March 10, 2018

Treatment Options for Feline Splenic Mast Cell Tumors

Splenectomy significantly increases median survival time, although the benefit of chemotherapy and supportive care remains unknown.
By Natalie Stilwell, DVM, MS, PhD
Splenic mast cell tumor (MCT) is a common neoplasia in geriatric cats with no apparent breed or sex predilection. Generally classified into 1 of 3 categories—cutaneous, splenic, or intestinal—MCT commonly causes anemia and mastocytemia, an increase in circulating mast cells. Splenectomy is currently considered the treatment of choice for these cases, yet it is unknown whether additional therapies, including adjuvant chemotherapy and steroids, further increase survival time.

Recently, a group of researchers from several veterinary hospitals in the United States conducted a retrospective study of 64 cases to evaluate the role of chemotherapy and supportive care on splenic MCT outcomes in cats.

Methodology
Veterinary records were examined from client-owned cats presenting to 3 veterinary teaching hospitals in the U.S. Most cats presented with non-specific gastrointestinal signs, and splenic MCT diagnosis was confirmed via cytology or histopathology after splenectomy. Cases included those with concurrent cutaneous MCT and/or visceral involvement. Chemotherapy included steroid treatment, while histamine blockers and proton pump inhibitors were designated as supportive care. Cases were categorized according to treatment group:
  1. splenectomy
  2. splenectomy with adjuvant chemotherapy
  3. chemotherapy alone
  4. supportive care

Of the 64 cats that met the inclusion criteria for the study, the median age was 13 years and there was an equal distribution of males and females. Within the group:
  • 20 cats were treated for MCT via splenectomy alone
  • 20 cats received a splenectomy with adjuvant chemotherapy
  • 15 cats received chemotherapy alone
  • 9 cats received only supportive care

The most commonly recorded clinical signs were weight loss (56%), anorexia (48%), vomiting (45%), and lethargy (42%). Splenomegaly was noted in 44% of cats upon physical examination and 30% had concurrent cutaneous MCT. Anemia and mastocytemia were noted in 47% and 35% of evaluated blood samples, respectively, and metastasis to the liver was present in 52% of biopsy or fine needle aspirate samples. Abdominal lymph node involvement was noted in 40% of the cases evaluated via abdominal ultrasound or laparotomy.

RELATED:
Median survival time was significantly longer for cats that had a splenectomy than for cats that did not (856 vs. 342 days), however, the addition of adjuvant chemotherapy after splenectomy did not further increase survival rates. Seventy percent of cats in the study died from tumor-related causes.

Concurrent cutaneous MCT regressed in 4 of 19 cats, including 3 after splenectomy alone and 1 after adjuvant chemotherapy. Complete regression of mastocytemia, which was noted in 10 of 22 cats, occurred a median of 58 days after treatment. Although the study’s sample size was small, anemia, mastocytemia, and metastasis to the liver or lymph nodes were not negative prognostic factors.

In conclusion, the authors found that splenectomy significantly improved survival time for cats with splenic MCT, making it the treatment of choice for this diagnosis. The role of chemotherapy and supportive care in the outcome of feline splenic MCT remained unclear.

 
Dr. Stilwell received her DVM from Auburn University, followed by a MS in Fisheries and Aquatic Sciences and a PhD in Veterinary Medical Sciences from the University of Florida. She provides freelance medical writing and aquatic veterinary consulting services through her business, Seastar Communications and Consulting.

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