In our article "Intracavitary and intralesional chemotherapy in dogs and cats" (March 2013), we presented literature reports of using preparations containing doxorubicin and mitoxantrone for control of cavity-based cancers (see the full text of this article at dvm360.com/ChemoAlternatives) . These drugs are substrates of the P-glycoprotein pumps of the MDR1 gene.
In the hard-copy version of the article, photographs of collies were included for artistic reasons by the editors. The authors would like to point out to readers that these dogs, and certain other breeds, frequently have mutated MDR1 genes that cause them to handle some chemotherapy drugs, including doxorubicin and probably mitoxantrone, differently than dogs without the MDR1 mutation. For these breeds, standard dosages of these drugs could prove fatal. Veterinarians should consult with an oncologist before using chemotherapy drugs in a breed with high potential for these mutations.
Lisa Gorman, DVM
University of Minnesota Veterinary Medical Center
St. Paul, Minn.
Jeffrey N. Bryan, DVM, MS, PhD, DACVIM (oncology)
Department of Veterinary Medicine and Surgery
College of Veterinary Medicine
University of Missouri, Columbia, Mo.