The results from a pooled analysis of two Phase III Halaven(R) (eribulin) trials are published in Breast Cancer Research and Treatment. Findings from the pooled analysis show that eribulin improves overall survival in women compared to control. This overall survival benefit was observed in women with human epidermal growth-factor receptor-2 (HER2) negative breast cancer and triple negative breast cancer (TNBC).[1]
"These pooled data show the overall survival benefit of eribulin in the important and often forgotten about HER2 negative and triple negative subtypes, who constitute the majority of patients with cancer. Chemotherapy remains the backbone of treatment for women with metastatic breast cancer and this analysis confirms that these women benefit from eribulin," comments Dr Chris Twelves, Professor of Clinical Cancer Pharmacology and Oncology, and Honorary Consultant in Medical Oncology at the University of Leeds and St James's Institute of Oncology.
The pooled analysis examined data from two pivotal Phase III studies in 1,864 women; EMBRACE (Eisai Metastatic Breast Cancer Study Assessing Treatment of Physician's Choice Versus Eribulin)[2] and Study 301.[3] The objective of the analysis, initially requested by the European Medicines Agency (EMA), was to assess overall survival in the overall intent to treat (ITT) population and in specific patient subgroups, previously treated with an anthracycline and a taxane, based on HER2 and hormone receptor status.
In the pooled analysis, eribulin was found to improve significantly overall survival vs. control in the ITT population (15.2 vs 12.8 months, HR=0.85 [95% CI, 0.77, 0.95]; p=0.003). A significant overall survival benefit was observed in women with HER2 negative breast cancer (15.2 vs 12.3 months, HR=0.82 [95% CI, 0.72, 0.93]; p=0.002), a subtype that affects an estimated 85% of women with breast cancer.[1],[4],[5] This overall survival benefit was also seen in people with TNBC, (12.9 vs 8.2 months, HR=0.74 [95% CI, 0.60, 0.92]; p=0.006), but not in women with HER2 positive breast cancer (13.5 vs 12.2 months, HR=0.82 [95% CI, 0.62, 1.06]; p=0.135).[1] There were no noticeable differences in the tolerability and safety data previously shown in the EMBRACE study (Study 305) and Study 301.[1]
On 3 July 2014, The European Commission (EC) issued Marketing Authorisation Approval (MAA) for eribulin in the treatment of patients with locally advanced or metastatic breast cancer (MBC) who have progressed after at least one chemotherapeutic regimen for advanced disease. Prior therapy should have included an anthracycline and a taxane in either the adjuvant or metastatic setting, unless patients were not suitable for these treatments.[6] This decision was based on clinical evidence from EMBRACE (Study 305)[2] and Study 301.[3]
Eisai is dedicated to the discovery, development and production of innovative oncology therapies that can make a difference and impact the lives of women and their families. This passion for people is part of Eisai's human health care (hhc) mission, which strives to better understand the needs of patients and their families to increase the benefits health care provides.
Halaven(R) (eribulin)
Eribulin is the first in the halichondrin class of microtubule dynamics inhibitors with a novel mechanism of action. Structurally eribulin is a simplified and synthetically produced version of halichondrin B, a natural product isolated from the marine sponge Halichondria okadai. Eribulin is believed to work by inhibiting the growth phase of microtubule dynamics which prevents cell division.
Eribulin is indicated for the treatment of women with locally advanced or metastatic breast cancer who have progressed after at least one chemotherapeutic regimen for advanced disease. Prior therapy should have included an anthracycline and a taxane in either the adjuvant or metastatic setting, unless patients were not suitable for these treatments.[6]
305/301 Pooled Data[1]
The pooled analysis included data from EMBRACE (Eisai Metastatic Breast Cancer Study Assessing Treatment of Physician's Choice (TPC) Versus Eribulin) and involved women who received 2-5 lines of chemotherapy for advanced disease. In this third line setting, women were randomised 2:1 to receive eribulin (1.23 mg/m2 iv on days 1 and 8 every 21 days) or TPC. The second study in the pooled analysis (study 301) included women who had received 0-2 prior chemotherapies for advanced disease who were randomised 1:1 to receive either eribulin (dose schedule as per EMBRACE) or capecitabine (1.25 g/m2 orally twice daily on days 1-14 every 21 days). The objective of this pooled analysis was to assess overall survival in the overall ITT population and in subgroups based on HER2 and hormone-receptor status.
