How does chemotherapy work?

Chemotherapy is the administration of certain toxic drugs in an attempt to kill cancer cells and cure patients of their cancer, shrink tumors to facilitate surgical resection or prolong a patient's life. Chemotherapy is typically administered for high grade bone sarcomas. It is usually given before surgery (preoperative chemotherapy=neoadjuvant chemotherapy=induction chemotherapy) to try to kill the tumor before taking it out. The terms induction chemotherapy and neoadjuvant chemotherapy refer to giving the chemotherapy before surgery. Giving chemotherapy before surgery makes it easier to remove the tumor and makes it less likely for the tumor to come back in the area where it was removed. At the same time, any microscopic tumor cells that have spread throughout the body are killed. Certain tumors may shrink dramatically following chemotherapy which makes the surgery easier. Less normal tissue is removed. Preoperative chemotherapy also permits us to examine the response that the tumor had to the chemotherapy which helps us estimate the patient's prognosis (it helps us estimate the response of the microscopic tumor cells that have already spread). Preoperative or induction chemotherapy is largely responsible for our present day ability to save 90%-95% of limbs with high grade sarcomas instead of performing amputations. Amputations for high grade bone sarcomas are rarely performed nowadays.

For high grade bone sarcomas, chemotherapy is also usually given postoperatively. When it is given postoperatively, it is referred to as adjuvant chemotherapy. The same chemotherapy agents are used before and after surgery. The purpose of chemotherapy is to kill any tumor cells that have spread throughout the body that can grow and kill the patient. By killing or eradicating these cells, the patient can be cured of the cancer. The entire chemotherapy regimen may require 6 months to 12 months to complete. Some chemotherapy agents require a hospital admission for a few days in order to administer the medications. The following chemotherapy drugs may be used in the treatment of sarcomas: Adriamycin (doxorubicin), ifosfamide, cisplatin, high dose methotrexate, cyclophosphamide, vincristine, actinomycin-D, etoposide. There are complications that are specific to each type of medication. These complications should be thoroughly discussed with the medical oncologist. Some of the general complications or side effects include: hair loss, nausea and vomiting, mucositis, myelosuppression/decrease in the blood counts (neutropenia=drop in white blood cells; anemia=drop in red blood cells; thrombocytopenia=drop in platelets), cardiac dysfunction, hearing loss, kidney failure, neuropathy. Many of these side effects and complications can be minimized with specific medications. Prior to initiating chemotherapy several blood tests will be ordered along with a hearing test and an echocardiogram (asseses the function of the heart). Blood tests will be required frequently throughout the course of the chemotherapy regimen to follow kidney function and blood counts. A special intravenous line will be placed (port-a-cath or groshong) that can stay in place for prolonged periods. This line is directed into the large veins that empty into the cardiopulmonary circulation. It is necessary to place these lines so the chemotherapy can be administered directly into the large veins. Infusion of chemotherapy agents into small veins causes destruction of the small veins. Additionally some agents may spill under the skin and cause skin damage. The patient and family members must be aware that these ports can get infected when the patient's white blood cell count drops. Any fever that develops during chemotherapy must be reported to the oncologist, the patient will be admitted, cultures of the blood obtained along with a chest X-ray and urinalysis to check for bacteria. The patient will be started immediately on intravenous antibiotics. If a line gets infected postoperatively in a patient who has had a prosthetic replacement, the line should be removed. Bacteria can live for long periods on the part of the line that is in the venous sytem. Intravenous antibiotics may not eradiacte the bacteria and the bacteria can spread to the prosthesis and cause a severe limb threatening infection that requires additional surgery and is difficult to cure without removing the prosthesis (impossible to cure with intravenous antibiotics alone without removing the prosthesis).