Clinical Rounds: Battling a Labrador's oral malignant melanoma - Veterinary Medicine
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Clinical Rounds: Battling a Labrador's oral malignant melanoma
After a referring veterinarian diagnosed this deadly neoplasm in a senior Labrador retriever, this team of experts stepped in to help extend the dog's life with targeted treatment. What can you learn from their approach to help your patients?


VETERINARY MEDICINE


MEDICAL ONCOLOGY PERSPECTIVE

Olya A. Smrkovski, DVM, DACVIM (oncology)


Olya A. Smrkovski, DVM, DACVIM (oncology)
Metastatic disease is the principal cause of death in most dogs with oral malignant melanoma, especially those with good local tumor control.19 Chemotherapeutics with reported activity against oral malignant melanoma include carboplatin, cisplatin with piroxicam, dacarbazine, doxorubicin, and melphalan, but platinum drugs have the most activity.20-25 The overall response rate to carboplatin is 28%, and the reported response rate to a cisplatin-piroxicam combination is 18%.22,24

Administration of adjuvant chemotherapy has failed to significantly improve overall survival in dogs with oral malignant melanoma.19-25 However, it continues to play a role in the management of this malignancy. At the University of Tennessee Veterinary Medical Center, chemotherapy is used in patients that develop progressive disease after the four initial treatments of the canine melanoma vaccine or when the vaccine is cost-prohibitive to owners. Metronomic (continuous, low-dose oral chemotherapy aimed at inhibiting tumor angiogenesis) is being increasingly used to treat solid tumors.26-28 It was not used in this case but can be considered in the future as more reports of its efficacy emerge.

Malignant melanoma is a highly immunogenic tumor. Of the multiple immunotherapeutic approaches investigated to date, Oncept, a xenogeneic DNA vaccine containing human tyrosinase (HuTyr) has shown the most promise. In one study, administration of this vaccine to 58 dogs with stage II and III oral malignant melanoma resulted in significant improvement in survival time compared with historical controls.29

The vaccine was licensed by the USDA in 2009 and is administered with a needle-free device every other week for a total of four treatments.30 Subsequent boosters at six-month intervals are recommended, provided there is no evidence of tumor progression.30 Oncept has not been associated with any systemic side effects; local side effects such as bruising and hematoma formation at the injection site are rare.29 Oncept is currently licensed to veterinary specialists boarded in either oncology or internal medicine.


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Source: VETERINARY MEDICINE,
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