Minimal Side Effects with New Class of Breast Cancer Drugs

Recently, hormonal therapies have been making major breakthroughs as a new type of oral drug becomes available as a treatment option for breast cancer.

These new drugs are called cyclin-dependent kinase (CDK) inhibitors, and they are both effective and produce little to no side effects for most patients. 

One of the most prevalent forms of breast cancer is hormone receptor-positive (HR+) metastatic breast cancer. In these cases, the cancer can be treated with hormone therapies that block the hormones produced and used by cancer cells. The result is usually a drastically slowed progression of the cancer and, in particularly effective treatments, cancerous tumors have even stopped growing altogether.

Hormonal therapies typically block the distribution of estrogen throughout the body, which cancerous tumors depend upon in order to grow. In some cases, cancer will circumvent hormonal therapy and become resistant to hormone blockers, but this does not produce negative consequences, nor does it encourage the cancer’s growth.

In addition to an HR+ diagnosis, breast cancer patients will receive an HER2+ or HER2- diagnosis, which indicates the presence of the HER2 protein. When present, this protein promotes the growth and spread of cancer cells. An HER2+ diagnosis occurs in approximately one out of every five cases of breast cancer and is generally a more aggressive form that is less responsive to hormone therapy. However, over 70% of breast cancer diagnoses are HR+/HER2- breast cancer, and this type is typically responsive to hormonal therapy and is considered more treatable.

With the recently introduced hormonal therapies, there has been a major revolution with this therapy coming out as a new kind of oral drug to be made available as a treatment method. These new forms of medication are known as cyclin-dependent kinase, or CDK, inhibitors. The drugs are known to be effective and, at the same time, produce very little or no side effects in patients. Hormonal therapies are known to cause a blockage in the distribution of estrogen throughout the entire body, and cancer-causing tumors are mostly dependent on this hormone in order to grow. In some cases, the cancer can become resistant to these hormonal therapies, but it would not cause any negative results, nor would it in any way make the cancer growth stronger.

In recent years, a new oral drug has been introduced, called CDK. There has been research conducted on these HR+ inhibitors, and the first drug was introduced in 2015 and was marketed under the name Ibrance. In 2017, another drug called ribociclib was also approved under the brand name Kisqali. Currently, there are clinical trials going on for a third kind of CDK inhibitor, which may get approved sometime in the next year. It is named abemaciclib, and this medicine, along with the previous two drugs, has been called a breakthrough therapy by the reviewers who approved the drugs.

The main function of a CDK inhibitor is to cause an interference in the ability of the cancer cell to split up and multiply, which halts the spread of cancer-causing cells in the entire body. These inhibitors are from a different theory than the endocrine ones since they are known to have separate and unique side effects. However, along with its own set of side effects, they do have a common one, that of lowering one’s white blood cell count, which is known as neutropenia. We all are aware that white blood cells play an important role in the immune system, and any changes in the count can lead to infection. But the consumption of a CDK inhibitor does not cause any permanent side effects on the body. This white blood cell side effect is not seen as an issue in the third kind of CDK drug, however, some of its other common side effects include diarrhea and fatigue. Although there can be a mild form of side effects with CDK inhibitors, there are not any serious ones that could lead to a disruption in the day-to-day activities of the individual. Even though CDK inhibitors have been majorly tested on breast cancer patients, research is still being conducted on their application with other types of cancer, such as prostate cancer, lung cancer, and ovarian cancer.

As the new CDK is still in the approval stage, those who are diagnosed with breast cancer would be introduced to the initial two CDK drugs as a treatment option. This breakthrough has led to a deeper understanding of how cancer cells multiply and grow, and so there may be other new solutions in the near future.