Resistance to chemotherapy is a major source of failure in cancer treatment. A large number of cancers are intrinsically resistant to cytostatic agents; others initially respond to treatment, but subsequently develop a resistance to the drugs being used. Of the human solid malignancies, small cell lung carcinomas (SCLCs) are among the most chemosensitive and radiosensitive tumors, with most of them responding to initial therapy. However, the majority not only will recur but will remain largely refractory to further treatment. Most non-small cell lung carcinomas (NSCLCs) are primarily resistant to therapy; it is rare to obtain a complete response.
