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Two stages of cancer prevention with green tea.

Cancer chemoprevention is a new and important medical science in its own right. On the occasion of my presentation entitled "Natural agents and cancer chemoprevention" at the 90th AACR Meeting in 1999, I summarized our recent results on cancer prevention with green tea. In this article, the present status of clinical trials supported by the Chemoprevention Branch of the National Cancer Institute in the United States is first described by way of introduction. Although various natural products are now under investigation in phase I clinical trials, green tea has, perhaps, the greatest potential for further development. In order to expand our understanding of the effects of tea polyphenols and green tea, I review their ability to inhibit growth and cause apoptosis of cancer cells, their distribution into target organs and their other cancer-preventing properties. In addition, the paper focuses on the significance of reducing tumor necrosis factor alpha (TNFalpha) gene expression in cells and TNFalpha release from cells as essential activities for cancer prevention. As for the amounts of green tea effective in cancer prevention, I present two results from our Research Institute: a prospective cohort study with over 8000 individuals in Saitama Prefecture revealed that the daily consumption of at least ten Japanese-size cups of green tea resulted in delayed cancer onset, and a follow-up study of breast cancer patients conducted at our Hospital found that stages I and II breast cancer patients consuming over five cups per day experienced a lower recurrence rate and longer disease-free period than those consuming fewer than four cups per day. Thus, I propose here, for the first time, the two-stage approach to analyzing cancer prevention with green tea: cancer prevention before cancer onset and cancer prevention following cancer treatment. As an additional example of cancer prevention with natural agents, kava, a daily beverage in Fiji, is mentioned. All the evidence reminds us of the significance of alternative medicine in practical cancer prevention.

Adult↗

Mechanisms of disease: Inflammatory mediators and cancer prevention.

Discovery of molecular pathways critical to carcinogenesis is revolutionizing the treatment and prevention of cancer. Traditional chemotherapeutic approaches usually cause 'global' cytotoxicity to both normal and carcinoma cells. Over the past decade, however, investigators have developed compounds that inhibit tumor formation more selectively by targeting specific signaling pathways, including those involving the epidermal growth factor receptor (EGFR) and cyclooxygenase 2 (COX2). COX2-derived bioactive lipids, including prostaglandin E2, are potent inflammatory mediators that promote tumor growth and metastasis through stimulation of cell proliferation, invasion, and angiogenesis. Recent work has demonstrated significant crosstalk between the COX2 and EGFR pathways, while preclinical data demonstrates a synergistic effect when both pathways are targeted simultaneously. Combination therapy, a common strategy in cancer treatment, is likely to improve outcomes in cancer prevention as well. Ongoing clinical trials designed to assess whether low doses of COX2 and EGFR inhibitors used in combination could prove more effective and result in reduced toxicity than either agent alone may provide new options for cancer prevention and treatment. We discuss advances in cancer prevention by focusing on mechanisms by which bioactive lipids contribute to tumor formation. While cancer chemoprevention is a relatively young field, we argue that this approach to malignant disease bears significant potential.

Humans↗

Clinical trials of vitamin and mineral supplements for cancer prevention.

Approximately 20-30% of Americans consume multivitamin supplements daily, indicating high public interest in the prevention of cancer and other chronic diseases through a nutrition-based approach. Although several bioactive food components, including vitamins and minerals, have been investigated for their ability to affect cancer risk, few large, randomized, placebo-controlled clinical trials of multivitamins with cancer as the primary endpoint have been performed. The results of most large-scale trials of multivitamin supplements (combinations of > or = 2 vitamins and minerals) to prevent cancer have been mixed. The Linxian General Population and Dysplasia trials found a decreased risk of cancer, particularly stomach cancer, for participants taking a multivitamin supplement, but this was in a borderline-deficient population in China. Two trials, the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study and the beta-Carotene and Retinol Efficacy Trial, found an increased risk of lung cancer among male cigarette smokers or asbestos-exposed persons taking beta-carotene-a surprising result, considering that most epidemiologic studies have suggested that consumption of fruit and vegetables appears to lower cancer risk. To clarify the effects of multivitamin supplements, several large randomized clinical trials are underway, including the Physicians' Health Study II, the Selenium and Vitamin E Cancer Prevention Trial, and a European study, Supplémentation en Vitamines et Minéraux Antioxydants (SU.VI. MAX). Because epidemiologic studies generally evaluate foods rather than specific bioactive food components, a systematic approach to determining how combinations of vitamins and minerals may interact to ameliorate cancer risk is necessary to further our understanding of the potential benefits and risks of supplement use.

