Over the past few years, a new class of drugs called targeted therapies, which focus on interfering with the inner workings of the cell, have been developed. They interfere with the inner workings of the cell such as the development of blood vessels, growth and cell division. Unlike chemotherapy, which kills both healthy cells and cancer cells, targeted therapies attach to cancer cells primarily. Therefore, different and fewer side effects are associated with targeted therapies.
In normal cells, signals command the proteins to perform certain task to promote the growth, death, or development of the cell. The proteins work as a team to carry out the work of the cell. In cancer cells the proteins may not respond to normal signals, may over-respond to normal signals, or otherwise fail to carry out their normal functions. Cancer develops when proteins inside a cell cause it to reproduce excessively and allow that cell to live longer than normal cells.
Researchers have identified that certain cancers have an overabundance of certain proteins while normal cells do not. This has allowed for the development of new drugs that "target" the proteins in the cancer cells and halt their growth. There are several classes on targeted therapies for cancer therapy: Monoclonal Antibodies, Epidermal Growth Factor Receptors Inhibitor (EGFR), Tyrosine Kinase Inhibitors, Proteasome Inhibitors, and Angiogenesis Inhibitors/Vascular Endothelial Growth Factors (VEGF). All of these drugs target a specific protein that is found in certain cancer cells.
For example, Gleevec (imatinib), which is used for the treatment of certain types of intestinal tumors and chronic myelogenous leukemia (CML), was the first targeted therapy approved by the FDA. It targets the protein, bcr-abl tyrosine kinase. Prior to the approval of imatinib, the standard therapy for CML did not have good cure/control rates and caused many side effects. Up until recently metastatic kidney cancer has not had very effective therapies. Within the last year, two new targeted therapies have been approved for this disease. These two drugs have given kidney cancer patients new options and hope.
Since these drugs "target" proteins that are not found in normal cells or at very low levels, the side effects are often fewer than with conventional chemotherapy. The most common side effect seen with these drugs are a rash that covers the face, neck and chest. It can be bothersome and interfere with body image. It is often treated with topical creams and oral antibiotics. However, the rash is usually an indication that the drug is working. If the drugs interfere with the production of blood vessels (VEGF), there can be a risk for bleeding or blood clots. Other side effects can include nausea, vomiting, fatigue and diarrhea.
Although these targeted therapies are effective against cancer, they are often given in combination with conventional chemotherapy to work synergistically. The development of targeted therapies has given certain cancers that had few effective treatments new options. Numerous clinical trials are ongoing to study new targeted therapies and new indications for those already available. If you would like more information on targeted therapies or clinical trials, please call the cancer program at 814.231.7005. You can also find more information on the National Cancer Institute website or the American Cancer Society website.
Tara Baney, RN, MS, AOCN, is an Oncology Clinical Nurse Specialist in Mount Nittany Medical Centers Cancer Program.