Considered a precision medicine, targeted therapy stops molecular mutations on cancer cells to prevent them from growing and spreading. These therapies allow medications to kill cancer cells and leave most other cells alone by focusing on specific traits of the cancerous cells of a person’s tumor. These traits can sometimes be found on normal cells as well, leading to side effects, but typically not as severe or extensive as those experienced with chemotherapy because less cells are affected.
Targeted therapies are approved to treat a variety of cancer types, including breast cancer. Two people with the same type of cancer may have different molecular targets, meaning the treatment is not universally effective for a cancer type—and even if a mutation is present, the cancer may not respond to the treatment. Common molecular mutations (called targets) that are treated with targeted therapies include HER2, EGFR, KRAS, VEGF, ALK, JAK 1 and 2, BTK, and BRAF.
Targeted therapies are categorized as either small molecule or large molecule drugs. Small molecule drugs find the molecular target, enter the cell, and then block it. Large molecule drugs are too big to enter the cell—instead, they find the molecular target and do damage to proteins and enzymes on the surface of the cell.
DNA is naturally damaged during the cell cycle, and that damage must be repaired to prevent cell death—even in cancer cells. PARP inhibitors increase the effectiveness of chemo and/or radiation therapies by inhibiting DNA repair. This therapy is often prescribed to those with breast, ovarian, fallopian tube, or peritoneal cancer, among other types.
This therapy works by blocking signals within cancer cells, preventing a step they need in order to grow and divide.
Angiogenesis occurs when a tumor develops its own blood and nutrient source. This medication blocks the formation of the blood vessels that supply the tumor. Some kinase inhibitors also act as angiogenesis inhibitors.
This targeted immunotherapy consists of antibodies created in a laboratory that target a specific protein on the surface of a cancer cell to mark it as cancerous. They may also block a receptor that is important for cell growth.
This is a combination of radiation and monoclonal antibodies that delivers radiation directly to the tumor cells, often in lower doses and over a longer period of time.
Side effects of targeted therapy vary from person to person and depending on the treatment, and some experience no side effects at all. Some of the medications can cause birth defects, so it is important for the care team to discuss fertility planning and preservation with those who are of childbearing age.