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Published: Tuesday, March 22, 2011 - 17:27

Newly published research findings reiterates the superior benefit of the recommended 5 year course of Tamoxifen for breast cancer when compared to a 2 year course. In addition, there appears to be protection against cardiovascular (CV) disease as well.

The cancer protection and heart-disease risk reduction were noted 15 years after starting treatment, according to the study published online March 21, 2011 in the Journal of Clinical Oncology.

The findings may surprise many women on the medication, said Allan Hackshaw, deputy director of Cancer Research and the University College London Cancer Trials Centre. "I think many women don't realize the benefits last a long time if they can complete the five-year course, and particularly also the cardiovascular disease benefit," he said.

Hackshaw and his colleagues studied follow-up data for 3,449 participants in the Cancer Research UK "Over 50s" trial which compared Tamoxifen use of five years and two years by women with early breast cancer. The women were between 50 and 81 years of age at the start.

During the initial study period, 1987 to 1997, the women took 20 milligrams of Tamoxifen a day for two years. After that, they were assigned randomly to stop taking the drug or to continue taking Tamoxifen for three more years, if they were recurrence-free.

The researchers then tracked cancer recurrences, new tumours, death and cardiovascular events through April 2010.

There were 1,103 recurrences, 755 deaths from breast cancer, 621 cardiovascular events and 236 deaths from cardiovascular events. They found that 15 years after the women first began taking Tamoxifen, for every 100 who took it for five years, nearly six fewer women suffered a recurrence compared to those on the two-year regimen.

The longer treatment reduced the risk of breast cancer developing in the opposite breast by 30 percent, the researchers found.

59% reduction in cardiovascular deaths

The effect on heart disease among women 50 to 59 years old was even stronger -- a 35 percent reduction in cardiovascular events and a 59 percent reduction in deaths from cardiovascular problems.

However, among older women the heart effect was much smaller and not statistically significant.

The majority of breast cancers are estrogen-receptor positive. Tamoxifen, which has been in use for over 30 years to treat breast cancer, inhibits the ability of estrogen-receptor positive cancers to grow by disrupting estrogen activity.

It's not clear how the drug protects against heart disease, Hackshaw said. "But there is evidence that Tamoxifen reduces lipid levels which we know, in turn, reduces cardiovascular risk," he explained.

It's possible that the protective effect declined in older women because damage to the arteries had already occurred, he speculated.

The new research is a timely reminder about the benefits of Tamoxifen, said Dr. Joanne Mortimer, vice chair of medical oncology at the City of Hope Comprehensive Cancer Center, Duarte, Calif., and director of its women's cancers program.

Aromatase inhibitors

Aromatase inhibitors are a different class of drugs used in breast cancer. They work by suppressing the production of estrogen hormone. Although many doctors prescribe medications known as aromatase inhibitors for breast cancer instead of Tamoxifen, Mortimer said Tamoxifen is still widely prescribed.

"Maybe for those who have problems with an aromatase inhibitor, they would be comforted by the fact that Tamoxifen is an alternative and has a favourable effect on normal tissues, like bone and heart muscles," Mortimer said.

While not discounting the effectiveness of aromatase inhibitors, Hackshaw said Tamoxifen is much less expensive.

Expensive drugs

In those places in the  world where the state does not foot the bill, aromatase inhibitors can be prohibitively expensive. A month's supply of 20-milligram tablets, the dose used in this study, is about $100. Brand-name versions of aromatase inhibitors can cost more than $500 for 30 pills, although cheaper generic versions are also available.

In an editorial accompanying the study, Dr. Kathleen Pritchard, of Sunnybrook Odette Cancer Center in Toronto, said the findings about heart protection should be regarded with ''some caution,'' although the finding is of interest.

Some research has found cardiovascular deaths higher in women on aromatase inhibitors than Tamoxifen, she writes, although not all studies of Tamoxifen have found the cardiovascular protection. So, still more research is needed, she said.


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Breast and heart protective effects of Tamoxifen 5-year course reiterated

By Dr Joe Kabyemela, MD