (0.29 to 1.57) for unstable angina, and 0.83 (0.32 to 2.10) for severe angina. In women with CHD (516 on tamoxifen versus 532 on placebo), risk ratios (95% CIs) for tamoxifen users were 0.00 (0 to 1.58) for fatal myocardial infarction, 1.25 (0.32 to 5.18) for nonfatal myocardial infarction, 2.26 (0.87 to 6.55) for unstable angina, and 1.39 (0.23 to 9.47) for severe angina. There was no evidence that the lack of association between tamoxifen and cardiovascular events was related to an early increase in risk that may have been offset by a late decrease in risk. CONCLUSION: When used for breast cancer prevention in women with or without heart disease, tamoxifen is not associated with beneficial or adverse cardiovascular effects.

Angina Pectoris↗
PubMed1993

Training researchers in cancer prevention and control: a description and evaluation of NCI's Cancer Prevention Fellowship Program.

NCI's Cancer Prevention Fellowship Program recently initiated a continuing evaluation of the fellows' demographics, fellows' accomplishments in the program, fellow and preceptor expectations and satisfaction, program strengths and weaknesses, current employment for former fellows, and ex-fellows' perceptions of program training. Evaluation shows that the program attracts quality applicants (including minorities and females) nationwide from many disciplines. The program successfully educates about cancer prevention and provides a positive preceptor experience with publication opportunities. Areas for improvement are data access, stipend, office space, job assistance, and networking. Recommendations for other programs include committed enthusiastic staff; adequate budget, space, and support; a formal learning experience in public health fundamentals, research methods, and cancer prevention; individual mentored research within a productive scientific program; aggressive recruitment; competitive admissions policy; defined objectives for fellows; and ongoing formal program evaluation.

Attitude of Health Personnel↗
PubMed2005

Assessing benefit and risk in the prevention of prostate cancer: the prostate cancer prevention trial revisited.

PURPOSE: The Prostate Cancer Prevention Trial demonstrated a 25% reduction in period prevalence of prostate cancer in men randomly assigned to 5 mg/d of finasteride. However, widespread use of finasteride for prevention is inhibited by the observed increased risk of high-grade disease. We present a model of risk and benefit that estimates the potential effects of histologic artifact in the assignment of excess risk for high-grade disease and the possible effect of overdetection bias introduced by finasteride-induced volume reduction. METHODS: The absolute benefit/absolute risk ratio of finasteride use was estimated by calculating the ratio of absolute risk reduction in the finasteride arm to the absolute risk of excess high-grade cancers. This ratio was recalculated for assumptions that 10%, 25%, or 50% of the excess high-grade cancers were due to histologic artifact, and that there was a 25% overdetection bias in the finasteride arm. RESULTS: For all cancers the absolute benefit/absolute risk ratio increased from 4.6:1 to 5.1:1, 6.2:1, and 9.2:1 for assumptions of 10%, 25%, or 50% histologic artifact, respectively. The ratio increased from 4.6:1 to 8.2:1 for the assumption of 25% overdetection bias, and to 9.1:1, 10.9:1, and 16.3:1 for combined assumptions of 25% overdetection bias and 10%, 25%, or 50% histologic artifact, respectively. CONCLUSION: The adoption of a prevention strategy hinges on potential benefits weighed against potential risks. This model demonstrates the magnitude of effect for a hypothesized range of histologic artifact and overdetection bias on the assessment of risk versus benefit for finasteride.

Adenocarcinoma↗
PubMed2000

Future possibilities in the prevention of breast cancer: role of genetic variation in breast cancer prevention.

Risk factors for breast cancer are related to endogenous hormones and reproductive events. As such, traditional cancer prevention strategies are not easily applicable. Tamoxifen and other selective estrogen receptor modulators (SERMs) offer a new preventive strategy for some high-risk women, but have not yet been shown to be efficacious for all women. New tools to identify high-risk women are needed. One such tool is the development of a multigenic model of breast cancer susceptibility that can be used to screen women in order to identify those who carry a combination of alleles that puts them at significantly increased risk.

Adult↗
PubMed2003

Detoxifying cancer causing agents to prevent cancer.

