Targeted therapies differ from chemotherapy in that they are designed to specifically block specific aspects of tumor or cell biology, rather than destroy more rapidly reproducing cells more indiscriminately, as in the case of chemotherapy.

Cancer cells are cells in our own bodies that have stopped responding to a natural control and start to grow rapidly. This makes it very difficult to find unique characteristics of tumor cells, which normal cellsdo not have,in order to develop drugs directed against them. For this reason, there are not many drugs of this type.

Biological treatments only damage cancer cells, blocking the genes or proteins found within them. They generally do less harm to healthy cells because these treatments work in a targeted way against cancer cells. These new drugs can be administered alone, although they are almost always accompanied by standard chemotherapy over a period of time.

These biological treatments prevent cells from multiplying, selectively attacking tumor cells without causing side effects in healthy cells. Trastuzumab –Herceptin– is one example of this, and it is the first to have been developed for breast cancer.