Guest Editorial: Oncology
Philip J. Bergman, DVM, MS, PhD
Diplomate, ACVIM (Oncology)
Head, Donaldson-Atwood Cancer Clinic
The Animal Medical Center
New York, NY

Vaccination has generally been considered a benign procedure in veterinary medicine. Unfortunately, however, soft tissue sarcoma development in cats subsequent to their being vaccinated (vaccine-associated sarcoma [VAS]) has dramatically changed this view within our profession over the last 10 years. Thanks to the creative thought of the American Animal Hospital Association (AAHA) and the American Association of Feline Practitioners (AAFP), the Vaccine-Associated Feline Sarcoma Task Force (VAFSTF) was born over 5 years ago and has been steadfastly dedicated to eradicating this disease by facilitating investigations into the disease's epidemiological aspects, etiopathogenesis, treatment, and prevention. Over the past few years, there has been an increase in the amount of literature available concerning the diagnosis and treatment of this disease; this article is meant to be a review of this literature and a mechanism to provide evidence-based rationale for the treatment of this devastating disorder. ^1-5

To date, the vaccines generally associated with this disease have been the adjuvanted rabies and feline leukemia virus (FeLV) vaccines; however, an association with nonadjuvanted feline viral rhinotracheitis (herpesvirus)-calicivirus-panleukopenia (FVR-C-P) vaccines has been occasionally reported.

The potential role of inflammation as a necessary antecedent to the development of this disease has been previously published and seems highly plausible based on the aforementioned association with adjuvanted vaccinations. Newer nonadjuvanted vaccines are likely a step in the right direction for the prevention of this disease, and we eagerly await greater long-term results on the incidence of tumors with these vaccines.

Currently, the VAFSTF, together with the American Veterinary Medical Association (AVMA) and the AAFP, recommends that (1) we use vaccines packaged in single-dose vials, (2) occurrences of VAS or other adverse reactions be reported to the vaccine manufacturer and the United States Pharmacopoeia (USP; 1-800-4-USP-PRN), (3) vaccination protocols be standardized within practices so that location, type, manufacturer, and serial number are entered into the permanent medical record, (4) vaccines limited to FVR-C-P be administered on the right shoulder, (5) rabies vaccines be administered as distally as possible on the right rear limb, (6) feline leukemia virus vaccines be administered as distally as possible on the left rear limb, and (7) injection sites of all other medications be recorded in the permanent medical record. This information can also be accessed at www.avma.org.

If one suspects that one is dealing with VAS in a cat, the appropriate staging diagnostics should include a full physical examination, blood work/urinalysis, retro-viral testing, and 3-view chest radiographs. Retroviral testing is recommended to ensure that FeLV is not acting as a helper virus for the production of a feline virus-associated sarcoma. Radiography, for the evaluation of metastasis, is performed because it appears that approximately 5% of cats with VAS have metastasis at presentation, whereas approximately 20% to 25% have metastasis at necropsy. Confirmation of the suspected diagnosis should be performed by obtaining an incisional needle biopsy specimen or small wedge biopsy specimen. The tumor should not be removed until a complete diagnosis is made and a consultation with an oncologist or surgeon has been performed.

Recent studies document that radical first excision of VAS is essential for an extended period of time without recurrence. In addition, recent studies also document that the practice of vaccination of the distal portions of the limbs for rabies and/or FeLV vaccinations appear appropriate because patients with VAS of the distal limbs can undergo radical surgical extirpation via amputation. Unfortunately, even with aggressive surgery, relatively few cats with VAS are cured. Because of poor cure rates with surgery as a single means of therapy, the additional use of adjuvant radiation therapy or chemotherapy, or both, has been under investigation at multiple veterinary cancer centers for the last few years. It is presently unknown whether it is better to perform radiation therapy before radical surgery, or to perform radical surgery and then postoperative radiation therapy. However, the combination of radical surgery and radiation therapy in recent studies appears to produce a median survival time of 600 to 800 days, suggesting that additional therapies are worthwhile in the treatment of this disease.

Similarly, the use of chemotherapy has been reported by multiple investigators to have efficacy against feline VAS. When given to cats with grossly palpable VAS, carboplatin or a combination of doxorubicin and cyclophosphamide resulted in a 50% to 60% response rate. Feline non-VAS would be expected to have a 10% to 15% response rate to these forms of chemotherapy, thereby suggesting that feline VAS is a remarkably different tumor than non-VAS.

The use of radical surgery, radiation therapy, and chemotherapy as tri-modality therapy in feline VAS is likely the best form of therapy for cats with VAS based on recent abstracts from the Veterinary Cancer Society. Unfortunately, these data are premature for confident conclusions, but preliminary indications suggest tri-modality therapy will very likely be the preferred therapy for this extremely malignant tumor.

Through the support of the VAFSTF, there are currently a number of research studies ongoing throughout the country aiming to elucidate the etiopathogenesis, epidemiological aspects, treatment, and prevention of this disease (refer to www.avma.org and the VAFSTF link). It is easy to see that even with aggressive therapies, we often lose the battle against this remarkable disorder. The key to this disease is a better understanding of what causes it, so that we may determine ways to vaccinate our feline patients without inducing extremely malignant tumors. We eagerly await the results of currently funded VAFSTF-sponsored studies, as well as those of ongoing research studies by the vaccine manufacturers so that this disease is not a threat in the future.

             3. Couto CG, Macy DW. Review of treatment options for vaccine-associated feline sarcoma. J Am Vet Med Asscc   1998;
             213:1426-1427.  

             4. Bergman PJ. Etiology of feline vaccine-associated sarcomas: History and update. J Am Vet Med Assoc 1998;     213:1424-1425

             5. Kobayashi T, Hauck ML, Price GS, et al. A retrospective analysis of 189 cats evaluated for feline vaccine site sarcoma from 1985 to
             1998. Vet Cancer Soc Proc 1999; 23.

Copyright © 2000 by W. B. Saunders.   This material may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means without the prior written permission of the publisher.