Compositions of matter for treating cancer patients are used to prevent or limit cardiotoxicity during or after treatment with anthracycline drugs, and to prevent or lower resistance to anthracycline drugs, both of which are believed to be caused by the human enzyme carbonyl reductase. Preferred embodiments comprise a pharmaceutical composition comprising compounds having halogenated (or pseudo-halogenated) aryl groups, preferably halogenated (or pseudo-halogenated) arylcyanooximes or phenylcyanooximes and derivatives or analogs thereof, including those comprising —CL or —F, or other substituents on an aryl/phenyl ring. The preferred composition of arylcyanooxime(s) may be administered in a pharmaceutical composition also comprising at least one anthracycline compound, or may be administered separately from the at least one anthracycline compound.