Every year, breast cancer kills thousands of women. A new study from the U.K. shows that breast cancer patients can reduce risk of its recurrence and prevent death by the cancer if they took tamoxifen for the prescribed five-year period.

Tamoxifen is used to treat breast cancer that has already spread to other parts of the body. The drug belongs to a class of drugs called as antiestrogens and works by blocking the activity of the female hormone, estrogen.

But the drug has significant Side-effects. They include vision problems, loss of appetite, fever, rash, blisters and muscle weakness. The drug can also increase risk of other cancers such as those of liver and uterus.

The study conducted by researchers at University of Glasgow and funded by The Breast Cancer Campaign found that about 400 lives could be saved each year if women complete the entire treatment.

Researchers looked at data of 1263 women to assess their adherence to the treatment. They found that women with low treatment adherence- those that filled less than 80 percent of the prescription- had high risk of dying due to breast cancer. These women also had higher medical costs and lower quality of life post treatment.

"Tamoxifen is one of the most effective treatments for breast cancer when taken as prescribed but sadly some women find it intolerable to take the full five year course and risk recurrence of their disease," Baroness Delyth Morgan, Chief Executive of Breast Cancer Campaign said  in a news release. "This study is a timely reminder that it's so important that women are given support to continue taking their tamoxifen so that they have the best possible chance to outlive breast cancer."

The study was published in the British Journal of Cancer.                              

Breast cancer is one of the most common cancers diagnosed in women in the U.S. Despite its high prevalence, researchers aren't sure why normal breast cells turn cancerous. According to most experts, breast cancer is caused by a combination of genetic, hormonal and environmental factors. According to estimates by the National Cancer Institute, 232,340 new cases of female breast cancer will be diagnosed in 2013 in the U.S and nearly 40,000 women will die due to breast cancer.