Is pyrotinib effective as a second-line treatment in patients with HER2-positive breast cancer in a real-world setting?

The authors evaluated the efficacy and safety of pyrotinib (Irene), for the treatment of HER2- positive metastatic breast cancer (MBC) in a real-world setting. The authors observed that pyrotinib was effective and well tolerated by patients. 

Breast cancer (BC) is the most common tumor in women worldwide. It can be classified depending on the presence of certain proteins on the surface of cancer cells. If BC cells express the HER2 protein on their surface, it is called HER2-positive BC. This type of BC has a more aggressive behavior, high recurrence, and metastasis (spread) compared to BC that does not express HER2 protein. 

HER2 is a protein that helps to control how healthy breast cells grow, divide and repair themself. In HER2-positive BC, cancer cells make too many copies of the HER2 protein, resulting in uncontrolled growth.

HER2-positive BC can be treated with drugs able to block the action of HER2. A treatment option is trastuzumab (Herceptin), a monoclonal antibody that blocks HER2 function. Another available treatment relies on the usage of tyrosine-kinase inhibitors (TKI). TKIs block certain proteins on cancer cells involved in many cell functions such as growth, division, and signaling. An example of a TKI used in HER2-positive BC is lapatinib (Tykerb).

Pyrotinib is a newer TKI able to bind and block HER2 protein. It has shown better effectiveness in patients with HER2-positive BC compared to lapatinib. However, its safety and effectiveness in a real-world setting are still under investigation. 

This study collected data from 64 patients that were diagnosed with HER2-positive metastatic or recurrent BC. They were treated with pyrotinib as a single agent or in combination with chemotherapy. 26 patients were previously treated with trastuzumab, while 11 were treated with lapatinib, after receiving trastuzumab or trastuzumab emtansine (T-DM1; Kadcycla). Patients were followed for 260 days (approximately 8.6 months).

Overall, 73.4% of patients had an objective response (a decrease in tumor size). The disease control rate (DCR) was 98.4%. Disease control is when the tumor shrinks or does not grow or spread. 

Response to treatment was very good in patients with previous trastuzumab treatment (70%) or with brain metastases (72.7%). Previous lapatinib treatment was associated with a significantly lower response to treatment (45.5%).

Overall, all patients experienced side effects. The most common side effects were diarrhea, hand-foot syndrome (redness, swelling, and pain in the hands and soles of the feet), and low white blood cells. 

This study showed that pyrotinib has good effectiveness and is safe in patients with HER2-positive BC that had been previously exposed to trastuzumab. 

The number of patients in this study and the follow-up period was limited. The analysis of the side effects was done by questionnaire. Further studies are needed.