MODIFIED WIDE LOCAL EXCISION FOR VACCINE ASSOCIATED SOFT TISSUE SARCOMAS IN CATS

Published in "Veterinary Surgery", the journal of the American College of Veterinary Surgeons

Volume 29, #5 September/October 2000

Charles A. Kuntz, DVM, MS

Diplomate ACVS

Introduction: Vaccine associated soft tissue sarcomas (VASTS) recur following surgery at a higher rate than other soft tissue sarcomas in cats and dogs. They metastasize at a rate comparable to other soft tissue sarcomas (20%). This suggests that alternatives to conventional wide local surgical resection (2-3 cm in all directions and a single fascial plane deep) must be sought. Radiation therapy is offered as an adjunct to surgery but is expensive, is offered at a few referral centers, and requires multiple anesthetic episodes in cats which may be poor anesthetic candidates. Modified wide local excision (5 cm in all directions and 2 muscle planes deep) may offer improved regional control.

Materials and methods: Records of cats with VASTS treated with modified wide local excision were reviewed for signalment, location of tumor, number of previous surgeries, histologic description of excised tumor, and their effects on metastasis, local recurrence and survival. All cats had modified wide local excision of their tumors by the primary author, defined as 5 cm margins laterally around any visible or palpable tumor or surgical scar and at least 2 muscle planes deep to any palpable tumor or surgical scar. All structures falling within this perimeter were excised en bloc. Surgical margins were marked with India ink and evaluated for completeness of surgical excision. Analgesia in all cats included lidocaine/bupivicaine splash block (one to three mls/cat), morphine (0.1 mg/Kg Q 4-6 hours), and either a fentanyl patch (25 ug/hr in cats weighing greater than 4 kg) or codeine elixir (0.5 mg/Kg QID in cats weighing less than 4 Kg) for a duration of 5 days after surgery.

Results: Twenty-four cats had modified wide local excisions of VASTS. Thirteen were spayed females and 11 were neutered males. Twenty-two were mixed breeds and two were pure breeds. Ages ranged from six to 17 years with a median of 11 years. Twenty-two had tumor tissue identified in the excised specimen for histological evaluation. One had a grade I tumor, six had grade II tumors, 15 had grade III tumors. Nineteen had fibrosarcomas, two had malignant fibrous histocytomas and one had an osteosarcoma. All had primary closure of their surgical wounds and none required the use of synthetic meshes or skin grafts. One cat developed a pneumothorax the evening following surgery and this was successfully treated using a chest tube. Two cats had chemotherapy and none had radiation therapy. Twenty-three of 24 cats (96%) had complete surgical margins. One cat died of metastasis. No cats had local recurrence. Follow-up ranged 2 to 433 days after surgery. Because absence of recurrence, and the low frequency of metastasis and tumor related death, prognostic factors could not be determined.

Discussion: While the data needs to mature before conclusions can be drawn, the lack of local recurrence in this patient set compares favorably with other reviews of surgical treatment with or without radiation therapy for vaccine associated tumors.

Special addendum shared with us by Dr. Kuntz:

Since this abstract, I have operated on 40 cats with VAS in two years. I have had a single recurrence in two years and a single cat with incomplete margins. While I recommend surgery and radiation therapy and chemotherapy for clients who can afford it, realistically, many have to stop at the surgery (about 1500-1600 dollars at my practice). I figure that if we have one shot at it, I am going to go for the gusto. I get 5 cm in all directions. I have had only one cat die of complications associated with this surgery.

Charles A. Kuntz, DVM, MS
Diplomate ACVS
The Regional Veterinary Referral Center
6651-F Backlick Rd.
Springfield, VA 22150
Phone: (703) 451-8900
Fax: (703) 451-3343  

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