Metastatic breast cancer drugs may delay chemotherapy

F or patients with metastatic breast cancer, knowing that the cancer has spread to other parts of the body can mean dreaded chemotherapy regimens and their difficult side effects. However, some patients, with hormone receptor-positive metastatic breast cancer and HER2-negative metastatic breast cancer, may delay chemotherapy for breast cancer in some cases for up to a year if they receive hormone therapy. Now some of these patients may have a longer respite, deferring chemotherapy for more than two years, thanks to a new class of drugs approved for metastatic breast cancer.

“This is one of the biggest advances we’ve had in metastatic breast cancer in a long time.” – Saramila Ethal, MD, Hematologist and Oncologist, Medical Oncology

What are kinase inhibitors?

These newer drugs belong to a common class of anticancer drugs for targeted therapy called kinase inhibitors. A kinase is a protein in the cell that acts as a transmitter, receiving signals from other cells and then transmitting instructions to the nucleus of your cell. Once the signal is sent, the cell can perform any number of functions, including growth, division, or even closing. These breast cancer drugs target two protein kinases, CDK 4 and CDK 6, which help regulate cell growth and division. Blocking these proteins can help slow the growth of cancer cells. Some patients with HR-positive and HER-negative metastatic breast cancer have experienced favorable results when combined CDK 4/6 inhibitor and hormonal therapy.

Saramila Aythal, MD, a hematologist and oncologist, medical oncologist and director of the Breast Cancer Center at our Philadelphia hospital says. “But by adding this other treatment that targets CDK 4/6, they have had better responses for more than two years. Importantly, many people who will receive chemotherapy for metastatic cancer, especially if it has invaded an organ, such as the liver or with this combination of treatment, were able to of putting off chemotherapy for up to 27 or 28 months. It made a huge difference.”

CDK 4/6 Inhibitors:

To date, the FDA has approved three CDK 4/6 inhibitors for the treatment of metastatic breast cancer:

• Palbociclib (Ibrance ^® ), approved in 2015
• Ribociclib (Kiskali® ⁾ , approved April 2017
• Abemaciclib (Verzenio™), approved September 2017

Palbociclib and ribociclib are usually given together with the anti-estrogen drug fulvestrant (Faslodex ^® ) that regulates the hormones. Abemaciclib is the first CDK 4/6 inhibitor approved as a standalone therapy. CDK 4/6 inhibitors are only approved for HER-positive and HER-negative breast cancer, but clinical trials are underway to determine if they can be used to treat other cancers, including lung, prostate, and other types of breast cancer. Common side effects of these inhibitors include diarrhea, nausea, and fatigue. “These are oral medications that are easy to take, and are very well tolerated,” says Dr. Ethal. “It’s a huge paradigm shift in the way we treat breast cancer.”