Different vitamins and other micronutrients in vegetables, fruits, and other natural plant products may prevent cancer development (carcinogenesis) by interfering with detrimental actions of mutagens, carcinogens, and tumor promoters. The goal of current studies in cancer prevention is to determine the mechanisms of synergistic action of the natural source compounds known to inhibit one or more stages of carcinogenesis, that is, initiation and promotion/progression. Many natural cancer preventive agents are effective inhibitors of tumor initiation, promotion, and/or progression. The mechanism of action is related to their abilities to prevent critical carcinogen metabolism and to increase detoxification of carcinogens and tumor promoters. The authors review here the potential role of the detoxification system and, in particular, the roles of D-glucaric acid and the enzyme beta-glucuronidase in early detection and prevention of cancer. There is now growing evidence for the possible control of different stages of the cancer induction by inhibiting beta-glucuronidase with D-glucaric acid derivatives, especially with its salts (D-glucarates). D-Glucaric acid has been found in many vegetables and fruits. Therefore, the consumption of fruits and vegetables naturally rich in D-glucaric acid or self-medication with D-glucaric acid derivatives such as calcium D-glucarate offers a promising cancer prevention approach.

Animals↗
PubMed1997

Experimental evidence for cancer preventive elements in foods.

The last decade has witnessed an incredible advance in our understanding of how fruits and vegetables work to prevent cancer. Epidemiological studies have suggested that a diet rich in fruits and vegetables is associated with reduced risk for a number of common cancers. Food chemists and natural product scientists have identified hundreds of 'phytochemicals' that are being evaluated for the prevention of cancer. Food components can modify carcinogenesis in one of five different ways. They may: (1) modify carcinogen activation by inhibiting Phase 1 enzymes; (2) modify how carcinogens are detoxified through Phase 2 pathways; (3) scavenge DNA reactive agents; (4) suppress the abnormal proliferation of early, preneoplastic lesions; and (5) inhibit certain properties of the cancer cell.

Animals↗
PubMed2001

Follow-up of the breast cancer prevention trial and the future of breast cancer prevention efforts.

Women who are at increased risk for developing breast cancer can be identified using quantitative risk assessment models that provide valid estimates of risk. The Breast Cancer Prevention Trial (BCPT, P-1) demonstrated that tamoxifen can reduce the incidence of both invasive and noninvasive breast cancer as well as of bone fractures in women at increased risk. These benefits accrue at the expense of increased risk of endometrial cancer, thromboses, cataracts, and possibly diminished quality of life in postmenopausal women. All premenopausal women with a 5-year risk of developing invasive breast cancer greater than 1.67% derive net benefit from using tamoxifen to reduce the risk. Subset analyses of older postmenopausal women taking raloxifene for the treatment of osteoporosis indicate reduction of breast cancer incidence by more than 70%. These findings led the National Surgical Adjuvant Breast and Bowel Project (NSABP) to design and launch the STAR trial (P-2, the Study of Tamoxifen and Raloxifene). Eligible women are at least 35 years of age and postmenopausal, and they must have either lobular carcinoma in situ (LCIS) or a 5-year risk of invasive breast cancer of at least 1.67% as determined by the Gail model [M. H. Gail et al., J. Natl. Cancer Inst. (Bethesda), 81: 1879-1886, 1989]. Subjects are randomly assigned to receive either tamoxifen 20 mg or raloxifene 60 mg daily in a double-blind, double-dummy design. The trial is designed to recruit a total of 22,000 postmenopausal women and is powered to demonstrate superior efficacy of either agent or their equivalence in reducing the incidence of primary breast cancer. Additional end points will include the incidence of cardiovascular events and bone fractures. Thromboembolic events and endometrial cancer are the predicted toxicities. Ancillary studies of cognitive function will also be performed. Raloxifene should not be used for the reduction of breast cancer risk outside the context of the STAR trial.

Aged↗
PubMed2001

Epidemiological study on cancer prevention by ginseng: are all kinds of cancers preventable by ginseng?

In the light of experimental results, two case-control studies and one cohort study in a population of ginseng cultivation area were conducted to confirm whether ginseng has any anticarcinogenic effect on human cancers. All participants were interviewed using a standardised questionnaire to obtain the information on demographics, cigarette smoking, alcohol consumption and ginseng intake. In 905 pairs case-control study, 62% had a history of ginseng intake compared to 75% of the controls, a statistically significant difference (p<0.01). The odds ratio (OR) for cancer in relation to ginseng intake was 0.56. In extended case-control study with 1987 pairs, the ORs for cancer were 0.37 in fresh ginseng extract users, 0.57 in white ginseng extract users, 0.30 in white ginseng extract users, 0.30 in white ginseng powder users, and 0.20 in red ginseng users. Those who took fresh ginseng slices, fresh ginseng juice, and white ginseng tea, however, did not show decrease in the risk. Overall, the risk decreased as the frequency and duration of ginseng intake increased. With respect to the site of cancer, the ORs for cancers of the lip, oral cavity, pharynx, esophagus, stomach, colorectum, liver, pancreas, larynx, lung and ovary were significantly reduced by ginseng intake. Smokers with ginseng intake showed lower ORs for cancers of lung, lip, oral cavity and pharynx and liver than those without ginseng intake. In 5 yr follow- up cohort study conducted in the ginseng cultivation area, Kangwha-eup, ginseng intakers had significantly lower risk than non-intakers. As for the type of ginseng, cancer risk significantly decreased among intakers of fresh ginseng extract, alone or together with other ginseng preparations. Among 24 red ginseng intakers, no cancer death occurred during the follow-up period. The risk for stomach and lung cancers was significantly reduced by ginseng intake, showing a statistically significant dose-response relationship in each follow-up year. In conclusion, Panax ginseng C.A. Meyer has been established as non-organ specific cancer preventive, having dose response relationship. These results warrant that ginseng extracts and its synthetic derivatives should be examined for their preventive effect on various types of human cancers.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Nutritional interventions in cancer prevention.

