Targeted Cancer Therapy

     Until recently, drugs against cancer were not targeted solely toward cancer cells. Instead, they acted upon ANY fast-reproducing cell in the body.  Thus, chemotherapy drugs often killed normal, healthy cells along with the problematic cells. In the late 1900s, however, a new type of cancer treatment was developed: targeted therapies (Evolution of Cancer Treatments: Targeted Therapy). Targeted therapies are often referred to as “molecularly targeted therapies” or “molecularly targeted drugs” (National Cancer Institute). Targeted therapies work primarily by interfering with cellular processes involved with tumour growth and progression (National Cancer Institute). This type of treatment is still fairly new, and while many drugs are being used as we speak to treat various forms of cancer, there are many others that are still being studied, and yet others that are in the preclinical testing stage (National Cancer Institute). Targeted therapies are being studied as cancer treatments to use on their own as well as with other cancer treatments such as chemotherapy (National Cancer Institute).

     How do targeted cancer therapies work, and what makes them so unique from the common chemotherapy? Targeted cancer therapies interfere with cell proliferation (division) and spread. By targeting proteins that control various functions of the cell such as movement, responses to stimuli and death, they control the unorganized division of cancerous cells and even trigger cancer cell mortality in a process known as apoptosis (National Cancer Institute) – a naturally occurring process in the body that forces cells (such as cancer cells) that have excessive amounts of DNA damage to die.

     Through this process, apoptosis can be caused in a number of ways. For instance, targeted cancer therapies may cause direct cancer cell death by working to specifically trigger the cell’s death. It may also cause the immune system to identify and destroy cancerous cells and may further transport toxic substances directly to cancerous cells to destroy them.

     A few of the earliest targeted cancer therapies include trastuzumab (Herceptin) and gefitinib (Iressa). Both therapies strive to block growth signals (as shown in the image to the right), which are, in essence, “hormone-like substances that help tell cells when to grow and divide” (Evolution of Cancer Treatments: Targeted Therapy). After the 1960s, researchers understood that if these growth factors are abnormally high in the human body, they may contribute to the growth, spread, and development of various forms of cancer; the way in which the body’s cells respond to these growth signals creates changes in the features of normal cells that are normally found only in cancerous cells (Evolution of Cancer Treatments: Targeted Therapy).  Targeted cancer therapies that block growth factors are commonly known as “growth signal inhibitors”.

     Another class of targeted cancer therapies include the angiogenesis inhibitors. Angiogenesis is a term derived from the greek words “angio” (blood vessel) and “genesis” (beginning); to put it simply, angiogenesis is the formation of new blood vessels (Evolution of Cancer Treatments: Targeted Therepy).Typically, this process is both common and safe in the human body. However, in an individual diagnosed with cancer, angiogenesis creates minute blood vessels that provide blood to the tumor and thereby allow for the tumor’s growth. Anti-angiogenesis agents were an idea first proposed in the early 1970s. These agents are forms of targeted cancer therapies that make use of substances such as drugs in order to “stop tumors from making the new blood vessels they need to keep growing” (Evolution of Cancer Treatments: Targeted Therepy). The first angiogenesis inhibitor, bevacizumab (Avastin) was approved in 2004 and is now used to treat “colorectal, kidney, and lung cancers” (Evolution of Cancer Treatments: Targeted Therapy).

     All in all, targeted cancer therapies perform exactly as their name suggests: they ‘target’ only the cancerous cells and cause less harm to normal, healthy cells in the human body (National Cancer Institute). Targeted cancer therapies also have significantly less side effects in comparison to chemotherapy (National Cancer Institute), and it is quite possible that treatments may be individualized to affect “unique molecular targets produced by [each patient’s] tumor” (National Cancer Institute).

     Science is making progress. With the vast amount of change that has occurred in the medical field over the years, it does not seem too far-fetched to say that a cure for cancer may not be too distant in the future. Perhaps, in the future, the prediction of over 72500 deaths that was made for 2013 need never be made again.