Why Irish women stop using cancer ‘wonder drug’ Tamoxifen

Figures show about one Irish woman in five stops taking Tamoxifen or aromatase inhibitors within five years


Breast cancer prevention drugs are regarded by many as a “wonder drug” to increase the survival rates for those diagnosed with the most common cancer for women in Ireland. However, figures show about one Irish woman in five stops taking the endocrine therapy, which is normally Tamoxifen or aromatase inhibitors (AI), within five years.

Dr Cathy Kelly, a consultant medical oncologist from the Mater Misericordiae University Hospital in Dublin, says 70-75 per cent of women who are treated for breast cancer every year are prescribed the drugs.

The latest statistics from the National Cancer Registry Ireland show about 2,800 women are diagnosed annually, higher than the EU average. While survival rates continue to increase, on average 690 Irish women die each year from breast cancer. This puts Irish mortality rates third-highest in the EU.

Kelly, who has worked in oncology for almost 15 years, says Tamoxifen is suitable for patients with oestrogen receptor-positive breast cancer to try to prevent it from coming back.

“It reduces the risk of dying of cancer by one-third. Tamoxifen can be given to women of all ages, it has huge benefits and the tablets are cheap. It has been used in Ireland over three decades. We have worldwide proof it has improved survival,” she says.“It’s as important as chemotherapy and, in some cases, more important.”

Kelly, who is chairwoman of Clinical Trials Ireland, says it is normally recommended to take the drug for five years, but recent studies have shown 10 years could be beneficial.

She says the number of women who stop taking the drug after one year is high.

“That’s a massive cause of concern for medical oncologists,” says Kelly.

“As a medical oncologist, really the most important type of recurrence we want to prevent is what we call a distant recurrence, that’s outside of the breast in areas such as the brain, bone, liver and in the lungs.”

The figure of one in five women stopping taking Tamoxifen or aromatase inhibitors in five years are based on soon to be published RCSI research linking National Cancer Registry Ireland figures to pharmacy claims data from Ireland’s Primary Care Reimbursement Services (PCRS). It involved data on 3,415 women who received treatment from 2000-2012.

Side effects

It begs the question about side effects of the drugs. Kelly says common side effects from Tamoxifen include hot flushes and night sweats. “Often women taking it think it can make them post menopausal but it doesn’t. It can give some post menopausal symptoms but it doesn’t affect their fertility,” she says.

Weight gain and blood clots are other concerns. “We have excellent data from large randomised trials to show it doesn’t cause weight gain,” she says. “For people overly concerned of the risk of a clot, that risk is the same as a woman on an oral contraceptive pill and HRT. It’s an extremely small risk.”

Kelly says more serious side effects such as endometrial cancer are “very rare” but normally can be treated. “Cataracts can happen after a number of years but they’re not life threatening and can be easily treated. Bone pain can be treated if it is related to the drug,” she says.

In response to the number of women who stopped taking the drugs, a study funded by the Health Research Board was carried out to explore what influenced the rate of nonadherence to the medication.

Senior researcher Caitriona Cahir, from the Royal College of Surgeons and Trinity College Dublin, was one of the authors of the journal recently published on the medication habits of women in Ireland.

“We were surprised [at the 20 per cent figure]. There’s a perception because it’s breast cancer, women will take their treatment medication but it’s a difficult medication to take and there are side effects. It’s also a long commitment,” she says about the study that involved interviewing 31 women. “The results showed medication-taking habits were based a lot around a personal belief system.”

Study groups

Three groups of women were questioned – those who took the tablet daily, women who had stopped taking it completely and those who did not take it consistently.

“We wanted to compare the three groups. The answers showed women gave their choice an awful lot of thought. There are very valid reasons why women decide to take it and why they don’t.”

Cahir says women who had stopped taking their hormonal therapy did not believe in the “necessity” of the medication. “Many believed in enjoying their time they have now rather than focusing on breast cancer recurrence,” she says.

“It was a big decision for them to stop taking it; a very real and logical one. It’s not something they do on a whim. Some had a general distrust of medication. They’ve had a lot of treatment and had enough.”

Other women who had stopped their medication said it was because of the side effects including hot flushes, severe sweating, headaches and bone pain, she says.

“Some were not prepared to tolerate the side effects. Bone pain can be very debilitating.”

Cahir says the women who took the drugs daily explained they believed very strongly in their therapy.

“A term they used was ‘lifeline’. They believed the benefits would far outweigh any side effects. They believe any side effect is better than getting cancer again,” she says.

“You have very different people with very different opinions. Both are very valid. Women skipping doses, they definitely perceived a need for this treatment but were also a bit like the women who had a general distrust of medication and had anxiety over taking it.”

Cahir says the study the team is currently working on is to identify the best support system needed for women on the drugs.

“Tamoxifen and hormone therapy can be a difficult drug to take,” she says.

“The next step we are working on is identifying what exactly can be done to support women prescribed hormonal therapy and how we can develop survivorship care in clinical practice.”