Promising results in immunotherapy trial for aggressive metastatic breast cancer

Cancer
metastatic breast cancer

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At the ESMO 2018 Congress, researchers reported promising results from an immunotherapy trial in patients with aggressive metastatic breast cancer.

According to the World Cancer Research Fund statistics, breast cancer is the most commonly occurring cancer in women, with over two million new cases in 2018. There are many different types of breast cancer. Identifying which type of tumor a patient has allows doctors to plan the best treatment approach.

Most breast cancers have receptors on the cancer cell surfaces for the hormones estrogen or progesterone, or they make a protein called HER2. These types of tumor respond to hormone drugs therapies or drug treatments targeting HER2. However, some breast cancers do not have these cell features and are known as triple-negative breast cancer (TNBC).

Although relatively rare, TNBC is the most aggressive form of breast cancer and often affects young women. If a tumor spreads beyond the breast to other parts of the body it is known as metastatic breast cancer. For TNBC, if the tumor becomes metastatic the average survival is 12-15 months.

Many patients with triple-negative breast cancer develop resistance to chemotherapy

The main type of drug treatment for TNBC is chemotherapy that kills cancer cells. However, most patients develop resistance to chemotherapy within a few months. Immunotherapy drugs stimulate the body’s own immune system to attack cancer cells. A combination of chemotherapy and immunotherapy could offer another option for these patients.

The IMpassion130 trial is an international trial investigating a combination of the chemotherapy drug nab-paclitaxel and the immunotherapy drug atezolizumab in patients with metastatic TNBC.

Trial tested a combination of chemotherapy and immunotherapy

Atezolizumab is thought to act by targeting a protein on tumor cells called PD-L1 that suppresses the immune system response. By blocking PD-L1, atezolizumab “releases the brake” on the immune system, allowing it to attack cancer cells. These types of immunotherapy drugs are called “immune checkpoint inhibitors”. The IMpassion130 trial researchers reported its interim findings at the recent European Society of Medical Oncologists (ESMO) 2018 Congress.

The study included 902 women with metastatic TNBC. The researchers allocated the patients to receive standard chemotherapy (nab-paclitaxel) plus the immunotherapy drug atezolizumab, or standard chemotherapy plus placebo. The researchers followed the patients to see whether the drug combination could slow cancer growth (progression-free survival) and prolong overall survival. They analyzed the effect in all the study participants, and in the subgroup of patients who had tumors expressing the PD-L1 protein.

Encouraging results from clinical trial

In the entire study population, the average progression-free survival was 7.2 months in the combination therapy group and 5.5 months in the chemotherapy alone group. In the PD-L1 subgroup, the average progression-free survival was 7.5 months with combination therapy and 5.0 months with chemotherapy alone. In the entire study population, overall survival was 21.3 months with combination therapy compared to 17.6 months with chemotherapy alone, which did not reach statistical significance.

However, in patients with PD-L1 positive tumors the average overall survival was 25 months with combination therapy compared to 15.5 months with chemotherapy alone, which was statistically significant. The combination therapy was well tolerated, with most of the side effects related to the chemotherapy rather than the immunotherapy drug.

The researchers are encouraged by these promising interim results from the IMpassion130 trial. Immune therapy on top of standard chemotherapy prolonged survival by 10 months in patients with tumors expressing PD-L1. The lead investigator Professor Peter Schmid commented that “this combination should become a new treatment option for patients with metastatic TNBC” and will change the way these patients are treated.

Several ongoing trials investigating other combination chemotherapy and immunotherapy options

Commenting for ESMO, Dr. Marleen Kok from The Netherlands Cancer Institute in Amsterdam agreed that the gain in overall survival seen with combination therapy was impressive and will probably change the treatment landscape for patients with metastatic TNBC. She noted that there are several trials ongoing to investigate other combination chemotherapy and immunotherapy options in metastatic breast cancer and also in early breast cancer patients. These will help to answer questions about the best combination therapies for breast cancer patients.

Written by Julie McShane, Medical Writer

Reference: Press release: Some patients with metastatic triple negative breast cancer live longer with immunotherapy (ESMO 2018 Press Release) https://www.esmo.org/Press-Office/Press-Releases/IMpassion130-atezolizumab-nab-pac-triple-negative-breast-cancer-Schmid

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