Global Phase III Study 305 (EMBRACE)[2]
EMBRACE (Eisai Metastatic Breast Cancer Study Assessing Treatment of Physician's Choice (TPC) Versus Eribulin E7389) was an open-label, randomised, global, multi-centre, parallel two-arm study designed to compare overall survival in women treated with eribulin versus a TPC arm. TPC was defined as any single-agent chemotherapy, hormonal treatment or biologic therapy approved for the treatment of cancer; or palliative treatment or radiotherapy administered according to local practice. The study included 762 participants with MBC who previously had been treated with at least two and a maximum of five prior chemotherapies, including an anthracycline and a taxane. The vast majority (96%) of participants in the TPC arm received chemotherapy.
In the total Phase III EMBRACE study population, eribulin was shown to prolong median overall survival in heavily pre-treated women with MBC compared to women receiving TPC by 2.7 months (13.2 vs 10.5 HR 0.81 (95% CI 0.67, 0.96) nominal p=0.014). A pre-planned analysis of participants from Region 1 of the study (North America/Western Europe/Australia) showed a significant median overall survival benefit of eribulin over TPC of 3.0 months (nominal p=0.031).
The most commonly reported adverse reactions among people treated with eribulin in the EMBRACE study were fatigue (asthenia), a decrease in infection-fighting white blood cells (neutropenia), hair loss (alopecia), numbness and tingling in arms and legs (peripheral neuropathy), nausea and constipation. Peripheral neuropathy was the most common adverse event leading to discontinuation from eribulin, occurring in less than 5% of the women involved in the EMBRACE trial. Neutropenia only led to eribulin discontinuation for 0.6%. Death due to serious side effects, discontinuation and dose interruptions to treatment were lower in the eribulin arm of the trial compared with the TPC arm.
Global Phase III Study 301[3]
Study 301 was an open-labelled, randomised, two-parallel-arm, multicentre study of eribulin versus capecitabine in 1,102 women with locally advanced or metastatic breast cancer previously treated with anthracyclines and taxanes, either in the (neo) adjuvant setting or for locally advanced or metastatic disease. Women in the study received zero to two previous chemotherapies for advanced disease.
The study opened in 2006 and the last patient was randomised in 2010. Patients were randomised to treatment with either eribulin 1.23mg/m2 (administered intravenously over two to five minutes on days 1 and 8, every 21 days) or capecitabine 2.5g/m2 (administered orally twice daily in two equal doses on days 1 to 14, every 21 days).
Study 301 had a co-primary endpoint of overall survival and progression free survival. The study demonstrated a trend favouring improved overall survival with eribulin compared to capecitabine in the ITT population, although the improvement was not statistically significant. Women treated with eribulin had a median overall survival of 15.9 months (HR 0.879; 95% CI: 0.770-1.003; p=0.056) versus 14.5 months with capecitabine. The trial did not meet the pre-specified endpoint for progression-free survival, with 4.1 and 4.2 months for eribulin and capecitabine respectively (HR 1.079; 95% CI: 0.932-1.250; p=0.305).
1-,2- and 3- year overall survival rates for eribulin versus capecitabine showed an early improvement which was maintained throughout the study (1 year, 64.4% eribulin vs 58.0% capecitabine (P=0.0351), 2 year 32.8% eribulin vs 29.8% capecitabine (P=0.324), 3 year, 17.8% eribulin vs 14.5% capecitabine (P=0.175).
Unlike studies conducted today, Study 301 included all women regardless of their human epidermal growth factor receptor 2 (HER2), oestrogen receptor (ER) or progesterone receptor (PR) status. Patients are usually tested for their HER2 status as there are now effective treatments specifically for patients with the HER2 mutation. HER2 positive patients would generally be treated with anti-HER2 positive targeted therapy. For women with HER2 negative MBC (n=755), overall survival was 15.9 months for eribulin vs 13.5 months for capecitabine (HR 0.838; 95% CI: 0.715-0.983). In the HER2 positive population, overall survival was 14.3 months for eribulin vs 17.1 months for capecitabine (HR; 95% 0.965; CI: 0.688-1.355).
Adverse events in Study 301 were consistent with the known profile of both drugs.
Metastatic Breast Cancer and the HER2 Protein
Over 300,000 women are diagnosed with breast cancer in Europe every year, of whom about one third subsequently develop metastatic disease.[7],[8]Metastatic disease is an advanced stage of the disease that occurs when cancer spreads beyond the breast to other parts of the body.
HER2 is a protein that is found on the surface of cells. In HER2-positive breast cancer there is more (over expression) of this protein found on the surface of tumour cells compared with normal breast cells. This protein can be targeted with HER2 targeted therapies such as Herceptin, in people who overexpress HER2, but not in people with normal levels of HER2 protein (HER2-negative) breast cancer. Breast cancers are routinely tested for the presence of HER2 to decide the most appropriate treatment. Triple-negative breast cancer (TNBC) refers to any breast cancer that does not express the genes for oestrogen receptor, progesterone receptor and HER2.