The first generation of phase III nutritional intervention studies to prevent cancer has been completed. Nearly 150,000 total participants were studied in nine different interventions using randomized, double-blind, placebo-controlled designs that tested whether vitamins and/or minerals, given singly or in combination, could prevent total or site-specific cancer. The primary agents tested include beta-carotene, alpha-tocopherol, selenium, and retinol. This review summarizes the findings from the first generation of human experimental studies that tested micronutrients in the prevention of cancer, discusses lessons learned from these studies, identifies the most promising leads, and describes future prospects in nutritional intervention research.

Adult↗
PubMed1999

[Interventional trial for cancer prevention].

In cancer prevention studies, the methodology of the observational study (case-control study, cohort study) and interventional study were introduced. We established a protocol for an interventional randomized controlled trial for prevention of colorectal cancer. The subjects were 200 patients with multiple colorectal tumors (adenoma and/or early cancer). Two regimens were formulated for prevention of colorectal cancer. One was dietary guidance alone (Regimen I), and the other was dietary guidance plus the eating of wheat bran biscuits (Regimen II). The main end point of the trial is recurrence of colorectal tumors after 2 and 4 years. During the 4 years, 115 patients were recruited for Regimen I and 116 patients for Regimen II who agreed to participate in this trial.

Case-Control Studies↗
PubMed1986

Design of cancer prevention studies.

Cancer prevention in the past has referred principally to activities and studies identifying and describing the causes of and risk factors related to cancer. Although these efforts, excellent as they are, still require some fine tuning, the time has come to apply what we know to reduce cancer incidence and mortality worldwide. The National Cancer Institute has embarked on a national course of targeted intervention research and control aimed at reducing cancer mortality by 50% by the end of this century. A large proportion of that goal is to be achieved through cancer prevention research and applications. This paper will discuss the details of that plan with special emphasis paid to smoking and dietary interventions.

Diet↗
PubMed2001

Mexico City physicians' awareness about cervical cancer prevention: implications for cancer screening.

BACKGROUND: In spite of an early cancer detection program (CCSP), Mexico has a mortality rate for cervical cancer of 16.5 per 100,000 women. METHOD: A cross-sectional study of 330 physicians at the Mexico City General Hospital evaluated their knowledge of the CCSP, etiology, diagnostic alternatives, and treatment guidelines. Variance analysis was the statistical procedure used. Replies to a questionnaire about cervical cancer prevention awareness were scored on a scale from 1 to 9. RESULTS: According to the awareness scale, the global average classification was 4.4, with 50% of the physicians scoring 4 or less. There was no difference in the CCSP knowledge scores of gynecologists (mean 4.92, 95% CI 4.2-5.3), oncologists (mean 4.85, 95% CI 4.3-5.5), pathologists (mean 5.23, 95% CI 4.9-5.6), and those in other specialties (mean 4.29, 95% CI 4.2-5.0), p > 0.05. Many respondents attributed CCSP's lack of effectiveness to public apathy (68.12%). CONCLUSIONS: The effectiveness of the CCSP can be improved by educating health professionals if this education is combined with elimination of obstacles to its use. More information is needed to justify revising how doctors are educated in terms of not only quality of the training but also the contents of pre- and postgraduate training programs.

Analysis of Variance↗
PubMed2005

Advocating for cervical cancer prevention.

