How Does Chemotherapy Work?
According to the National Cancer Institute, almost all normal cells grow and die in a controlled way through a process called apoptosis. Cancer cells, on the other hand, keep dividing and forming more cells without a control mechanism to induce normal apoptosis.
Anticancer drugs destroy cancer cells by stopping them from growing or dividing at one or more points in their growth cycle. Chemotherapy may consist of one or several cytotoxic drugs that kill cells by one or more mechanisms. The chemotherapy regimen chosen by most conventional oncologists is based on the type of cancer being treated. As you will read later in this protocol, there are factors other than the type of cancer that can be used to determine the ideal chemotherapy drugs that should be used to treat an individual patient.
The goal of chemotherapy is to shrink primary tumors, slow the tumor growth, and kill cancer cells that may have spread (metastasized) to other parts of the body from the original, primary tumor. However, chemotherapy kills both cancer cells and healthy normal cells. Oncologists try to minimize damage to normal cells and to enhance the cell killing (cytotoxic) effect on cancer cells. Too often, unfortunately, this delicate balance is not achieved.
Clinical studies show that for certain types of cancer chemotherapy prolongs survival and increases the percentage of patients achieving a remission. A partial remission is defined as 50% or greater reduction in the measurable parameters of tumor growth as may be found on physical examination, radiologic study, or by biomarker levels from a blood or urine test. A complete remission is defined as complete disappearance of all such manifestations of disease. The goal of all oncologists is to strive for a complete remission that lasts a long time--a durable complete remission, or CR. Unfortunately, the vast majority of remissions that are achieved are partial remissions. Too often, these are measured in weeks to months and not in years. Some types of cancer do not show any meaningful response to chemotherapy.