Lead researcher Prof. Judith Bliss, of the Institute of Cancer Research (ICR) in the UK, and colleagues recently presented the results of their EPHOS B Trial at 10th European Breast Cancer Conference (EBCC-10) in Amsterdam, the Netherlands.
After skin cancer, breast cancer is the most common cancer among women in the US. It is estimated that 1 in 8 American women will be diagnosed with an invasive form of the disease at some point in their lives.
According to the American Cancer Society, around 1 in 5 breast cancers are human epidermal growth factor receptor 2-positive, or HER2-positive. This means the cancer tumors have too many copies of the HER2 gene, resulting in excess production of the HER2 protein.
Compared with other breast cancers, HER2-positive breast cancers tend to spread faster and more aggressively, and patients with this type of cancer are more likely to experience recurrence following treatment.
Current treatments for HER2-positive breast cancer include surgery, chemotherapy and hormone therapy. There are also drugs available that target and block the HER2 receptors on breast cancer cells, such as trastuzumab (brand name Herceptin), which is the most common medication for HER2-positive breast cancer.
In recent years, new anti-HER2 drugs have entered the market, including lapatinib (brand name Tyverb or Tykerb), though this drug is currently only used to treat advanced HER2-positive breast cancer.
For their study, Prof. Bliss and colleagues set out to investigate how trastuzumab and lapatinib affected HER2-positive breast cancer tumors in the short window between diagnosis and surgery.
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The team enrolled 257 women who had been diagnosed with HER2-positive breast cancer and allocated them to one of three treatment groups for the 11 days between diagnosis and surgery; one group received trastuzumab, one group received lapatinib and the final group received no treatment, representing the control group.
However, previous research has suggested that a combination of trastuzumab and lapatinib may be effective against HER2-positive breast cancer. As such, the team amended the trial halfway through, so that women in the lapatinib group also received trastuzumab.
Before and after the 11-day treatment period, the researchers measured biological markers of cellular proliferation in the women’s breast cancer tumors, including levels of the ki67 protein and apoptosis – programmed cell death.
However, they found that for around a quarter of the 66 women who received both trastuzumab and lapatinib, their tumors were too small to measure cellular proliferation.
The team found that 17% of women treated with the drug combination had minimal residual disease – defined as a tumor that is smaller than 5 mm in diameter – while for a further 11%, the drugs had eradicated their tumors, representing a complete pathological response.
In comparison, minimal residual disease or a complete pathological response was identified in just 3% of women treated with trastuzumab only, while neither response was identified among women in the control group.
The team notes that many of the women who responded to the combination therapy had stage 2 breast cancer, where the cancer has spread to the lymph nodes.