Vitamins and food-derived compounds are the focus of a large part of chemopreventive research, but a number of drugs being used

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问题     Vitamins and food-derived compounds are the focus of a large part of chemopreventive research, but a number of drugs being used for treatment may also be suitable for prevention. One such drug is tamoxifen, the anti-estrogen medication that has demonstrated great potency in the treatment of breast cancer. First synthesized in 1966 for birth-control research, tamoxifen is thought to thwart cancer by blocking estrogen receptors that, when occupied, stimulate cell proliferation.
    An on-going, 10-year study by a national collaborative group of US physicians and scientists and the National Cancer Institute is testing tamoxifen’ s ability to prevent breast cancer in thousands of healthy women who are at increased risk for the disease. In earlier studies of breast cancer patients, tamoxifen reduced the incidence of new tumors in the unaffected breast by about 40 percent. Those figures providing the rationale for investigating tamoxifen as preventive agent. But although it has clearly been a boon to breast cancer patients, tamoxifen has side effects, the most serious of which are increased risks of uterine cancer and blood-clot formation. Because of those risks, some women’ s health advocates have questioned the use of the compound by healthy women for prevention.
    Yet the knowledge gained from a large-scale preventive trial of tamoxifen could help researcher understand how to synthesize a second generation of anti-estrogen drugs having greater potency and fewer risks than those associated with tamoxifen itself.
    We have every reason to believe that the power of chemoprevention is sure to grow as researchers continue to identify promising new chemoprevention agents and clinical trials begin to provide insights into these substances’ effects in humans. With the advance of these investigations and our greater understanding of cancer, chemoprevention will undoubtedly play a major role in reducing cancer incidence as well as the number of deaths caused by the disease.
Where is this passage most probably taken from?

选项 A、A medical student’ s homework.
B、A medical journal.
C、A medical textbook.
D、Leaflet of a drug manufacturer.

答案B

解析
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