FELINE FIBROSARCOMA
Philip J. Bergman DVM, MS, PhD; Diplomate ACVIM, Oncology
Head, Donaldson-Atwood Cancer Clinic; The Animal Medical Ctr.
510 East 62nd St, NY, NY 10021.

     Vaccination has generally been considered to be a benign procedure in
veterinary medicine. Unfortunately, soft tissue sarcoma development subsequent
to vaccination (vaccine-associated sarcoma; VAS) in cats has dramatically
changed this view within our profession over the last ten years.

     The vaccines generally associated with this disease to date have been the
adjuvanted rabies and feline leukemia virus vaccines, however, association with
non-adjuvanted FVRC-P vaccines have 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 non-adjuvanted
vaccines are likely a step in the right direction for the prevention of this
disease, and we eagerly await longer-term results on the incidence of tumors
with these vaccines.

     Currently, VAFSTF (Vaccine-Associated fibrosarcoma Task Force)in concert
with the AVMA and AAFP recommend that: 1)use of vaccines packaged in
single-dose vials is strongly encouraged, 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 is
entered into the permanent medical record, 4) vaccines limited to panleukopenia,
herpesvirus and calicivirus should beadministered on the right shoulder, 5)
rabies vaccines should be administered as distally as possible on the right rear
limb, 6) feline  leukemia virus vaccines should 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 you suspect you are dealing with a VAS in a cat,the appropriate staging
diagnostics should include full physical examination, bloodwork/urinalysis,
retroviral 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 sarcoma virus-associated sarcoma. Radiography for the
evaluation of metastasis is performed since it appears that approximately 5% of
cats with VAS have metastasis at presentation,whereas approximately 20-25% have
metastasis at necropsy. Confirmation of the suspected diagnosis should be
performed by obtaining an incisional biopsy with a Tru-Cut biopsy instrument (or
similar incisional biopsy instrument), or small wedge biopsy. 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 appears appropriate since patients with VAS
of the distal limbs can undergo radical surgical extirpation via amputation.
Unfortunately, even with aggressive surgery alone, relatively few cats with VAS
are cured. Due to poor cure rates with surgery alone, the additional use of
adjuvant radiation therapy and/or chemotherapy 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 prior to radical
surgery, or perform radical surgery and then post-operative radiation therapy.
However, the combination of radical surgery and radiation therapy in recent
studies appears to have a median survival time of 600-800 days, suggesting that
additional therapies is 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
50-60% response rate. Feline non-VAS would be expected to have a 10-15%
response rate to these forms of chemotherapy, thereby suggesting that feline VAS
is a remarkably different beast 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 extremely
immature, but preliminary indications suggest tri-modality therapy will very
likely be the preferred therapy for this extremely malignant tumor.

     Through the support of VAFSTF, there are currently a number of research
studies ongoing throughout the country to elucidate the etiopathogenesis,
epidemiology, treatment and prevention of this disease (reader is referred to
www.avma.org and the VAFSTF link). It is easy to see that even with aggressive
therapies, we many times lose the battle against this remarkable tumor. The key
to this disease is a better understanding of what causes this tumor, so that we
may determine ways to vaccinate our feline friends without inducing extremely
malignant tumors. We eagerly await the results of currently funded
VAFSTF-sponsored studies as well as ongoing research studies by the vaccine
manufacturers to rid this disease from our profession.

References:
1. Hershey AE, Sorenmo KU, Hendrick MJ et al. Prognosis for presumed feline
vaccine-associated sarcoma after excision: 61 cases (1986-1996). J Am Vet Med
Asoc 2000;216:58-61.
2. Vaccine-Associated Feline Sarcoma Task Force guidelines. Diagnosis and
treatment of suspected sarcomas. J Am Vet Med Assoc 1999;214:1745.
3. Couto CG, Macy DW. Review of treatment options for vaccine-associated feline
sarcoma. J Am Vet Med Assoc 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.