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Thursday, May 10, 2007

Chemotherapy Treatments

The principles behind treating cancer with chemotherapy are a bit like a scorched earth strategy, denying the enemy sustenance in the expectation that cancer needs resources more than healthy tissues do.

Most cancer chemotherapy is applied systemically, meaning it is applied to your whole body via the circulatory system. The easiest way to deliver systemic chemotherapy is to ingest it in pill or liquid form via the digestive system. This approach works only for those chemicals that can survive the rigors of being digested in the stomach, and then only if the molecules are small enough to be absorbed into the circulatory system by the intestines.

The molecular structures of many chemotherapy agents are too fragile to allow the drug to be taken this way, or they are too large to be absorbed into the blood stream through the intestines. Therefore, most chemotherapies are given by an injection or an intravenous drip along with saline solution on a specific timetable. Your entire body is therefore exposed to the effects of a systemic poison and not just the cancer in a specific location. This can be an important benefit of a systemic treatment if the cancer has already metastasized and begun to move to secondary areas or other organs. Once in the blood stream, the chemical agents can go wherever your circulatory system can reach.

Since organs like the brain, kidneys, lungs, and liver are also exposed to the toxic effects of these drugs, dosages need to be carefully controlled so as not to kill healthy cells along with the cancer cells. Antidotes can also be given in advance for some chemotherapy agents that are known to carry high risks of morbidity to organs like the kidneys or liver. Since excreting these systemic poisons as quickly as possible is important, having healthy kidneys may dictate whether chemotherapy is an option.

The most effective alternative to systemic application is a regional or localized application where higher doses of the drugs can be administered directly to the affected area or organ. There are two variations to this technique of controlling the application of chemotherapy to specific surfaces. The first method is direct application and the second is intra-cavitary application via a special shunt or tube that is used to feed the chemicals directly into the peritoneal space. Both of these techniques allow much higher doses of chemicals to be used since most of the drug remains outside of the bloodstream, coating only the exposed tissue surfaces.

Some absorption of the chemo into the affected surfaces is necessary for it to work. For chemotherapy given in this manner during surgery, the surgeon will sometimes take tissue samples to analyze how deeply the drug has penetrated the tissue wall. Since penetration of the cell wall implies some entry of chemo into the bloodstream, the use of an antidote is an important precaution.

Which approach is used depends upon the goals of the treatment and the need to control side effects. In any case, the application methods are carefully selected to ensure that more damage happens to the cancer cells than to the healthy cells. Chemotherapy works because the rapid growth of cancer cells makes them more vulnerable to chemicals that block, destroy or interfere with fast growing cells.

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