Tamoxifen and Rolaxifene pills
phoot by Bill Branson, NCI

According to the CDC's Center for Cancer Prevention and Control1, cancer prevention can come in the form of early screening for some cancers, receiving some vaccines, and risk reduction through routine medical care and lifestyle changes. One form of cancer prevention is known as chemoprevention.

The National Cancer Institute lists over three dozen agents currently being researched for their chemopreventive potential2, but perhaps the two most well known chemopreventive agents are tamoxifen, a selective estrogen receptor modulator (SERM) used to prevent breast cancer in women, and finasteride, a 5 alpha-reductase inhibitor used to prevent prostate cancer in men.

What it's effective for and why

Chemoprevention is proactive cancer treatment for people who do not have cancer but who are determined to be at high risk for developing certain cancers. This risk may be elevated because of a pre-cancerous medical condition, because of one's lifestyle, or because of one's family history. For instance, finasteride reduces the body's production of the hormone testosterone, while tamoxifen blocks the effects of the hormone estrogen in the breast. Currently, a class of drugs known as COX-2 inhibitors are under investigation for their chemopreventive potential against both breast and colorectal cancers3.

Risks and side effects: Overview

Chemopreventive drugs do come with risks and side effects. For instance, tamoxifen has been shown to increase the risk of developing endometrial cancer, cataracts, and blood clots, which is why the drug is considered most beneficial to woman under the age of 504.

Unfortunately, chemopreventive agents face serious hurdles. Many people scoff at the idea of taking a drug for a disease they do not yet have (and may never develop). Furthermore, many doctors either disagree with the published studies regarding chemopreventive drugs, or they are even aware of their existence5.


  1. CDC: Center for Cancer Prevention and Control
  2. NCI Division of Cancer Prevention: Chemopreventive agents
  3. National Cancer Institute: Chemoprevention
  4. NCI: Selective estrogen receptor modulators
  5. Hamilton RJ et al. "Knowledge and use of finasteride for the prevention of prostate cancer." Cancer Epidemiol Biomarkers Prev 2010; DOI: 10.1158/1055-9965.EPI-10-0082.


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