Evidence from systematic evaluation of agent classes Chemopreventive agents can be identified by systematic evaluation of classes of agents that act at specific molecular targets, using laboratory assays to characterise their mechanisms of action with respect to cancer. Some agents that are studied by these so called mechanistic assays are signal transduction modulators, hormone modulators, and anti-inflammatories (which inhibit promotion and progression of neoplasia), antimutagens (which inhibit initiation), and antioxidants (which inhibit initiation and promotion).13 Such systematic evaluations can provide additional information on the chemopreventive potential of phytochemicals initially identified through epidemiological and laboratory research. Evidence from cancer treatment Strategies developed for the treatment of cancer have provided indications for the potential chemopreventive value of certain agents used in treatmentfor example, finasteride (a 5--reductase inhibitor used to treat benign prostatic hyperplasia) for prostate cancer and tamoxifen (a selective oestrogen receptor modulator) for breast cancer. Finasteride is being tested in a prostate cancer prevention trial in about 18 000 men aged over 55 whose concentrations of prostate specific antigen (PSA) are lower than 3 ng/ml and in whom a digital rectal examination was negative.14 The trial is designed to determine whether daily doses of finasteride can reduce the incidence of cancer over seven years. A breast cancer prevention trial was initiated in 1992 in response to data from trials in women with early breast cancer that indicated that treatment with tamoxifen resulted in a significant decrease (40-50%) of contralateral breast cancer.15 The trial, conducted with more than 13 000 women at increased risk of breast cancer because of age or other risk factors, was unblinded in 1998 when it was found that women who took tamoxifen daily for five years had a 49% reduced risk of breast cancer compared with those taking placebo.16 An ongoing study of tamoxifen and raloxifene aims to determine whether raloxifene, also a selective oestrogen receptor modulator, is as effective as tamoxifen in reducing the risk of breast cancer in postmenopausal women at high risk.17 The effects of agents such as tamoxifen underscore the sometimes vague boundary between prevention and treatment of cancer, an issue complicated by new findings in molecular biology that blur the distinctions between premalignant and malignant lesions.17 Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.