What is the story?
A new breast cancer drug could save the lives of more than 1,000 women a year, according to media reports.
An eight-year study has shown that postmenopausal women with early breast cancer survive for longer if they are switched from the ‘gold standard’ tamoxifen after two or three years and given exemestane (Aromasin).
Giving women tamoxifen after breast cancer surgery cut the risk of dying by 33 per cent.
Switching to exemestane for two years reduced this risk to 50 per cent. Researchers said combination may be effective because cancer cells can become resistant to tamoxifen during treatment, but exemestane kills them off.
Tamoxifen works by interfering with the production of oestrogen, which often fuels the growth of breast cancer.
Exemestane is one of a group of drugs known as aromatase inhibitors. It works by blocking oestrogen. Last year, the drug- rationing body NICE approved use of this drug on the NHS.
What is the research?
The news stories were prompted by an update of the Intergroup Exemestane Study (IES).
This phase III international trial looked at whether switching patients from tamoxifen to the steroidal aromatase inhibitor exemestane is beneficial.
It involved 4,724 postmenopausal women with unilateral invasive breast cancer that was oestrogen-receptor-positive or oestrogen-receptor-unknown.
All of the patients had taken tamoxifen as an adjuvant for two to three years without relapse.
They were randomly assigned to receive exemestane 25mg daily or continue with tamoxifen 20mg or 30mg daily for the remainder of the recommended five-year endocrine treatment period.
Early release of IES results in 2004 showed that switching to exemestane reduced the risk of recurrence. But follow-up was too short to see if the switch had any effect on overall survival.
The findings come from an analysis of outcomes an average of 4.6 years after treatment ended. This is equivalent to 10,335 women-years of post-treatment follow-up. During this time, 222 of the 2,352 women in the exemestane group died and 261 of the 2,372 in the tamoxifen group died.
Intention-to-treat analysis showed that switching to exemestane resulted in a 15 per cent relative reduction in risk of death compared with continued tamoxifen treatment.
When 122 patients with oestrogen-receptor-negative disease were excluded from the analysis, a 17 per cent relative reduction was noted.
Exemestane was also associated with a 3.5 per cent absolute improvement in disease-free survival five years after randomisation.
What do the researchers say?
Lead researcher Professor Charles Coombes, an expert in cancer medicine at Imperial College London and Hammersmith Hospital, said: ‘The results show that if you just keep people on tamoxifen for five years, then obviously you get a benefit. But if you switch to an aromatase inhibitor after three years you get a better outcome and fewer side effects.’
Tamoxifen is known to increase the risk of DVT and endometrial cancer.
‘It appears that some cancer cells escape the effects of tamoxifen and we know that aromatase inhibitors are effective in patients who relapse while on tamoxifen,’ said Professor Coombes.
Although the latest research focused on exemestane, Professor Coombes said all aromatase inhibitors have the same effect.
‘Increasingly these patients are being referred back to GPs because specialists are flat out,’ he said. ‘If patients have been on tamoxifen for more than two years, GPs should question whether they should switch to one of the aromatase inhibitors.’
Research has shown that providing bone mineral density is normal when treatment is initiated, aromatase inhibitors do not have detrimental effects for bone health, as was feared.
What do other experts say?
Professor John Toy, medical director at Cancer Research UK, said: ‘These results suggest that a sequence of tamoxifen and exemestane could help reduce breast cancer deaths, and we will follow these results to see how women fare in the long-term.
What the papers said
“New cancer drug to save a thousand lives a year”
“The breast cancer breakthrough saving 1,000 women a year”
“Drug will save lives of 1,000 women every year”