Prolonged Remission and Survival Time in Cats With Injection-Site Associated Sarcomas Using Pre-Operative Radiation and Doxorubicin Protocol: 61 Cases (1988-2000)

G.K. King, D.V.M. , D.F. Harris, D.V. M. , H. Hottinger, D.V.M. , K.P. Freeman, D.V.M. ,
K.A. Hahn, D.V.M. , Ph.D. Gulf Coast Veterinary Oncology, Houston, TX 77027

Objective:  To Compare the use of pre-operative radiation and doxorubicin versus pre-operative radiation along for treatment of cats with injection-site associated sarcomas.

Methods:  In this retrospective analysis, medical records of cats referred to Gulf Coast Veterinary Oncology with histologically confirmed injection-site sarcomas from January 1988 to January 2000 were evaluated.  Cats were included in the study if they had grossly evident and visible disease in a known injection-site sarcoma associated location (i.e., interscapular) without metastases.  Cats with prior tumor resection with macroscopic recurrence were not excluded.  All cats were clinically staged and computed tomography (CT) scans were performed to assist development of plans for radiation therapy.  Megavoltage radiation therapy was administered during a 7-week period, on a Monday, Wednesday, Friday schedule for a total delivered dose of 60-62 Gy.  Chemotherapy, if given, was administered beginning on the day of the second radiation fraction.  Doxorubicin (1 mg/kg, IV) was given every 3 weeks until 5 doses had been administered.  Six weeks following the completion of radiation therapy and 1 week following the 5th doxorubicin treatment, macroscopic tumor resection was performed.  Time to first recurrence was defined as number of days from completion of surgical resection until recurrence of the tumor.  Survival time was defined as number of days from surgical resection until death.  Complete staging was performed every 3 months after completion of treatment.  Curves for time to first recurrence and survival were generated by use of Kaplan-Meier product limit method.  Data were censored if cats were free of disease, lost to follow-up, or died of disease unrelated to the sarcoma diagnosis.  Differences between curves were analyzed by applying the log rank test.  Multivariate analysis was performed  to determine the possible influence of pre-operative tumor size, tumor location, and other patient-related and treatment-related variables.  Significance was established at p<0.05.

Results: Sixty-one cats were included in the study.  Thirty-one cats had radiation and surgery alone, 30 cats had radiation, doxorubicin and surgery combined.  Cats whose protocol included doxorubicin had a significantly longer remission time (median 360 days; range, 54 to 1,347 days) than those cats whose protocol did not include doxorubicin ( median 162 days; range 31 to 1,575 days).  No difference was found in survival time between the two groups of cats (median 413 days for cats with doxorubicin; median 330 days for cats without doxorubicin).

Discussion / Conclusions: Cats presenting with macroscopic injection-site associated sarcomas have a significantly longer duration of remission when doxorubicin is included in the pre-operative radiation protocol.

To return to Sylvia's Cyber Kitty Condo just scratch her banner below...