08 August 2013
A combination of two hormone therapy drugs does not provide significant clinical benefit over single-drug treatments, according to the latest trial led by researchers from The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust.
The SoFEA trial compared three different hormone therapy drug regimes: fulvestrant with anastrozole, fulvestrant alone and exemestane. They were given to post-menopausal women with oestrogen receptor positive (ER+) breast cancers which had become resistant to other treatments called non-steroidal aromatase inhibitors (NSAIs). The best way to treat these patients is unclear, so the trial aimed to see if a combination of drugs might be the answer.
Aromatase inhibitors reduce oestrogen levels in the body, and ER+ tumours rely on oestrogen to grow. When tumours become resistant to NSAIs, current clinical practice is to give exemestane, a powerful steroidal aromatase inhibitor. Laboratory studies had previously suggested that combining another oestrogen-blocking drug called fulvestrant with the aromatase inhibitor anastrozole could further reduce oestrogen levels. However, results from the SoFEA trial showed that the fulvestrant-anastrozole combination doesn’t translate into additional significant clinical benefits for patients.
Corresponding author and Chief Investigator of SoFEA Prof Stephen Johnston of the Royal Marsden NHS Foundation Trust, said: “Blood samples from this trial showed that our findings were not due to the failure of anastrozole to lower oestrogen levels. Instead it is likely that alternative signalling pathways which bypass oestrogen, the original driver of the cancer, are being used to enable the breast cancer to continue to grow.”
Professor Judith Bliss, co-author and Director of the ICR Clinical Trials and Statistics Unit, confirmed: “SoFEA has shown that following loss of response to NSAIs in postmenopausal women with hormone-receptor positive advanced breast cancer, maximum double hormone therapy using 250mg fulvestrant combined with oestrogen deprivation is no better than either fulvestrant or exemestane alone”.
The results of this trial are published in The Lancet Oncology.