[MOL] Drug Sensitivity Testing [00749] Medicine On Line

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[MOL] Drug Sensitivity Testing

In Vitro Drug Sensitivity Testing

The selection of a drug or drugs to treat an individual cancer patient is based largely on the results of previous clinical research with patients (clinical trials) and the physician's experience. Researchers have attempted to develop in vitro drug sensitivity systems (also called chemosensitivity testing) to predict whether a specific anticancer drug would be effective for a patient. Such a system could help identify the most effective drug(s) for an individual patient and prevent needless side effects caused by the use of ineffective drugs.

Because basic research has yielded new knowledge about how cancer cells behave, it is now possible to grow tumor cells outside the body (in vitro). Cells from a cancer patient's tumor can be grown in test tubes and exposed to various anticancer drugs to see which ones kill the cancer cells. Scientists are investigating the usefulness of approaches that utilize this technique, but current evidence does not justify the routine use of this research tool for patients. At this time, in vitro drug sensitivity tests are too cumbersome and expensive for general practice. Further, they do not appear to provide additional benefit over an experienced clinician's judgment and knowledge of the effectiveness of available anticancer agents.

Various experimental chemosensitivity techniques have been studied. Two of these approaches, the human tumor colony-forming assay and the cell sensitivity assay, appear promising, although they are not yet practical as a routine undertaking.

In the human tumor colony-forming assay (also called the clonogenic assay), cells taken from a patient's cancer are placed in test tubes and exposed to anticancer drugs. After a short period of time, the drug is removed, and the cells are placed in other laboratory containers to see whether they will grow. Little or no growth of the cancer cells indicates that the test drug has been effective. Although studies show that this technique has some value in predicting drug sensitivity, it has several disadvantages that make it impractical for routine use. For example, the results of this test may take from 2 to 3 weeks to obtain, and they are difficult to interpret. In addition, it is often hard to grow cells from certain cancers, such as lung, breast, and colon cancers. It is also difficult to test drugs that must interact with chemicals in the body in order to be effective. Further, it is not yet possible to duplicate drug concentrations and duration of exposure within the body.

The second technique is to grow cells from human tumor specimens first and then test them for drug sensitivity. This approach has many of the same problems as the clonogenic assay and, although it appears promising in predicting sensitivity of nonsmall cell lung cancer, it is not yet practical as a routine undertaking.

Biochemical tests based on how anticancer drugs act within the body also are being evaluated for their ability to predict drug sensitivity. However, additional studies are needed to determine their value in routine treatment of cancer patients.