Targeted therapies are drugs or other substances that interfere with specific molecular pathways involved in cancer cell growth and survival. Traditional (cytotoxic) chemotherapy drugs, by contrast, act against all actively dividing cells. Targeted cancer therapies that have been approved for use against specific cancers include agents that prevent cell growth signaling, interfere with tumor blood vessel development, promote the death of cancer cells, stimulate the immune system to destroy cancer cells, and deliver toxic drugs to cancer cells.
There are many types of targeted agents and they can be grouped in different clusters. The EGFR-, TK-, mTOR-, BRAF-, PARP-, CTLA4-, and MEK inhibitors are discussed in this chapter; even more inhibitors are currently available. The numbers of targeted agents are growing rapidly.
In the palliative setting, the first targeted agents prolonged the survival a couple of weeks to months, targeted therapy now appears to be effective for a couple of month to years. They seem also effective in the adjuvant setting (trastuzumab). Several treatment schemes are used, mono or in combination with chemo- and hormonal therapy. Sequential use of chemo- or hormonal therapy is also being used. In general, treatment should continue as long as it is beneficially or until the patient cannot accept the side effects anymore. Increasingly, studies and clinical protocols are including targeted therapies as part of active treatment protocols in combination with radiation, chemo-, and other targeted therapies.