'Antidepressant could hamper breast cancer recovery'
THOUSANDS of women battling breast cancer are being warned that taking a popular antidepressant could slash their chance of survival.
A new study has found that the antidepressant Seroxat can interfere with a key breast cancer drug.
Women who were being given tamoxifen to fight breast tumours were less likely to survive if they also took the antidepressant.
The researchers said their results had "major implications for clinical practice" and warned women on Seroxat to go and see their GP.
Around 44,000 women a year are diagnosed with breast cancer and of these, one in four are likely to suffer depression.
One of the most common drugs to treat breast cancer is tamoxifen, which is taken by thousands of breast cancer patients every year.
But tamoxifen has side-effects, including causing hot flashes.
This has led many GPs to prescribe Seroxat to women to reduce the hot flushes and alleviate depression.
Now a study published in the British Medical Journal suggests this form of anti-depressant interferes with tamoxifen and that women should switch to other brands.
The research by a team from the University of Toronto in Canada looked at 2,430 women aged over 66 who were treated between 1993 and 2005.
All the women were taking tamoxifen and one of five anti-depressants known as selective serotonin reuptake inhibitors (SSRIs), including paroxetine, better known as Seroxat, which was the most commonly prescribed drug.
Over a typical follow-up of 2.4 years, 374 women died from breast cancer.
Analysis of health records showed women taking paroxetine were far more likely to die from breast cancer and were slightly more likely to die from any other cause when compared with women not on paroxetine.
The researchers, who believe paroxetine interferes with the metabolism of tamoxifen, found no evidence that other SSRIs increased the risk of death.
They concluded: "We estimate that use of paroxetine for 41 per cent of tamoxifen treatment (the median overlap in our sample) would result in one additional breast cancer death within five years of cessation of tamoxifen for every 19.7 patients so treated; the risk with more extensive overlap would be greater.
"In conclusion, our findings indicate that the choice of antidepressant can significantly affect survival in women receiving tamoxifen for breast cancer."
The authors stressed that women should not stop taking tamoxifen and said their study does not imply that paroxetine itself causes or influences the course of breast cancer.
"This is simply a situation in which paroxetine impairs the effectiveness of tamoxifen," they wrote.
Dr David Juurlink, one of the study's authors, added: "These results highlight a drug interaction that is extremely common, widely under-appreciated and potentially life-threatening, yet uniformly avoidable.
"Tamoxifen is a crucial element of therapy for patients with hormone receptor-positive breast cancer regardless of age or breast cancer stage.
"When co-prescription of tamoxifen with an antidepressant is necessary, preference should be given to antidepressants that exhibit little or no impact on tamoxifen's metabolism."
Last night, breast cancer charities said women should not stop taking tamoxifen. Instead they should go and see their GP to discuss switching to another antidepressant.
Meg McArthur, from Breakthrough Breast Cancer, said: “This research is welcome because it gives an insight into how the effectiveness of tamoxifen could be influenced by taking antidepressants.
Tamoxifen remains a beneficial treatment for breast cancer and as several antidepressants are available doctors should be able to find the right combination for patients.
“This should not put patients off taking tamoxifen and any concerns should be discussed with their doctor.”