All chemotherapy drugs are systemic , meaning they treat the entire body by traveling through the system of blood vessels . Therefore doctors cannot target specific areas of cancer. This is both good and bad. It is good because if there are small, undetected pieces of cancer, metastases , that have broken off the primary cancer and spread to other parts of the body, the drugs can eliminate them. It is bad because the chemotherapy drugs also effect the normal tissues of the body.
Chemotherapy works against cancer because it attacks cells that are rapidly dividing .
As we discussed in the Introduction, cancer is made of cells dividing rapidly and out of control. The rapidly dividing cells produce certain chemicals that allow them to continue to divide. Chemotherapy drugs work specifically to block or disrupt these chemicals to kill cells that are dividing. The problem is that your normal cells are also dividing. The chemotherapy drugs cannot tell the difference between normal, dividing cells, and cancerous, dividing cells.