Dietary Supplements↗

Dietary and Chemoprevention Strategies for Breast Cancer Prevention.

Breast cancer is the most common cancer among American women. Strategies to eliminate or cure invasive breast cancer (eg, treatment of established disease and early detection) have been joined by a promising new approach, prevention. Epidemiologic studies have yet to demonstrate that dietary modification can reduce the risk of breast cancer, but important trials are ongoing. The chemoprevention program of the National Cancer Institute (NCI) has been underway for a decade. The discovery of biomarkers, or "intermediate endpoints," that can serve as surrogates for the ultimate endpoint, breast cancer, is crucial to the success of this program. The chemoprevention programs of NCI and the Division of Cancer Prevention and Control have identified promising cancer prevention compounds, many of which are being studied in clinical trials.

Journal Article↗

Possible role for green tea in ovarian cancer prevention.

Ovarian cancer is the leading cause of death from gynecologic cancer. Tea, especially green tea, has shown promise in the prevention of several cancers. Green tea contains a number of compounds, including polyphenols, that have chemopreventive properties. There is much evidence from in vitro and animal studies suggesting that components of tea are associated with decreased risk or progression of ovarian cancer. However, epidemiologic studies have generated inconsistent results. Recent research conducted in China reported reduced risk of ovarian cancer and increased survival post diagnosis with green tea consumption. This review presents emerging evidence and the authors' perspectives on the role of green tea in ovarian cancer prevention.

Animals↗

An Estimate of the Potential for Cancer Prevention in Japan.

Cancer prevention is an important strategy in cancer control and it consists of primary prevention and secondary prevention. Major avoidable or manageable risk factors for cancer identified from previous studies are tobacco, diet and infection. Some cancer could be prevented by controlling those risk factors. In Japan screenings for gastric cancer, cervical cancer, lung cancer, breast cancer and colo-rectal cancer have been widely conducted under the Law of Health Maintenance for the Aged. In planning and evaluating cancer control activities in Japan, it was considered useful to estimate the potential of primary and secondary prevention of cancer. The author estimated the potential of cancer prevention in Japan twice previously in 1990 and 1999. In this paper the potential of cancer prevention in Japan was re-estimated by using a different method and more recent data. From the present study it was estimated that about 25% of cancer occurrence could be prevented by control of smoking, diet and infection, about 9-15% of cancer deaths could be prevented by cancer screening, and about 6- 10 % of cancer deaths could be prevented by application of the state-of-the art diagnosis and treatment of cancer, altogether about 40-50% of cancer occurrences/deaths could be prevented if all possible measures for cancer prevention are applied to the general public and cancer patients in Japan.

Journal Article↗

Preventing cancer, cardiovascular disease, and diabetes: a common agenda for the American Cancer Society, the American Diabetes Association, and the American Heart Association.

Collectively, cardiovascular disease (including stroke), cancer, and diabetes account for approximately two thirds of all deaths in the United States and about 700 billion dollars in direct and indirect economic costs each year. Current approaches to health promotion and prevention of cardiovascular disease, cancer, and diabetes do not approach the potential of the existing state of knowledge. A concerted effort to increase application of public health and clinical interventions of known efficacy to reduce prevalence of tobacco use, poor diet, and insufficient physical activity-the major risk factors for these diseases-and to increase utilization of screening tests for their early detection could substantially reduce the human and economic cost of these diseases. In this article, the ACS, ADA, and AHA review strategies for the prevention and early detection of cancer, cardiovascular disease, and diabetes, as the beginning of a new collaboration among the three organizations. The goal of this joint venture is to stimulate substantial improvements in primary prevention and early detection through collaboration between key organizations, greater public awareness about healthy lifestyles, legislative action that results in more funding for and access to primary prevention programs and research, and reconsideration of the concept of the periodic medical checkup as an effective platform for prevention, early detection, and treatment.

Cardiovascular Diseases↗

Trial of retinol and isotretinoin in skin cancer prevention: a randomized, double-blind, controlled trial. Southwest Skin Cancer Prevention Study Group.

