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New breast cancer drugs: who can benefit?
NICE, the government drugs watchdog, has now given final approval to a new generation of breast cancer drugs that have been hailed as a breakthrough in the treatment of postmenopausal women
Studies have shown that the three drugs, collectively known as aromatase inhibitors, increase life expectancy dramatically for many of those with early breast cancer and have fewer side effects than tamoxifen, the old gold standard treatment.
It's believed that more than 31,000 of the 42,000 women diagnosed with the disease every year will benefit now that the National Institute for Health and Clinical Excellence has given final approval for doctors to prescribe the drugs in England and Wales. They have already been granted approval for use in the NHS in Scotland.
Thousands of women currently receiving tamoxifen are also expected to switch to one of the new drugs, either immediately or in several years' time.
According to Professor Trevor Powles, Emeritus Professor of Breast Oncology at the Institute of Cancer Research, the new class of drugs marks a watershed in breast cancer treatment.
"There's no doubt that these drugs are very important indeed," says Prof Powles, who is also a patron of the charity Breast Cancer Care. "They are very effective and don't have the serious side effects associated with tamoxifen, such as endometrial cancer, blood clots and uterine problems.
"Aromatase inhibitors were previously used for patients with breast cancer who had relapsed, but trials were then done giving them to patients who had primary breast cancer, with very good results.
"They are all pretty much interchangeable in terms of biology, but the trials were all carried out under different circumstances."
How they work
The new AI drugs are Arimidex (sometimes referred to by its generic name, anastrozole), Aromasin (exemestane) and Femara (letrozole). They work by blocking the production of oestrogen in the body, the hormone responsible for the growth and recurrence of many breast cancers.
Oestrogen is produced in the ovaries and in the adrenal glands, situated just above the kidneys, using a substance called aromatase. Aromatase inhibitors don't block oestrogen production by the ovaries, but they do prevent other tissues from making it.
This is why they are ideal for postmenopausal women, whose ovaries are no longer producing oestrogen. For pre-menopausal women, tamoxifen will still be the standard treatment.
Tamoxifen blocks a tumour's ability to bind itself to oestrogen, AIs work by reducing the levels of oestrogen in the body, which can lead to slightly increased risk of bone -thinning and fractures associated with osteoporosis. But while the three new drugs are similar in principle, they have been licensed for different purposes.
Making the switch
Arimidex has been licensed to be used as an alternative to tamoxifen, which is prescribed for five years to women who have undergone surgery and possibly chemo- and radiotherapy. Women would receive Arimidex instead for the same period. Clinical studies compared use of Arimidex with tamoxifen in more than 6,000 postmenopausal women with breast cancer and showed that it cuts the chances of breast cancer an extra 26 per cent over and above the 50 per cent reduction provided by tamoxifen.
For women already taking tamoxifen, their medication can be switched to Aromasin after two to three years. A study co-ordinated by Cancer Research UK revealed that patients who switched from tamoxifen to Aromasin halfway through their five-year treatment reduced the risk of the disease returning by a third.
Femara has been licensed for use with early breast cancer and can be used to shrink a tumour before surgery. It now has have approval for use after five years' tamoxifen treatment. The results of a clinical trial revealed that women who took Femara after taking Tamoxifen for five years lowered their risk of recurrence by 43 per cent, compared to women who took a placebo after taking tamoxifen for five years.
The role of tamoxifen
"There is a debate about whether these drugs should used instead of tamoxifen or after tamoxifen," says Prof Powles. "Many us feel that tamoxifen as the primary treatment, followed by an aromatase inhibitor might be better than using one of the new drugs instead of tamoxifen."
Suggestions that tamoxifen could be phased out completely in favour of the new drugs, is wide of the mark. Nor should women already on tamoxifen feel they are missing out if their doctor doesn't switch them over to an AI straight away.
"I think that if someone is on tamoxifen and it's not causing any problems then there's a very good argument for leaving it two to three years before a switch," he says. "There may be reasons to suppose that if you use tamoxifen first, then the AIs work better after tamoxifen rather than using them instead."
Tamoxifen has been credited with helping more than 20,000 women survive breast cancer, since its launch in the 1980s. There is a great body of data about tamoxifen, but little is known about the long term benefits and drawbacks of these new drugs, about which there is much less information.
So far the five-year data hasn't indicated any major health repercussions, but increased risk of bone fracture has been established. There may be other problems that emerge after AIs have been used for five years, however. For example the effect they may have on the heart or brain is as yet unknown; low levels of oestrogen can affect cognitive function.
But patients will benefit if their oncologists have the choice of prescribing either an AI or tamoxifen, according to Prof Powles. In individual cases an aromatase inhibitor may be more appropriate line of treatment.
"The choice of giving an aromatase inhibitor is useful if you don't want to give tamoxifen because of the risk of blood clotting or if the patient is having lots of hot flushes and night sweats, because tamoxifen makes them worse, but aromatase inhibitors don't have as marked an effect," says Prof Powles.
The cost factor
The new drugs are much more expensive than tamoxifen; a course of any one will cost about £900 a year, compared to £70 for tamoxifen. But there will be savings to the NHS as AIs have fewer side effects that can be expensive to treat.
Now that NICE approval has been finalised, many women with breast cancer will be anxious to know whether an aromatase inhibitor might be the best treatment for them, but Prof Powles urges caution.
"The situation is not as simple as it might seem initially," he says. "Women should be aware that there's a huge amount of marketing going on by major companies to get their products out front first.
"Patients should consult with their doctors about the best option for them."
Written by Judith Woods
Reader comments
Being on Tomoxofin for the first 12 months after a mastectomy caused thickening of the lining of the womb and large fibroids requiring a D & C type operation hospital stay duration of two days. Doctor then put me on Arimadex tablets which have caused no problems at all in the last 20 months.
Posted by: Greta Aaron | 30/01/2008 12:32:27
Information on this site is for interest only and is not a substitute for professional medical advice. You should consult your own doctor about any specific health concerns.
