Tamoxifen Can Halve Breast Cancer Risk When Prescribed Longer
June 3, 2013

Tamoxifen Can Halve Breast Cancer Risk When Prescribed Longer

Lee Rannals for redOrbit.com — Your Universe Online

Researchers announced new findings that taking one breast cancer drug for twice the time suggested can substantially increase survival rates.

The scientists said that women diagnosed with breast cancer who take tamoxifen for 10 years, rather than five years, halve their chances of dying.

"These findings are extremely exciting for women who are diagnosed with the most common type of breast cancer," said Dr Julia Wilson, Director of Research at Breakthrough Breast Cancer. "The study proved that 10 years of taking tamoxifen has a much higher survival rate than the current five years, which is vital in helping us to stop breast cancer coming back and, more importantly, to help us stop women dying from breast cancer."

The Cancer Research UK study looked at 7,000 women with breast cancer who either continued taking the drug for another five years or stopped treatment. They found that the women who took tamoxifen for 10 years, 25 percent had less recurrence of breast cancer while 23 percent fewer died compared to women who took the drug for just five years.

“These results are important as they establish that giving tamoxifen for longer than the current standard of five years significantly cuts the risk of breast cancer returning," said Dr. Daniel Rea, clinical lead researcher based at the University of Birmingham. “Doctors are now likely to recommend continuing tamoxifen for an extra five years and this will result in many fewer breast cancer recurrences and breast cancer deaths worldwide. Tamoxifen is cheap and widely available so this could have an immediate impact.”

The researchers said about 75 percent of breast cancers are oestrogen receptor positive and may benefit from hormone therapy. Tamoxifen blocks these receptors, helping to reduce the chances of the cancer returning after surgery or developing in the other breast. Wilson said the well-established drug means the guidelines for usage should be easy to amend, making it easy for doctors to start employing it on patients.

"We do however encourage all women taking this treatment to speak to their doctor about their individual circumstances as there can be side effects involved," Wilson said.

The doctors warn that women taking the drug can experience side effects similar to menopausal symptoms, like night sweats and hot flashes. Moreover, very rare, serious side-effects can occur as well, such as increased risk of endometrial cancer, blood clots, and stroke. The researchers estimate that for every endometrial cancer death that occurs as a side effect of long-term tamoxifen, there would be 30 deaths from breast cancer prevented.

“Five years of tamoxifen is already an excellent treatment but there have been concerns that giving it for longer might not produce extra benefits and could even be harmful. The aTTom study establishes that the benefits of taking tamoxifen for longer greatly outweigh the risks," said Prof. Richard Gray, based at the University of Oxford and presenting the aTTom results at ASCO.