Chemotherapy uses powerful anticancer drugs that travel through the bloodstream, making it potentially useful for cancers that have spread. Oncologists use about 50 different chemotherapeutic drugs to combat cancer, generally administering more than one drug at a time because these drugs are more powerful when combined.
Taken orally or injected into the bloodstream, chemotherapeutic drugs interfere with cancer cellsí ability to make new DNA or divide properly. In some cases, the drugs cause programmed cell death.
Many leukemias and lymphomas and cancer of the testicles are successfully treated with chemotherapy. Breast, lung, colorectal, and prostate cancer are not currently curable with chemotherapy alone, so chemotherapy is often used in combination with other therapies. In fact, the most common combination of cancer treatments is surgery or radiation therapy followed by chemotherapy.
Chemotherapy often causes severe side effects, particularly reduced resistance to infection, internal bleeding, diarrhea, nausea, vomiting, hair loss, and insufficient oxygen in the blood, known as anemia. Some tumors develop resistance to many drugs after exposure to just one drug, a condition called multidrug resistance. When this happens, there may be no drugs that are effective against the tumor.