Switching Drugs Improves Breast Cancer Survival Rates, Long-Term Trial Data Shows
31 October 2011 - Patients have a better chance of surviving breast cancer if they switch drugs half way through their five-year treatment, according to a study jointly led by the ICR.
Until recently, most women diagnosed with early stage oestrogen receptor-positive (ER+ or hormone sensitive) breast cancer were given tamoxifen for around five years after surgery to help prevent the disease coming back. This therapy was once viewed as the ‘gold-standard’ treatment, however increasing numbers of women are now treated with aromatase inhibitors either as first-line treatment or after treatment with tamoxifen.
A large-scale trial called the Intergroup Exemestane Study (IES) was set up across 37 countries in 1998 to examine the long-term effectiveness of switching to exemestane after two to three years tamoxifen to complete a total of five years adjuvant treatment.
Results published in 2007 showed that women who switched drugs had higher survival rates, however it was unclear whether this effect would continue in the years after treatment finished and whether there would be any long-term side-effects.
The new analysis included 4,052 patients with ER+ cancer and 547 women with tumours whose ER status is unknown. After a median follow-up of 91 months, women who had been switched to exemestane were 18 per cent less likely to have disease recurrence and were 14 per cent less likely to have died than those who stayed on tamoxifen.
Lead author Professor Judith Bliss, Director of the ICR’s Clinical Trials & Statistics Unit (CTSU), says: “The long-term results from our study show that the improvements observed following the switch to exemestane are real and continue for at least five years after finishing treatment.”