Prognosis for Presumed Feline Vaccine-Associated Sarcoma after Excision: 61 Cases (1986-1996)
J Am Vet Med Assoc 216[1]:58-61 Jan 1'00 Retrospective Study 14 Refs
* A. Elizabeth Hershey, DVM; Karin U. Sorenmo, CMV, DACVIM; Mattie J. Hendrick, VMD, DACVP; Frances S. Shofer, PhD; David M. Vail, DVM, DACVIM
* Dept. of Medical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706
OBJECTIVE: To evaluate time to first recurrence (TFR) and overall survival in cats with presumed vaccine-associated sarcomas (VAS) treated with excision.
DESIGN: Retrospective study.
ANIMALS: 61 cats with presumed VAS.
PROCEDURE: Medical records of cats that received excision as the only initial treatment for presumed VAS were reviewed to evaluate prognosis. Overall survival curves and TFR were determined.
RESULTS: Median TFR was 94 days. Median TFR 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). Radical first excision yielded significantly longer median TFR (325 days) than did marginal first excision (79 days). Cats with tumors located on the limbs had longer median TFR (325 days) than cats with tumors located in other sites (66 days). Median overall survival time was 576 days. Significant differences in survival times between groups were not detected. Few cats (13.8%) receiving only surgical treatment had long-term (> 2 years) survival.
CONCLUSIONS & CLINICAL RELEVANCE: Radical first excision of presumed VAS is essential for extended TFR. Current recommendations for vaccination of the distal portions of the extremities are appropriate, because this practice permits radical excision of tumors (amputation) that develop at vaccination sites; however, surgery alone is seldom curative.
A SUMMARY of article
There has been an increase in incidence of fibrosarcomas developing at typical vaccination sites. These vaccine - related sarcomas (VAS) are characterized by an intense inflammatory infiltrate composed of lymphocytes and macrophages. The proposed mechanism for the formation of sarcomas is that, in genetically susceptible cats, resident fibroblasts undergo neoplastic transformation due to persistent inflammation secondary to vaccine adjuvants. Aluminum adjuvant particles have been found histologically in VAS but it is unknown if they induce the neoplastic transformation or are markers of the neoplastic process.
There is currently little data available as to the efficacy of treatment of VAS. Previous studies have indicated that surgical excision with wide margins results in extended tumor free interval and survival times. In cases of tumors on limbs, amputation was superior to wide excision.
Purpose
determine the prognosis in cats when treated with surgical excision alone
evaluate the effect of primary tumor location
evaluate the effect of marginal, wide and radical surgery
The above factors were all evaluated in relation to the time of first recurrence (TFR)
Population studied
Cases were selected from records of the Veterinary Hospital of the University of Pennsylvania (VHUP) or the University of Wisconsin - Madison Veterinary Medical Teaching Hospital (UWVMTH) from 1986 through 1996. Tumors had been confirmed histologically as sarcomas and cats were included in this study if they had been treated with surgical excision at least once and if follow up information was available. Sarcomas which occurred in areas not associated with vaccination were excluded from the study. Overall, 61 cats were included in the study. Of the 61 cats, 25 also underwent chemo or radiotherapy.
Procedures
Diagnostic work up and clinical staging included: Thoracic or abdominal radiographs, CBC and chemistry profile, viral screening tests, and abdominal ultrasound. Results of chest radiographs were considered the most important criteria for metastasis.
Definitions
Classification of surgical excision:
Marginal: excision with margins < 3 cm in width
Wide: larger excisions of previous surgical excisions or tumors with margins >3 cm
Radical: procedures such as amputation, hemipelvectomy, partial scapulectomy and removal of dorsal spinous processes.
Time of recurrence (TFR) is defined as time of first surgery to recurrence of tumor.
Survival is defined as days from first excision until death.
Results
The following is a brief summary of results; readers should consult full text of article for additional details and graphs.
Signalment
mean and median age of cats was 9 years
54% were castrated males; 46% were spayed females
predominant breed was DSH; DLH (12%) Persian (3%) Siamese (3%)
Metastasis
Overall rate of metastasis was 22.5% (n=9)
3 of the 9 had evidence of metastasis at initial examination at referral
6 of the 9 developed metastasis after or during treatment
8 of the 9 cats had undergone multiple surgeries prior to development of metastasis
Rate if metastasis differed between VHUP (28%) and UWVMTH (14%)
Metastatic lesions included pulmonary lesions, lymph nodes and skin lesions
Time of metastasis ranged from 31- 405 days (medium 265)
Serologic tests (40 of 61 cats were serologically tested for viruses)
1 cat tested positive for FeLV and had multiple recurrences and subsequent pulmonary metastasis
7 cats tested negative for FIV virus
Duration of clinical signs (time between tumor detection and first excision) was recorded in 45 of 61 cats
mean: 2 months
median: 1 month
range: 2 days to 8 months
Primary tumor locations
flank 36%
proximal hind limb 18%
lumbar area 16%
Type of first excision
80% of cats had marginal first excisions
7% had wide first excisions
13% had radical first excisions (amputation)
TFR (time to first recurrence)
mean = 94 days
only 11% treated with excision alone had TFR > 1 year (4 of these cats had amputation; 3 had wide truncal excisions)
TFR was significantly longer when tumors were treated at the referral institution vs. the referring veterinarian
Marginal first excisions: mean TFR = 66 days
Wide first excisions: mean TFR = 419 days
Radical first excisions: mean TFR = 325 days
TFR in cats with radical first excisions was significantly longer than in the combined wide and marginal first excision group
Survival time
Median survival time for all 61 cats was 576 days
Most cats had multiple surgeries and/or additional therapies
Only 5 of 36 cats which did not receive multiple therapies were long term survivors (>1300 days) and 4 of these 5 cats had hind limb amputations. 1 of the 4 cats was euthanized at 1349 days for tumor recurrence at the amputation site
Significant differences in survival was not detected in cats which received surgery and other treatments and cats treated with surgery alone
There were no significant differences in survival:
in cats treated with marginal vs. radical excision;
in cats treated by referring veterinarians and those treated at the referral institution or
between appendicular tumors and other locations.
Discussion
Initial treatment of VAS by aggressive, radical surgery appears to increase the TFR in cats. Those cats treated with radical first excisions had a significantly longer TFR than cats treated with marginal excisions. Wide first excision is also superior to marginal first incision - 3 of 4 cats with truncal sarcomas treated with wide excision had TFR> 1 year.
Location of the tumor affects survival - those on the limbs had significantly longer TFR - this may be because limb tumors could be treated with amputation whereas complete excision of tumors of the trunk is difficult.
Because survival of cats is affected by various owner factors such as decisions of additional treatments, TFR seems be to a better marker of surgical efficacy. Median survival for all cats was 576 days, which is similar to another study in which cats had a median survival time of 600 days. Additional treatments do contribute to longer survival times and cats can have a prolonged period of quality life.
Metastatic rate in this study was 22.4% for all cats but there was a difference in the rate of metastasis between the 2 referral institutions: 14% at UWVMTH vs. 28% at VHUP. This may be because cats referred to UWVMTH more commonly received systemic treatments but the effectiveness of the addition of chemotherapy to surgery as treatment of VAS is inconclusive.
Conclusion
The authors conclude that radical initial excision of VAS is the best way to increase TFR and that current vaccination site recommendation (in the distal limb) is most appropriate because sarcomas at this location can best be treated with amputation. However, the authors point out that surgery alone is seldom curative; these tumors have high metastatic rates and may behave more aggressively than originally thought. Few cats were long term survivors.
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