Addressing gastrointestinal lymphomas in felines

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Results from a 2022 study found 78% of 860 submitted feline intestinal biopsy specimens confirmed evidence of lymphosarcoma (LSA), with most cases of the disease occurring in the small intestine and stomach.¹ Using these data, Steven Suter, VMD, PhD, MS, DACVIM (Oncology), explained the prevalence of LSA in cats during a lecture at the North American Veterinary Community’s 2023 Veterinary Meeting & Expo in Orlando, Florida, adding that he has seen an overall increase in feline lymphoma worldwide. He also concluded that the growing prevalence may be credited to the increase in number and frequency of alimentary and extranodal forms of lymphoma, especially gastrointestinal (GI).²

With this increasing number of cases, Suter shared some proposed etiology for feline GI lymphoma, including but not limited to the following:

• A link may exist between chronic cigarette smoke exposure (5 years or more) and lymphoma, but location of the disease related to this exposure is not specified.³
• Chronic inflammation from chronic irritable bowel disease has been linked to the development of alimentary LSA.²
• Siamese cats may have a predisposition (most likely genetic) to developing mediastinal LSA.²
• Feline immunodeficiency virus infection and subsequent immunosuppression has been implicated in feline lymphomagenesis.²

Diagnosis

“The big point of this talk is that GI lymphomas in cats are not created equal, but they do have similar clinical signs. The signs, when cats are presented at their local veterinarian, tend to be similar, [including] weight loss, chronic vomiting, diarrhea, and inappetence. [These] are the hallmark signs of a cat who has GI lymphoma,” Suter said.

“In physical exam, many times you feel nothing, and other times you can feel thickened, rope-like intestines. Many times, [the patient will] have an actual abdominal mass which is usually associated with a small intestine. You can palpate enlarged, especially mesentery lymph nodes, but not all the time,” he continued.

Suter reminded attendees that although they have similar clinical signs, GI lymphomas can have very different treatments. “Figuring out [the] type of GI lymphoma is important because that will guide our treatment options when treating these cats,” Suter said.

Ultrasound-guided fine-needle aspiration (FNA) can be effective for diagnosing this disease. However, Suter stated this method can be challenging if the GI thickening/mass or regional lymph nodes are not large enough to obtain cells from. “As with any tumor, biopsy is always a gold standard…and it’s very easy to [perform] biopsy [for] cats.” As a result, Suter recommended a biopsy for everything in the GI tract during abdominal surgery because GI lymphoma can occur in all portions of the GI tract.

Suter also recommended that complete diagnostics should include abdominal ultrasound, transabdominal ultrasound-guided FNAs or needle biopsy of affected organs, thoracic radiographs (which may or may not contribute any prognostic information but may identify other comorbidities), complete blood count, and serum chemistries. Staging in oncology measures the extent of the tumor burden. This can help determine whether local, systemic, or combined treatment is warranted for the patient, usually dependent on where the disease presents.²

Treatment

Low-grade GI LSA is typically easier to manage, according to Suter. “Most cats generally respond quite well,” he added.

Suter recommended using chlorambucil (Leukeran) and prednisolone chronic dosage scheme, which is currently the standard of care for this disease. This treatment has an 80% response rate for cats, with a median survival rate of 1 to 3 years.²

Intermediate- to high-grade GI LSA requires a completely different protocol for treatment. “As we always say in oncology, aggressive diseases require aggressive treatments,” Suter said.

Standard of care for managing this type of GI LSA is CHOP-based chemotherapy, which includes 4 drugs: cyclophosphamide (Cytoxan), doxorubicin (Adriamycin), vincristine (Oncovin), and prednisolone. This treatment is administered weekly, but it can be difficult for some clients to transport their cat to the hospital each time, Suter noted. Surgery before starting chemotherapy can be considered if a large GI mass is seen or clinical signs related to constipation/obstipation are seen. Response rate for this treatment is approximately 50% to 60%, with a median survival rate of 6 to 12 months.²

With these median survival rates, Suter reminded veterinary professionals to be careful when telling clients how long their pet is likely to live. “I’ve seen cats live 2 years, [and] I’ve seen cats live 1 month. It’s difficult to define exactly how an animal is going to [respond to treatment]…but usually more aggressive treatments cause longer survivals,” he said.

References

1. Kehl A, Törner K, Jordan A, et al. Pathological findings in gastrointestinal neoplasms and polyps in 860 cats and a pilot study on miRNA analyses. Vet Sci. 2022;9(9):477. doi:10.3390/vetsci9090477
2. Suter S. Feline gastrointestinal lymphomas: diagnosis and treatment. Presented at: Veterinary Meeting & Expo; January 14-18, 2023; Orlando, FL.
3. Bertone ER, Snyder LA, Moore AS. Environmental tobacco smoke and risk of malignant lymphoma in pet cats. Am J Epidemiol. 2002;156(3):268-273. doi:10.1093/aje/kwf044