Herceptin added to hormonal therapy increases progression-free survival in patients with advanced HER2-positive breast cancer

Data presented for the first time today at the European Society for Medical Oncology (ESMO) meeting shows that the addition of Herceptin (trastuzumab) to the hormonal therapy, anastrozole, keeps cancer under control for a significantly longer duration than hormonal therapy alone in patients whose advanced breast cancer is hormone receptor-positive, as well as HER2-positive.

Hormone receptor-positive breast cancer affects two-thirds¹ of patients with breast cancer and is typically considered ‘lower-risk’ due to successful treatment with hormonal therapies. However, up to a quarter of these breast cancers are also HER2-positive,² an aggressive form of the disease that requires special and immediate attention because the tumours are fast-growing and there is a higher likelihood of relapse. This is the first randomised study to show that this specific subset of ‘co-positive’ patients (both hormone receptor and HER2-positive) is actually ‘higher-risk’ or worse off, making these positive results highly meaningful.The phase III study evaluated Herceptin in combination with the hormonal therapy anastrozole versus anastrozole alone as first-line therapy (or second-line hormonal therapy) in postmenopausal women with advanced (metastatic), HER2-positive and hormone receptor-positive (ER-positive and/or PR-positive) breast cancer. Median progression-free survival, the primary endpoint of the trial, was 4.8 months for patients who received the combination compared to 2.4 months for patients who received hormonal therapy alone (p = 0.0016). Patients in the combination arm also responded significantly better to treatment (overall response rate was 20.3% versus 6.8%; p = 0.018). There was also a positive trend in median overall survival (28.5 months versus 23.9 months; p = 0.325); this is despite the fact that in the hormonal therapy alone arm, more than half of patients (58/104) crossed over to receive Herceptin during the trial when their disease had progressed, and an additional 15 patients received Herceptin at a later time point. To date, over 3,000 patients with HER2-positive breast cancer have been treated with Herceptin in Australia. Herceptin consistently benefits patients regardless of whether it is given in the early stage or advanced settings, or whether it is in combination with chemotherapy, hormonal therapy, or as a single agent. Roche is now working to prepare a submission of these results to regulatory authorities in the latter half of 2006. About the studyThe TAnDEM study, conducted by Roche, is a randomised, phase III trial. Enrolment to the trial began in 2001, and 208 HER2 and hormone receptor co-positive patients were randomized at 77 centres in 22 countries across the world. Anastrozole was scheduled at a dose of 1 mg daily until progression. Herceptin was administered in 2 mg/kg weekly doses (after an initial loading dose of 4 mg/kg) until disease progression.Overall safety data in both arms of the trial were acceptable given the known safety profile of each of the drugs in the advanced breast cancer setting. Patients in this study will continue to be followed for any side-effects.About breast cancer and HerceptinEight to nine percent of women will develop breast cancer during their lifetime, making it one of the most common types of cancer in women.³ Each year more than one million new cases of breast cancer are diagnosed worldwide, with a death rate of nearly 400,000 people per year. In HER2-positive breast cancer, increased quantities of the HER2 protein are present on the surface of the tumour cells. This is known as ‘HER2-positivity.’ High levels of HER2 are present in a particularly aggressive form of the disease which responds poorly to chemotherapy. Research shows that HER2-positivity affects approximately 20-30 percent of women with breast cancer. Herceptin is a humanised antibody, designed to target and block the function of HER2, a protein produced by a specific gene with cancer-causing potential. It has demonstrated efficacy in treating both early and advanced (metastatic) breast cancer. Given on its own as monotherapy as well as in combination with or following standard chemotherapy, Herceptin has been shown to improve response rates, disease-free survival and overall survival while maintaining quality of life in women with HER2-positive breast cancer.Herceptin received approval for use in the European Union for advanced (metastatic) HER2-positive breast cancer in 2000 and for early HER2-positive breast cancer in 2006. In the advanced setting, Herceptin is now approved for use as a first-line therapy in combination with paclitaxel where anthracyclines are unsuitable, as first-line therapy in combination with docetaxel, and as a single agent in third-line therapy. In the early setting, Herceptin is approved for use following standard (adjuvant) chemotherapy. Herceptin is marketed in the United States by Genentech, in Japan by Chugai and internationally by Roche. Source:

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2. F. Penault-Llorca, A. Vincent-Salomon, M. C. Mathieu, et al. On Behalf Of The Esther Study Group. Incidence and implications of HER2 and hormonal receptor overexpression in newly diagnosed metastatic breast cancer (MBC). American Society of Clinical Oncology (ASCO) Meeting Meeting Abstracts, 23: 764, 2005.
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