Cats: Vaccine-Related Sarcomas

This was a relatively short article and one topic, thankfully, that I have never experienced.  Since many of my cats do come from unknown backgrounds, I do suspect that some are at risk, but so far, so good. 

Recent Advances in the Treatment of Vaccine-Sarcomas, by Gregory K. Ogilvie, DVM
p 525-533 in Vol 31, No 3, Vet. Cl. of NA: Small Animal Practice, May 2001...

The article focuses on the diagnosis and treatment of the sarcoma and not on the fact that vaccines seem to cause sarcomas.  The latter is assumed by the article. The article doesn't mention, but from other sources the sarcomas are linked primarily to FeLV and rabies vaccines.

Physical exam -- The sarcoma appears as a lump or thickening either at the injection site or, interestingly, on the underside of the cat (migration of vaccine agent).  The lump can appear from days to years afterwards. This timing, days to years, is a bit scary since I do not know the vaccine history of many of my cats.

Evaluation -- The first step is a needle biopsy to confirm that it is a sarcoma.  The next step is xrays to determine if it has metastasized.  Enlarged lymph nodes may need to be biopsied.

Treatment of small tumors -- The recommendation is for a 2cm cuff around the tumor and 1 skin layer deeper.  2cm on both sides is HUGE!  The author mentions the inconclusiveness of both chemotherapy and radiation therapy, and from other sources, this does not seem to have changed significantly in recent years.

Treatment of large tumors -- The author recommends surgical reduction of the tumor followed by radiation treatment.

Metastatic sarcomas -- Chemotherapy seems to be the solution but at the time of writing there was no clear recommendations.

Patient Management -- The author stresses the need to give the client pain meds, anti-nausea meds, and appetite stimulants to help the cat.  Also, the client should be given written instructions and educational material because owners often are very upset when told their cat has cancer.

Prognosis -- For small, non-metastatic tumors, the prognosis is good.  Otherwise, the outcome is usually not good as the tumor recurs.  Who does the surgery and how extensive it was drastically influences the outcome:

"The median time of tumor control was 94 days.  Median tumor control for tumors treated with excision performed at a referral institution (274 days) was significantly longer than that for tumors excised by a referring veterinarian (66 days).  A radical first excision yielded significantly longer median tumor control (325 days) than did a marginal first excision (79 days)..... Few cats (13.8%) receiving only surgical treatment had long-term (>2 years) survival, suggesting that radiation and chemotherapy are highly indicated as adjunctive therapies."  And this is an interesting statement about radiation and chemotherapy given what the author said previously about the inconclusiveness.

These vaccine-related sarcomas are the reason the new vaccine protocols recommend vaccinating for rabies and FeLV in the legs or even tail -- those parts can be amputated to save the cat from the sarcoma.  To me this is very drastic and makes me ever so grateful that I don't have to vaccinate for rabies of FeLV.