Surgical Excision of Soft Tissue Fibrosarcomas in Cats

Ellen B. Davis, DVM, Clare R. Gregory, DVM, Phillip H. Kass, DVM, PhD

Short and Sweet. The study reviews and analyzes the medical records of 35 cats with soft tissue fibrosarcomas that had been treated by either 1) single surgical excision 2) multiple surgical excisions, or 3) one or more surgical excisions plus radiation therapy. The authors conclude that complete surgical excision of fibrosarcomas in cats is possible and can be curative. Complete surgical excision in the cases reviewed resulted in significantly higher tumor free intervals and survival times than incomplete excision and / or radiation therapy. Radiation therapy was used in cases with incomplete surgical excision or cats with tumor recurrence. It did not appear to increase the tumor free interval or survival time in these cats.

Study and design Population. Retrospective study. The medical records of 45 cats with histologic diagnosis of soft tissue fibrosarcoma (FSA) that presented to the VMTH from July 1994 - November 1995 were reviewed.

Of these 45 cases, 10 were excluded from the study analysis because they were lost to follow-up (2/10) or they were euthanized or received no treatment following diagnosis (8/10- all died within 1 month of diagnosis).

The remaining 35 cats were divided into 3 groups based on the treatment they received: Group 1- a single surgical excision or amputation (11/35) ; Group 2- more than one surgery (7/35) ; or Group 3- more than one surgery followed by adjunct radiation therapy (17/35).

The cats ranged in age from 4-15 years old ( mean 8.9 years, median 8 yr). There were 18 castrated males and 1 spayed females. Breeds included DSH (20/35), DLH (11/35), Manx (2/35), Himalayan cross (1/35) and a Siamese (1/35).

Of the 35 cats, 26 were currently vaccinated ( 22 for both rabies and FeLV, 3 rabies only, 1 FeLV only) and 9 either had not been vaccinated (3/9) or the vaccination status was unknown (6/9).

RESULTS

Overall the 35 cats had a median tumor-free interval of 10 months and median survival time of 11.5 months (range=1-40 months) at the time of follow-up. Thirteen (37%) were tumor free for more than a year (10 for > 12 months, 3 for > 24 months). Thirteen cats (group 1=7, group 2=4, group 3=2) were still alive and tumor free at the time follow-up was completed, ranging from 2-40 months since the final treatment. Two other cats died of unrelated causes and were tumor free at the time of death. Of the remaining 20 cats, 9 had metastasis, 9 had extensive local tumor recurrence, 1 was euthanized due to radiation damage, and 1 died from progressive illness of unknown cause.

Complete vs Incomplete Excision. Complete surgical excision, based on histologic exam of tissue margins, was achieved in 16/35 cats. The median tumor free interval and survival times in these cats with complete surgical excision were both > 16 months (mean=13.4 months for each). Of the 13 cats that survived more than a year, 9 (69%) had complete surgical excision or amputation with no radiation therapy. In comparison, the median tumor free interval in cats with incomplete surgical excision was 4 months (mean=8.1) and the median survival time was 9 months (mean=10). Both the tumor free interval and survival time were significantly greater in cats with complete surgical excision vs cats with incomplete surgical excisions. At the time of follow-up 11/16 cats with complete excision showed no evidence of tumor recurrence vs only 4/19 cats with incomplete excision.

Comparison By Treatment Group showed that the median tumor-free interval and the median survival time were both over 16 months in group 1 cats compared with a median tumor free interval of 5 months and a median survival time of 13 months in group 2 cats, and a median tumor free interval of 4.5 months and median survival of 9 months in group 3 cats.

FeLV Status. The FeLV status was know in 32/35 cats. Only 3 were seropositive on ELISA for FeLV antigen. One of these cats developed lymphosarcoma. Median tumor-free interval and median survival time were each 8 months in these 3 cats. One other cat with a FSA on the pinna showed the presence of FeLV antigen on the excised tumor tissue even though the cat was seronegative for FeLV. This cat was alive and tumor free 29 months postop.

Tumor Classification based on histological grade was available in 29/35 cases. Low grade tumors (<5 mitotic figures/hpf, or hpf) were seen in 14 cases; moderate grade (5-10 mitotic figures/hpf or pleomorphism) in 9 and high grade (>10 mf/hpf, or the tumor had marked pleomorphism or was poorly differentiated) in 6.

In the 14 cats with low grade tumors the median tumor free interval was 15 months (mean=13.8) and the median survival was 15.5 months (mean=14.6). In the 9 cats with low grade tumors the median tumor free interval was 4 months (mean=10.2) and the medium survival was 8.5 months (mean=11.5). In the 6 cats with high grade tumors the median tumor free interval was 6.5 months (mean=8.3) and the median survival was 10 months (mean=8.5). Of the 13 cats that survived more than a year 8 had low grade tumors, 3 moderate, and 2 high grade tumors.

Amorphic or granular refractile material, or perivascular lymphocytic-plasmacytic infiltrates were reported in the tumors in 4 cats.

Tumor Location included the trunk (28/35 - 24 interscapular or dorsal cervical / thoracic, 3 flank, 1 pinna) or appendicular (7/35 - 4 caudal thigh, 3 antebrachium or the elbow).

In the cats with appendicular tumors, amputation was done in 4/7 and wide local excision in 3/7. Amputation resulted in complete excision in 3/4 cases. Wide local excision resulted in incomplete excision in all 3 cases.

No significant differences in either tumor free interval or survival time were found between tumors located on the trunk vs appendicular location. In the cats with tumors located on the trunk the median tumor free interval was 9 months (mean=9.1) and median survival time was 11 months (mean=10.4). In the cats with appendicular tumors the median tumor free interval was 15 months (mean=16.3) and median survival time was 15 months ( mean=16.4).

Radiation Therapy (group 3) was done in 17 cats following surgical excision using 60 teletherapy, iridium 192 brachytherapy, or both, and +/- carboplatin. It should be noted that 15/17 of cats undergoing radiation therapy either had incomplete surgical surgical excisions or tumor recurrence and the remaining 2 cats were suspected of having tumor recurrence. The median tumor free interval of 4.5 months and median survival of 9 months were significantly lower than in groups 1 and 2.

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