The objective of this study was to examine the effect of retinol and isotretinoin on the incidence of nonmelanoma skin cancer in high-risk subjects. A total of 525 participants with a history of at least four basal cell carcinomas (BCCs) and/or cutaneous squamous cell carcinomas (SCCs) were entered into a randomized, double-blind, placebo-controlled trial, performed in free-standing study clinics. Participants were randomly assigned to receive oral retinol (25,000 units), isotretinoin (5-10 mg), or placebo supplementation daily for 3 years. The time to first new occurrence of BCC or cutaneous SCC was used as the outcome measure. During the study period, 319 BCCs and 125 cutaneous SCCs were diagnosed clinically and pathologically. There were no differences between those who received retinol, isotretinoin, or the placebo, with regard to the time to first occurrence or to the total number of tumors noted. No beneficial effects were noted with regard to the prevention of nonmelanoma skin cancer with either retinol or isotretinoin.

Adult↗

Cancer prevention and early detection program for educators: reducing the cancer burden of among African Americans within the academic arena.

In anticipation of the need for nurses to have a strong base of knowledge and skill relative to cancer prevention and cancer control, academic institutions across the profession are being strongly encouraged by oncology nurse leaders to intensify their efforts to integrate didactic, laboratory and clinical experiences that address cancer prevention and control within nursing curricula. However, minimal attention is given to cancer prevention, risk reduction and screening in most nursing education, training, and professional development programs. The same is true relative to the incorporation of discussions, activities and experiences in clinical settings that facilitate an understanding of issues specific to cancer prevention and control racially/ethnically diverse, in high-risk, and medically underserved population groups. In an attempt to address this gap in nursing education, a Cancer Prevention and Early Detection Program for Nurse Educators was developed. Funded by a grant by the National Institutes of Health National Cancer Institute, the program aimed to provide nurse educators with state-of-the-science information and resources relative to the prevention and control of cancers in African-Americans. This report provides a summary of the programs aims, objectives, impact and outcomes.

Adult↗

The Forsyth County Cervical Cancer Prevention Project--I. Cervical cancer screening for black women.

The Forsyth County Cervical Cancer Prevention Project was a 5 year National Cancer Institute-funded community-based public health education program implemented to address the problem of excess mortality from cervical cancer among black women in Forsyth County, North Carolina. The intervention was a community-based public health education program that included mass media, direct education workshops, and provision of education on cervical cancer and screening to health care providers. The intervention was implemented from November 1988 to September 1991. Evaluation of the community intervention used a quasi-experimental design, with Forsyth County, North Carolina, receiving the program and Durham County, North Carolina, serving as the control. Comparison of pre- and post-intervention telephone survey data revealed that, overall, awareness of cervical cancer and the Pap smear increased. Knowledge, attitudes and behaviors showed little change, considering those interviewed in aggregate. Among women defined as high-risk (elderly, low socioeconomic status, public health clinic patients and/or those who do not receive regular care), a significant trend toward greater participation in screening was detected for the 6 month period following the intervention. These results suggest that awareness of cervical cancer can be increased by public health education, but that the additional attention coming to patients through the actions of health care providers and health care delivery systems may supply the additional input needed to produce behavior change.

Adolescent↗

Adapting postdoctoral training to interdisciplinary science in the 21st century: the Cancer Prevention Fellowship Program at the National Cancer Institute.

Preparing junior scientists for careers in the health sciences has become an immense challenge for many reasons, including the emerging demand for multidisciplinary approaches to solving problems in the health sciences. For those choosing careers in hybrid and interdisciplinary fields, the "traditional" postdoctoral training model may not perform well, particularly in light of other problems that plague postdoctoral success. New approaches are required. Using the interdisciplinary field of cancer prevention as an example, the authors describe the Cancer Prevention Fellowship Program (CPFP) of the National Cancer Institute, a three-year postdoctoral program of which the goal is to provide its fellows with a strong foundation in cancer prevention through education, mentored research, and structured professional development training activities that emphasize multidisciplinary approaches and leadership skills. Over time, the CPFP has incorporated the best aspects of the traditional postdoctoral training model with newer training approaches in an effort to overcome existing problems in postdoctoral training and to address the additional complexities inherent in training those who seek careers in interdisciplinary science. Many aspects of the CPFP, including an efficient infrastructure, a dedicated staff, a capacity to provide educational activities, and the provision of rich research opportunities, may translate well to other postdoctoral programs that face similar issues.

Education, Medical, Graduate↗

Volunteers as adjunct researchers in a cancer prevention trial: the American Cancer Society Colon Polyp Prevention Study.

