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Breast cancer: success of additional therapy with zoledronic acid confirmed in follow-up

(Chicago/Vienna, 06th June 2011) The additional prescription of a bisphosphonate – zoledronic acid – which was originally used to compensate therapy-induced osteoporosis in patients with breast cancer does more than just prevent relapses. It has been found to increase with statistical significance the survival rate of women taking the drug. The long-term study results, published after 76 months, were presented by Michael Gnant at the leading American Society of Clinical Oncology Conference (ASCO/Chicago).

“For the first time, we have been able to extract data from the study revealing information about the patients’ total survival rates”, explained Michael Gnant. The presentation featured results of a more than six-year follow-up of breast cancer patients who had been previously enrolled in the ABCSG-12 trial.

The study cohort involved 1,803 women who were suffering from stage I or II – i.e. a relatively early stage – of hormone-dependent breast cancer. They all fell ill before the onset of the menopause. Since their tumour depended on growth stimulus from their bodies’ own oestrogen, the patients were given treatment following surgery that artificially put them into the menopause.

They also received additional anti-hormonal therapy with tamoxifen or anastrozole. In view of the bone decay associated with this treatment (osteoporosis), half of the patients (around 900) ultimately received a bisphosphonate every six months (zoledronic acid).

Three years ago – at the 2008 ASCO Congress – the Austrian scientists caused an international stir. They were able to demonstrate that the patients who had been given the osteoporosis drug were not only protected from bone decay, but also exhibited significantly fewer relapses in their breast cancer. It is assumed that the bisphosphonates, as well as strengthening the bones and preventing bony metastases, also have an anti-tumour effect of its own.

Now, after 76 months of follow-up, a statistically significant survival advantage has also been seen in patients who were given the bisphosphonate: the overall mortality rate (not just due to cancer) fell by 41 per cent. The advantage came from a particularly powerful effect of the osteoporosis drug in patients with breast cancer who were aged over 40. In this age group, the overall mortality rate fell by as much as 49 per cent. Gnant: “This means that, with three years of treatment, we are achieving a long-term effect and ultimately achieving a real increase in the cure rate."

The results of the study following an observation period of 62 months have been published in the current edition of Lancet Oncology:

» Adjuvant endocrine therapy plus zoledronic acid in premenopausal women with early-stage breast cancer: 62-month follow-up from the ABCSG-12 randomised trial
Michael Gnant, Brigitte Mlineritsch, Herbert Stoeger, Gero Luschin-Ebengreuth, Dietmar Heck, Christian Menzel, Raimund Jakesz, Michael Seifert, Michael Hubalek, Gunda Pristauz, Thomas Bauernhofer, Holger Eidtmann, Wolfgang Eiermann, Guenther Steger, Werner Kwasny, Peter Dubsky, Gerhard Hochreiner, Ernst-Pius Forsthuber, Christian Fesl, Richard Greil;
The Lancet Oncology, Early Online Publication, 4 June 2011; doi:10.1016/S1470-2045(11)70122-X