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An Urban Experience
For high grade large cell (EATL type I), the diagnosis is typically more straightforward with GI masses, enlarged mesenteric LN, or liver involvement. The diagnosis is typically made with abdominal ultrasound and cytology/ histology. Surgery is less commonly needed.
For low grade small cell (EATL type II), intestinal thickening is often modest or absent and similar to IBD.
Cytology alone is often insufficient and will come back
as benign hyperplasia. To confirm the diagnosis, AUS and histopathology are typically needed, and may require phenotype and clonality.
It can be challenging to distinguish low grade vs IBD
with abdominal ultrasound. With low grade GI LSA, 60-90% have an abnormal AUS with 50-70% diffuse
SI thickening, predominantly muscularis propria and submucosa layers. Mesenteric lymph nodes are abnormal in 45-80%. Focal GI masses are uncommon. For IBD, 10-50% have diffuse SI thickening and mucosal thickening more common. The incidence of mesenteric LN lymph nodes is lower at 15-20%, and other abnormal organs are typically normal.
Cytology is rarely useful for distinguishing low grade GI LSA vs IBD. The debate rages on regarding endoscopy vs full thickness biopsy (laparotomy vs laparoscopy).
On histopathology, lymphoma typically has lymphoid infiltration beyond mucosal layer, epitheliotrophism, heterogeneity, and lymphocyte nuclear size consistent with malignanct. If diagnosis is still equivocal, phenotype or PARR is recommended.
There are less feline data than for canine lymphoma. Papers often lump together small number of cases
of multiple subtypes of various anatomic, phenotype and histologic grades. Outcomes are less predictable in cate and there is greater variation in histologic
type and anatomic location in cats. But cats tolerate chemotherapy well and better than dogs. Febrile neutropenia is rare. Most owners happy they chose to treat and QOL improves.
Which protocol? For intermediate and high grade/ EATL I, there is an overall response of 50-80%, a median remission of 4 months, and a median survival 6 months. Cats that achieve a complete remission have
a MST of 1 year. I typically recommend a CHOP multi- agent protocol such as the UW 25 week protocol. When using doxorubicin in cats, I use a lower dose (1 mg/kg). Cardiac toxicity is not clinical problem in cats in contrast to dogs, and renal function (BUN, Cr, USG) should be monitored in cats when giving doxorubicin. In dogs, data supports shorter maintenance-free protocol, but there
is no data in cats, and some cats may need chronic chemotherapy.
An alternative protocol is the COP protocol with reported complete remissions of 50-70%. This is commonly
used in used in Europe with similar results to CHOP in
1 study. While the protocol requires less frequent visits,
it is a longer 1 year protocol. Other studies support the addition of doxorubicin to COP for durable responses.
For single agent options, Lomustine can be given at 50-60 mg/m2 every 4-6 weeks, which is given at a lower dose and less frequently than dogs. Single agent doxorubicin is cats is less successful with complete remission rates of <50%.
For low Grade/ EATL type II, less aggressive chemotherapy protocols are typically used. Oral chlorambucil (Leukeran®) can be dose with pulse dosing (20mg/m2 every 2 weeks or 15 mg/m2 for 4 days every 3 weeks) or with chronic dose (>4 kg start @ 2 mg PO q 2 day, maintenance q 3 days; <4 kg start @2 mg PO q 3 day, maintenance q 4 days). For cats I prefer prednisolone, typically at 1 - 2 mg/kg orally daily and reduce to 0.5 to 1 mg/kg daily. In some cases, prednisolone may be discontinued.
For relapsed cases, cyclophosphamide, Lomustine, and vinblastine are recommended. For severe or refractory cases, I will used CHOP or COP protocols
Nutrition for EATL type II: With evidence of role of inflammation and many have concurrent IBD, there is thought to consider transition to a novel protein diet and add probiotics. I also recommend running B12 levels, and supplementing as indicated.
Prognostic factors: The prognosis and response
in cats is more variable than in canine lymphoma. Prognostic factors include anatomic location, achieving a CR, FeLV status, substage, and a multi-agent protocol (CHOP vs COP?). Factors that are NOT prognostic in cats include stage and immunophenotype, age, weight, gender, and FIV
For GI forms, the prognosis is overall extremely variable. For EATL type I, response rates are 50-75%, median remission duration is 4-6 months, and expected survival is 6-8 months. 15-25% can live 1-2 years. For EATL type II, remission is generally defined as improvement or resolution of clinical signs, 70%-85% will respond for a median survival time of >2 years.
1. Vail DM. Feline Lymphoma and Leukemia. In: Small Animal Clinical Oncology. 5th ed. St. Louis Missouri: Elsevier Saunders; 2013:638-653.
2. Williams LE. Lymphoma, Cat (Multicentric). In Clinical Veterinary Advisor Dogs and Cats. 3rd edition. St. Louis Missouri: Elsevier Mosby; 2015: 610-613.
3. Bryan JN. Lymphoma.In Cancer Management in Small Animal Practice. Saunders 2010. 290-295
4. Norsworthy GD, et al. JAVMA 2013, 243 (10): 1455-1461.

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