Dear Readers:

Here is an update on a relatively new type of cancer affecting cats. It is vaccine-induced sarcoma.

Thanks to my colleague in Houston, Dr. Kevin Hahn, for providing me with the protocol he uses.

Feline injection-site sarcomas are solid cancerous tumors that arise at the site of a prior injection, most commonly a vaccination (rabies and feline leukemia virus).

The time between vaccination and tumor development can be as short as several months. The exact cause is unknown, but the preservative (aluminum hydroxide) contained in many vaccines has been suggested as a possible cause.

It appears that cats that are genetically predisposed to cancer can develop tumors following the chronic inflammation that occurs at the site of an injection.

Any lumps that are present on your pet should always be investigated. Inflammatory lumps that arise following vaccination should be watched closely. If they do not disappear within several weeks, a biopsy will reveal a definitive diagnosis.

However, because of the aggressive invasiveness of this tumor, it may be difficult to remove all the cancer.

Following biopsy, if the diagnosis is cancer (fibrosarcoma), several recommendations can be made.

First, follow-up therapy with radiation and chemotherapy has shown the most promise in curing the cancer or at least in keeping the cat in remission as long as possible. If the tumor recurs, additional surgery and treatment may be needed.

Changing the diet to a cancer diet (high in protein and omega-3 fatty acids and low in carbohydrates) and administering supplements to support the immune system (various herbs or homeopathics) are also important in treating the cat.

Only vaccines that are absolutely needed should be administered.

The use of blood titer (antibody) tests can help guide your doctor in determining which vaccines your pet might need. If vaccines are given, administering homeopathic Thuja might minimize vaccine reactions. Pet owners should carefully monitor injection sites to make sure any inflammatory reactions disappear.

There have been a few cases reported of dogs developing similar tumors following injections. In the August issue of a noted pathology journal, 10 samples of canine tumors from known injection sites showed the same pathology as feline fibrosarcoma tumors. Since the most common injection is vaccination, I believe this further indicates that we use common sense when deciding which pets require immunizations.

— Dr. Shawn P. Messonnier, author of the “Natural Health Bible for Dogs & Cats” (Prima, $24.95) is a veterinarian and pet care advocate.