Chemotherapy is a medication or combination of medications used to treat cancer. Chemotherapy can be given orally (as a pill) or injected intravenously (IV). When chemotherapy drugs enter the bloodstream, it destroys cancer cells. Chemotherapy is particularly useful for cancers that have metastasized, or spread. Chemotherapy attacks all quickly-dividing cells, regardless of whether they are cancerous which can cause a number of side effects, including hair loss, mouth sores, loss of appetite, nausea and vomiting, diarrhea, and low blood counts. Low blood counts can increase a patient’s risk of infection, bruising or bleeding, fatigue, and shortness of breath. The side effects of chemotherapy are generally temporary and often go away once treatment is completed. Chemotherapy regimens vary from patient to patient. They are generally repeated several times in cycles, with three to four weeks separating each cycle to allow damaged normal cells time to recover. After the first two or three sessions of chemotherapy, patients may have a CT or PET scan to see if the drug(s) is effective. If the drug(s) is not working, it may be switched out for a new drug(s).