BACKGROUND: In April 1991, the Virginia Division of the American Cancer Society (ACS) initiated the feasibility phase of the Colon Polyp Prevention Study (CPPS) to determine whether a high fiber supplement would decrease new adenomatous colorectal polyp occurrence. The feasibility phase had two specific objectives: 1) to evaluate accrual and compliance to the designed protocol and 2) to evaluate and demonstrate the effectiveness of volunteers as research assistants. The CPPS is an innovative project in which trained volunteers play a significant role in the research process. METHODS: In the CPPS, volunteer adjunct researchers (VARs) were trained to perform individual dietary data collection and intervention and other general study monitoring functions. VARs were trained, certified, and monitored in the performance of their assigned tasks by ACS staff and expert consultants. RESULTS: A total of 119 volunteers were trained as VARs, 74 of whom were certified and matched to a study participant. Between 1991-1995, only six VARs left the study. After active accrual of participants to the study ceased in 1995, 38 VARs (50% of the certified VARs) continued to monitor the active study participants. All VARs were consistently able to conduct the functions for which they were trained. CONCLUSIONS: In spite of expected volunteer attrition rates, a core of 38 dedicated VARs were matched to 72 participants and demonstrated the ability to perform selected data collecting activities on a consistent and efficient basis. The use of trained volunteers has allowed the CPPS to function in its feasibility phase at personnel cost considerably less than that of other similar cancer prevention trials.

American Cancer Society↗

A clinical cancer prevention curriculum in a comprehensive cancer center.

Interns, residents, and medical students who spend one month at a comprehensive cancer center are presented with a strategy to incorporate cancer preventive services into their outpatient practices. This is accomplished through didactic lectures in clinical epidemiology. Terms that are essential to an understanding of disease occurrence are defined including incidence, prevalence, and mortality rate. Odds and probability are explored with the introduction of the odds ratio and the identification of risk factors. Primary and secondary cancer prevention are defined, and parameters related to cancer screening are introduced (sensitivity, specificity, prevalence, and positive predictive value). Risk factors for malignancy are identified where they are known and can be modified. Primary prevention strategies are reviewed by site along with data that support or refute recommendations for site-specific screening. Medical conditions and risk factor profiles that define high-risk groups are reviewed. Trainees are given copies of the US Preventive Services Task Force screening recommendations and a clinical handbook. The impact of this information on clinical practice patterns remains to be evaluated.

Cancer Care Facilities↗

Future possibilities in the prevention of breast cancer: breast cancer prevention trials.

The available results from breast cancer chemoprevention trials are reviewed. Four trials using tamoxifen have been performed, of which three have reported efficacy results. A fifth trial using raloxifene has also been reported. The largest tamoxifen trial showed approximately 50% reduction in breast cancer incidence in the short term, but the two smaller trials did not find any reduction. Greater agreement exists for side effects; incidences of thromboembolic disease and endometrial cancers are raised approximately threefold when tamoxifen is used for 5 years. The possible reasons for the discrepancy in breast cancer reduction are explored. A review of trial parameters does not clearly explain this difference, and a meta-analysis indicates that all results are compatible with a 40% reduction in short-term incidence. Several important questions remain regarding the clinical implications of this result, including the effect on mortality, the appropriate risk groups for chemoprevention and the long-term effects on incidence. Continued follow up of these trials is crucial for resolving these issues.

Adult↗

Physical activity and cancer prevention: etiologic evidence and biological mechanisms.

Scientific evidence is accumulating on physical activity as a means for the primary prevention of cancer. Nearly 170 observational epidemiologic studies of physical activity and cancer risk at a number of specific cancer sites have been conducted. The evidence for decreased risk with increased physical activity is classified as convincing for breast and colon cancers, probable for prostate cancer, possible for lung and endometrial cancers and insufficient for cancers at all other sites. Despite the large number of studies conducted on physical activity and cancer, most have been hampered by incomplete assessment of physical activity and a lack of full examination of effect modification and confounding. Several plausible hypothesized biological mechanisms exist for the association between physical activity and cancer, including changes in endogenous sexual and metabolic hormone levels and growth factors, decreased obesity and central adiposity and possibly changes in immune function. Weight control may play a particularly important role because links between excess weight and increased cancer risk have been established for several sites, and central adiposity has been particularly implicated in promoting metabolic conditions amenable to carcinogenesis. Based on existing evidence, some public health organizations have issued physical activity guidelines for cancer prevention, generally recommending at least 30 min of moderate-to-vigorous intensity physical activity on > or =5 d/wk. Although most research has focused on the efficacy of physical activity in cancer prevention, evidence is increasing that exercise also influences other aspects of the cancer experience, including cancer detection, coping, rehabilitation and survival after diagnosis.

Breast Neoplasms↗