Few things strike quite as much fear in the hearts of pet lovers as a cancer diagnosis in their beloved companion. One reader wrote to ask me about a possible new treatment for oral melanoma, which had just been diagnosed in her dog:
Q: My Golden Retriever had a swelling in his mouth, and it has been diagnosed as melanoma. I understand there is a vaccine for the disease. What can you tell me about this type of cancer and its treatment?
A: Melanoma is a common oral tumor in dogs. We see it more often in males than females, and certain breeds seem to be affected more often, including goldens, chow chows, cocker spaniels, Gordon setters and Scottish terriers.
This type of tumor invades the bone of the jaw and is likely to spread elsewhere in the body, especially to the lungs and lymph nodes. Surgery and radiation therapy can help to manage localized tumors, but once melanoma starts to spread (metastasize), it tends to be resistant to chemotherapy.
A DNA-based vaccine has been developed that may help control oral melanomas in some dogs. It’s approved by the Department of Agriculture for treatment of “locally controlled” stage 2 or 3 oral malignant melanoma in dogs. That means the tumor and any metastasis to the lymph nodes has been reduced to undetectable levels through surgery and radiation treatment before the vaccine is administered. Dogs with locally controlled melanoma who receive the vaccine can have good survival times.
However, according to my colleague Michael Childress, DVM, an internal medicine specialist at Purdue University, a recent study documented no significant improvement in survival for dogs treated with the vaccine, called Oncept, compared to dogs who did not receive the vaccine. He does note, though, that this study had certain limitations. In his observations, the vaccine “seems to afford significant benefit for some dogs, but limited benefit for many others.” It may be, he adds, that certain tumor-related factors affect response to the vaccine, but these are as yet unknown.
Oncept has a good safety record. Common side effects tend to be reactions or hematomas at the injection site.
Read more, including about summer books for pet lovers, in this week’s Pet Connection!