Anti-cancer drug risk

Tamoxifen is prescribed in the early stages of breast cancer

Women who take the anti-cancer drug tamoxifen are more likely to die from uterine cancer than those who are not receiving the medication, according to a study.

Research carried out in The Netherlands has suggested that women who are prescribed tamoxifen are up to seven times more likely to develop uterine or endometrial cancer.

Previous studies have linked tamoxifen, which is used to treat women with a history of breast cancer, with other cancers.

However, the Dutch study is the first to show an increased risk of dying from cancer of the uterus.

Tamoxifen is prescribed to women who have had a cancerous tumour removed from a breast. It can also be given to those at risk of developing breast cancer or those with a family history of the disease.

Long-term tamoxifen users are more likely to die from endometrial cancer than are non-users

Flora van Leeuwen, Netherlands Cancer Institute

First developed in the UK, the drug is relatively cheap and helps prevent the cancer coming back after the initial surgery to remove a breast tumour. It is usually prescribed for five years.

But the Dutch research has found that the longer a women is on the treatment the greater her risks of developing tumours in the lining of the womb.

Doctors at the Netherlands Cancer Institute in Amsterdam report that their study found that women who took tamoxifen for between two and five years were twice as likely to develop uterine cancer than those who had not received the drug.

But women who had taken the drug for more than five years were seven times more likely to develop the condition than non-users.

Previous studies have identified a link between tamoxifen and cancer of the uterus.

However, the Dutch study suggests that this form of cancer among women who take the drug is at a very advanced stage when it is discovered. This means they are more likely to die from the disease.

Flora van Leeuwen, one of the researchers, said: "Contrary to current opinion, long-term tamoxifen users are more likely to die from endometrial cancer than are non-users."

'No treatment consequences'

The authors of the study added that they do not believe their findings should change the way breast cancer in women is treated.

"We do not think that this unexposed result has consequences for the treatment of breast-cancer patients because the survival benefits of tamoxifen for breast cancer far outweigh the adverse effects," they noted.

Writing in the latest issue of the medical journal The Lancet, they added that doctors should think twice about using the drug.

"Our finding of a less favourable prognosis of endometrial cancer after long-term tamoxifen use suggests the need to question widespread use of the drug as a preventative agent in healthy women at increased risk of breast cancer," they said.

Karen Gelmon, from the British Columbia Cancer Agency in Canada, writing in the same journal, said: "Tamoxifen remains a remarkable drug with proven benefit."

But she added: "Before bounding forward with prescriptions for tamoxifen, clinicians should remembers its risks and benefits."

Endometrial cancer is still extremely rare in women taking tamoxifen

Professor Professor Jack Cuzick, Imperial Cancer Research Fund

Delyth Morgan, chief executive, Breakthrough Breast Cancer, said: "The benefits of tamoxifen are well known. In the treatment of breast cancer these outweigh the risks.

"As with any drug, there are risks as well as benefits. The patient must be informed of these and be involved in the decision-making process.

"We must see more investment in cancer research, so that better treatments are developed and made available to patients."

Professor Jack Cuzick, head of epidemiology at the Imperial Cancer Research Fund, said the study highlighted the need for long-term follow-up of women taking tamoxifen.

"Endometrial cancer is still extremely rare in women taking tamoxifen - the women taking part in the trial are 10 times more likely to develop breast cancer than endometrial cancer, so the benefits appear to strongly outweigh the risks at this stage."