Epidemological evidence shows statins protect against breast and other cancers.

Drugs used to lower cholesterol levels may have unexpected benefits: some statins may also reduce the risk of breast and other cancers, according to evidence from six large epidemiological studies.

Statins cut the risk of breast, pancreatic, prostate and lung cancer by about 50%, scientists reported at cancer meetings in April and May. The studies together looked at more than 500,000 individuals.

Introduced in the 1980s to lower the level of LDL, or 'bad,' cholesterol, statins are the best-selling drugs in the US, with more than 11 million consumers spending more than $12.5 billion each year. But the cancer prevention aspect has come somewhat as a surprise.

You could potentially have all the compounds you need generated in culture in your lab. Eric Schmidt, University of Utah

“When the drugs were developed, there was some evidence that high doses caused liver cancer in rodents, so studies were done to determine whether they were carcinogenic,” says Jim Dimitroulakos, senior scientist at the Centre for Cancer Therapeutics at the Ottawa Hospital Research Institute.

Instead, most evidence seems to indicate that the drugs reduce cancer risk. The most recent results build on previous epidemiological studies and show that people taking statins can cut their risk of pancreatic cancer by 59%, prostate cancer by 50% and colorectal cancer by 49% (N. Engl. J. Med. 352, 2182–2192; 2005). Some studies show that in comparison with other classes of cholesterol-lowering drugs, such as fibrins and bile acid–binding resins, statins may be superior in lowering cancer risk (Arch. Int. Med. 160, 2363–2368; 2000).

Evidence of statins' preventive power is mounting particularly with breast cancer. In a study of 2,000 women in Seattle, those taking statins for five years on average had a 30% lower risk of breast cancer (Cancer 100, 2308–2316; 2004). Lead investigator Denise Boudreau is conducting a prospective study of 84,000 women to examine the link between statins and cancers of the breast, prostate and reproductive organs over 14 years; results are expected in 2006. Data from analysis of statin use among 150,000 women in the Women's Health Initiative are expected later this year.

Statins' effect on cancer risk is plausible because the drugs inhibit many molecules necessary for crucial functions such as membrane integrity, cell signaling, protein synthesis and cell cycle progression, says Boudreau. For instance, cerivastatin has been shown to inhibit signaling pathways associated with metastasis in a breast cancer cell line and lovastatin inhibits mammary tumor formation and metastasis in mice (Carcinogenesis 22, 1139–1148; 2001; Breast Cancer Res. Treat. 50, 83–93; 1998). In cancer cells, statins have been shown to arrest growth, prevent invasion of distant sites, sensitize cells to the damaging effects of radiation and trigger cell death. Statins' effect might also be linked to cholesterol production in hormone-sensitive cancers, some researchers suggest.

If further studies confirm these results, the public health implications are significant. But randomized placebo-controlled studies must first clarify the exact nature of the effect, says Boudreau. “We also need to understand more about the risks associated with long-term use of statins.”