Page 743 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 33 Hematopoietic Tumors 721

absent) intestinal thickening without mass effect similar if not Treatment and Prognosis
identical in presentation to LPE. The key elements necessary for In general, cats tolerate chemotherapy for lymphoma quite well,
the diagnosis of LGAL (and differentiation from IBD) include
VetBooks.ir procurement of tissue for histopathology, and if necessary, assess- most clients are happy with their choice to initiate treatment,
and quality of life generally improves after commencement of
ment of immunophenotype and clonality.
Abdominal ultrasound is by no means pathognomonic as therapy. 515,516
both LGAL and LPE can have normal ultrasound appearance
or reveal modest intestinal wall thickening with preservation of Low-Grade Alimentary Lymphoma
wall layering. 436,461,486,488,508–510 Changes, if present, predomi- LGAL is a gratifying disease to treat as durable remissions are gen-
nantly involves the muscularis propria and submucosal layers, erally achieved with well-tolerated, conservative treatment proto-
although mucosal thickening can also occur. Focal mural masses cols (e.g., oral chlorambucil and prednisolone). 486–488,504,517,518
are uncommon. Mesenteric lymphadenopathy is also common Chlorambucil (20 mg/m PO every 2 weeks [preferred by the
2
and reported in 45% to 80% of affected cats. LGAL generally author] or 2 mg PO every other day) and prednisolone (initially
involves the small intestine and, less commonly, the stomach and 1–2 mg/kg PO daily, reduced to 0.5–1.0 mg/kg every other day
large intestine. Cats with LGAL will uncommonly have ultraso- over several weeks) results in response rates (i.e., resolution of
nographic abnormalities in other abdominal organs such as the clinical signs) of greater than 80% and MSTs of approximately
stomach, liver, spleen, colon, and pancreas, and occasionally, mild 1.5 to 3.0 years. 486,488,491,504,517,518 Most clinical oncologists con-
effusions are observed. tinue these conservative protocols for 2 years or longer; however,
Cytologic evaluation of thickened bowel or associated mes- one report discontinued chlorambucil/prednisolone therapy at 1
enteric lymphadenopathy alone is generally not sufficient year. 517 Cats that relapse while receiving this protocol often will
for differentiating LGAL from LPE. 486,488,502 Therefore tis- subsequently respond to alternative alkylating agents, such as
2
sue procurement is required for diagnosis (and differentiation cyclophosphamide (200–250 mg/m , PO, q2–3 weeks) or lomus-
from LPE). The debate still exists as to whether endoscopically tine, or to reintroduction of chlorambucil if this had been discon-
obtained tissue is sufficient for diagnosis or if full-thickness tis- tinued. 505,517–519 Rescue protocols have reported MSTs ranging
sue procured during laparotomy or laparoscopy is necessary in from 9 to 29 months. Anecdotally, many will also respond to vin-
light of similarities with LPE. 436,487,491,509,511,512 Although his- blastine chemotherapy if they no longer are responsive to alkylat-
tologic morphology and intestinal infiltrative patterns (e.g., vil- ing agents. Ultimately, more aggressive CHOP- or MOPP-based
lous nests or plaques) can be highly suggestive of lymphoma, protocols may be utilized when more conservative protocols are
they may not provide a definitive diagnosis. Most agree that no longer effective.
although full thickness biopsies are preferred, less invasive endo- Prognostic factors for cats with LGAL are not well-defined
scopic biopsies, with ancillary immunophenotypic and molec- owing to the indolent nature of the disease and typical long-term
ular (i.e., PARR; see Chapter 8) assessments, are sufficient in survival. Only lack of response to initial induction chemotherapy
the majority of cases (see Table 33.10). If the differentiation of is consistently observed as a negative factor, although transmural
lymphoma and LPE is equivocal after standard histopathologic extension may also be associated with shorter STs. 487
assessment, the addition of immunophenotypic and clonality
analysis in a stepwise fashion, as proposed by several reports, Intermediate- or High-Grade Alimentary Lymphoma
enhances specificity and sensitivity and usually provides a defini- More aggressive multiagent combination chemotherapy is recom-
tive diagnosis. 436,441,479,480,487,489,491,513,514 As LGAL most com- mended for I/HGAL and LGL subtypes of lymphoma. The agents
monly involves the jejunum and ilium, endoscopic biopsy by used most commonly to treat intermediate- or high-grade lym-
both gastroduodenoscopy and ileocolonoscopy may be necessary phoma in cats are similar to those used for dogs with lymphoma
to procure representative samples. (see Section A in this chapter), and induction protocols currently
employed in cats are modifications of CHOP protocols initially
Intermediate- or High-Grade Alimentary Lymphoma designed for humans. 428,438–440,488,496,498,515,520–528 CHOP rep-
and Large Granular Lymphoma resents combinations of cyclophosphamide (C), doxorubicin (H,
The diagnosis of I/HGAL and LGL is generally less complicated hydroxydaunorubicin), vincristine (O, Oncovin) and prednisone
than for LGAL. 436,438,488,498 The former are often diagnosed with (P). In general, CHOP-based protocols are appropriate for cats
physical examination, abdominal imaging (e.g., ultrasound), with intermediate- and high-grade lymphoma involving any ana-
and cytologic or histologic assessment of needle aspirate or nee- tomic site (e.g., peripheral nodal, mediastinal, and extranodal
dle biopsy samples from intestinal masses, enlarged mesenteric forms), but should not be first-line therapy for low-grade variants
lymph nodes, or liver because mass lesions and gross lymphade- such as LGAL. As in the dog, a plethora of CHOP-based proto-
nopathy are more commonly present. Ultrasonographically, I/ cols have been reported for use in cats, although virtually no high-
HGAL is more likely to involve the stomach and colon than quality comparative data exist to compare outcomes. As such, the
LGAL. In a series of 16 cats with I/HGAL of the stomach, all protocol used should be based on cost, ease, client/veterinarian
had either ultrasonic evidence of wall thickening or the pres- preference, and level of comfort. One report found that cats may
ence of a mass, and 20% had abdominal lymphadenopathy. 439 better tolerate CHOP protocols that substitute vinblastine for vin-
Less commonly, abdominal exploration is necessary if lesions cristine; GI adverse events were less frequent and of lesser grade in
are subtle or not amenable to transabdominal sampling. Fur- cats receiving vinblastine. 529 The current CHOP-based protocol
ther staging via thoracic imaging, peripheral lymph node aspira- in use by the author for cats is presented in Table 33.11. This pro-
tion, and bone marrow assessment may be performed, but rarely tocol has been used in many cats with various forms of intermedi-
contributes prognostic information or alters treatment decisions ate- and high-grade lymphoma and is generally well tolerated. At
because the disease is already widespread and systemic therapy present, most canine lymphoma protocols involve a 12- to 25-week
is required. induction phase whereupon chemotherapy is discontinued and no