Success of Anticancer Drugs

Various forms of cancer exhibit a broad spectrum of response to antineoplastic medications. Some forms of cancer (choriocarcinoma, Wilms tumor) can be cured in more than 90 percent of affected patients. In other neoplastic disorders, chemotherapy may not cure the disease but may succeed in mediating remission and prolonging survival in a large patient percentage. Of course, other factors such as early detection and the concomitant use of other interventions (surgery, radiation) will greatly influence the success of chemotherapy drugs. 

However, several types of cancer do not respond well to treatment. For example, the majority of metastatic cancers cannot be cured by current chemotherapeutic methods or by any other type of treatment.11 In addition, some of the most common forms of adult neoplastic disease are difficult to treat by using anticancer drugs. As indicated in Table 36-9, the number of deaths associated with colorectal, prostate, and breast cancer is unacceptably high, and the mortality rate for lung cancer and pancreatic cancer is well over 90 percent in both men and women. 

Exactly why some forms of cancer are more difficult to treat pharmacologically than others remains unclear. Differences in the biochemistry, genetics, and location of certain cancer cells may make them less sensitive to the toxic effects of anticancer drugs.6 Resistance to anticancer drugs 

As indicated previously, certain cancers do not respond well to cancer chemotherapy. A primary reason is that cancers may develop resistance to a broad range of chemotherapeutic agents (multiple drug resistance), thus rendering these drugs ineffective in treating the cancer.9,74 

Cancers can become resistant to drugs through several different mechanisms. One common mechanism occurs when the cancer cell synthesizes a glycoprotein that acts as a drug efflux pump.15,74 The glycoprotein pump is inserted into the cancer cell s membrane and effectively expels different types of anticancer drugs from the cancer cell. Thus, cancer chemotherapeutic agents are ineffective because they are removed from the cell before they have a chance to exert cytotoxic effects. 

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