The targeted agent neratinib (PB272), which is still in clinical trials, demonstrated an improvement in cancer-free survival when used after Herceptin® (trastuzumab) in early-stage, HER2-positive breast cancer.
Approximately 20-30% of breast cancer is referred to as human epidermal growth factor receptor-2 (HER2)-positive. This means that the breast cancer cells have too many HER2 proteins on their surface, which stimulates the cancer cells to grow and spread.
Agents targeting the HER2 proteins and HER2 pathway have been approved for the treatment of HER2-positive breast cancers. These agents reduce the excessive biochemical signaling that stimulates cancer growth and spread in HER2-positive cancers.
Trastuzumab is a commonly used agent in breast cancer that is targeted against HER2 proteins. It has demonstrated improvements in outcomes among patients with HER2-positive breast cancers, including early-stage breast cancers.
Neratinib is a novel agent referred to as a tyrosine kinase inhibitor that is targeted against several biochemical pathways implicated in the growth and spread of cancer. Specifically, neratinib is targeted against the HER1, HER2, and HER4 pathways, and is currently in phase III clinical trials.
Researchers recently conducted a clinical trial to further evaluate neratinib in early breast cancer. This trial, referred to as the exteNET trial, included 2,840 patients from 41 countries with HE2-positive early breast cancer who had received treatment with surgery, followed by treatment including trastuzumab.
Following the completion of therapy with trastuzumab, one group of patients in the trial received further treatment with neratinib, while the other group of patients received placebo (inactive substitute) for one year.
- Among patients treated with neratinib, survival rates without an invasive recurrence of cancer were as follows: approximately 94% at 2 years; 92.5% at 3 years; 91.4% at 4 years; and 90.4% at 5 years.
- Among patients who received placebo, the survival rates without an invasive recurrence of cancer were as follows: 91.6% at 2 years; 90.3% at 3 years; 89.2% at 4 years; 87.9% at 5 years.
Among the group of patients with hormone-receptor positive (HR-positive) breast cancer (meaning the patient’s breast cancer is stimulated to grow from exposure to the female hormones estrogen and/or progesterone), the survival rates without an invasive recurrence of cancer were as follows:
- 8% at 3 years; 92.9% at 4 years; and 91.7% at 5 years among those who were treated with neratinib
- 9% at 3 years; 88.6% at 4 years; and 86.9% at 5 years among those who received placebo.
These results indicate that neratinib improves survival without a recurrence of invasive cancer among patients with early-stage, HER2-positive breast cancer who have completed treatment with surgery and Herceptin.
Although neratinib is not yet approved by the FDA, it represents a potential for additional treatment options among women with breast cancer.
Reference: Puma Biotech Inc. News Release. Puma Biotechnology Announces Interim 5-Year Disease Free Survival Data from Phase III Trial of PB272 (Neratinib) in Extended Adjuvant HER2-Positive Early Stage Breast Cancer (ExteNET Trial). Available at: http://www.pumabiotechnology.com/pr20160721_2.html. Accessed July 25, 2016.
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