UC-Davis studies malignant melanoma in dogs

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Aug 01, 2006

DAVIS, CALIF. — Dr. Michael Kent, an investigator at the University of California-Davis, is exploring different drugs to help fight canine malignant melanoma.

The Morris Animal Foundation is providing a portion of the grant money necessary to conduct the research, which could unveil a way to make these types of tumors less resistant to treatment.

The fatality rate of this cancer is very high despite aggressive treatment with surgery, radiation therapy and chemotherapy.

"This type of cancer is fairly common and often fatal," Kent says. "We are testing drugs in cell lines developed from dogs with oral melanomas in combination with radiation."

The tumors often are found in dogs' mouths, nail beds or skin.

Seizures and difficulty breathing can occur if the cancer spreads.

Cancer of the oral cavity accounts for 6 percent of canine tumors, making it the fourth most-common neoplasm in dogs, and malignant melanoma accounts for 30-40 percent of all oral lesions, Kent says.

"Similar to the disease in people, malignant canine melanoma is a highly metastatic tumor with many patients not surviving more than six months post diagnosis," he adds. "Surgery in the oral cavity for melanomas often requires extensive procedures, such as maxillectomy, mandibulectomy and/or orbitectomy and is rarely used for lesions located in the caudal portion of the mouth due to a substantial increase in morbidity.

Even with radical surgical procedures, local recurrence rate ranges from 25-43 percent. With radiation therapy, up to 83 percent of dogs having a complete or partial response, the time to regrowth or metastasis is often short lived with reported overall survival times of seven months.

Kent says if this work is successful, the next step will be to try these drugs in combination with radiation therapy.

The foundation is sponsoring the research for two years. Kent, in his sixth month of research, hopes the end result will improve the efficacy of treatment and lead to better tumor control.