Cervical cancer is a significant health problem among women in developing countries. Contributing to the cervical cancer health burden in many countries is a lack of understanding and political will to address the problem. Broad-based advocacy efforts that draw on research and program findings from developing-country settings are key to gaining program and policy support, as are cost-effectiveness analyses based on these findings. The Alliance for Cervical Cancer Prevention (ACCP) has undertaken advocacy efforts at the international, regional, national, and local levels to raise awareness and understanding of the problem (and workable solutions), galvanize funders and governments to take action, and engage local stakeholders in ensuring program success. ACCP experience demonstrates the role that evidence-based advocacy efforts play in the ultimate success of cervical cancer prevention programs, particularly when new screening and treatment approaches-and, ultimately, radically new approaches such as a human papillomavirus vaccine-are available.

Cost-Benefit Analysis↗
PubMed2001

Familiar drugs may prevent cancer.

Despite positive results in large scale chemoprevention trials, many physicians are unaware of the potential cancer preventive properties of drugs in common usage. The antioestrogen tamoxifen and the selective cyclo-oxygenase-2 inhibitor celecoxib have been licensed in the USA for the chemoprevention of breast and colorectal cancers respectively in selected high risk individuals. Similarly, folate and retinol have been shown to decrease the incidence of colorectal cancer and squamous cell carcinoma of the skin respectively in large scale intervention trials. Other retinoids have proved efficacious in the tertiary chemoprevention of cancers of the breast and head/neck. Epidemiological evidence also exists in favour of aspirin, non-steroidal anti-inflammatory drugs, and angiotensin converting enzyme inhibitors preventing certain cancers. Phytochemicals may represent less toxic alternatives to these agents. Although some of these drugs are available without prescription and most are not yet licensed for use in cancer chemoprevention, physicians and students of medicine should be aware of this accumulating evidence base. Practitioners should be amenable to patient referral to discuss complex issues such as risk estimation or potential benefit from intervention.

Angiotensin-Converting Enzyme Inhibitors↗
PubMedDate not supplied

Diallyl sulfide inhibits diethylstilbestrol-induced lipid peroxidation in breast tissue of female ACI rats: implications in breast cancer prevention.

Diallyl sulfide (DAS) is a component of garlic and prevents cancer in several animal models in various organs. The chemopreventive effects of DAS are attributed to modulation of enzymes to alter the bioactivation of xenobiotics. Diethylstilbestrol (DES) is a synthetic estrogen that causes breast cancer in female ACI rats subsequent to metabolism with concurrent free radical production. This study assessed the effect of DAS on DES-induced reactive oxygen species (ROS) using lipid peroxidation as an empirical endpoint. We have demonstrated that acute exposure to DES results in a significant increase in lipid hydroperoxides (LPH) in breast tissue and DAS attenuated DES-induced LPH concentrations. Two-week exposure to DES caused significant increases in LPH concentrations in breast and liver tissues. DES-induced LPH concentrations were decreased by coadministration of DAS at this time point. There were no statistical differences in the concentrations of LPH in breast and liver tissues of rats treated for 4/6 weeks with DAS/DES. These results demonstrate that DAS inhibits the production of ROS which suggests that DAS effectively inhibits DES bioactivation in female ACI rats which may have implications for chemopreventive intervention strategies. Our results suggest that garlic consumption might be useful for the prevention of human breast cancers.

Allyl Compounds↗
PubMed1993

Beta-carotene and vitamin E in oral cancer prevention.

The ultimate proof that a putative chemopreventive agent does prevent cancer is a demonstration of reduced cancer incidence in a targeted population. However, because of practical and logistical considerations, such trials are virtually impossible to conduct for the majority of cancers. Therefore, a conclusion regarding the efficacy of chemopreventive activity is based on consideration of a variety of indirect lines of evidence, including laboratory studies, animal model systems, epidemiologic surveys, intervention trials involving reversal of premalignant changes, and the prevention of malignancies in particularly high risk subjects. Furthermore, the only agents worth testing are those with limited, or preferably, no toxicity, since the final use will be prevention in a generally healthy population. Beta-carotene and vitamin E both fulfill all the criteria for suitable chemopreventive agents; several lines of evidence point toward preventive roles for them in oral cancer. In numerous epidemiologic studies, low intake of beta-carotene has been associated with higher cancer risk. Both intake and supplemental use of vitamin E have been associated with a lowered risk of cancer. Smokers, whose habit is a major risk factor, have lower beta-carotene levels in oral mucosal cells when compared with non-smokers. In several laboratory and animal model systems, including the very relevant hamster cheek pouch model, these agents strongly inhibit oral cavity carcinogenesis. Beta-carotene and vitamin E produce regression of oral leukoplakia, a premalignant lesion for oral cancer. This has now been shown in seven clinical trials: five with beta-carotene alone, one with vitamin E, and one with a combination of both.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