NCIt definition : Mechanisms, functions, activities, or processes exhibited by tumors or pathogens to
withstand previously toxic drugs.;
Alternative definition : NCI-GLOSS: The failure of cancer cells, viruses, or bacteria to respond to a drug
used to kill or weaken them. The cells, viruses, or bacteria may be resistant to the
drug at the beginning of treatment, or may become resistant after being exposed to
the drug.;