Page 1329 - Small Animal Internal Medicine, 6th Edition

CHAPTER 79 Lymphoma 1301

patient is used in an attempt to determine the extent of gists. This can be done by immunocytochemistry, immu-
disease and correlate it with the prognosis. Unfortunately, it nohistochemistry, FCM, or PARR. But the main question
VetBooks.ir has little prognostic value (i.e., animals with stage I disease is: Should every dog or cat with lymphoma be immuno-
phenotyped before initiating therapy? The blanket answer
have survival times similar to those of animals with stage IV
disease). The only prognostic information of clinical rele-
mainly in dogs with multicentric lymphoma; however, in our
vance in this system is the fact that asymptomatic (i.e., sub- is “no.” Phenotype has been shown to change the prognosis,
stage a) dogs with lymphoma have a better prognosis than experience, it rarely changes the initial treatment approach.
“sick” (i.e., substage b) dogs. As discussed earlier, with the In dogs, a T-cell phenotype is quite likely if the patient is
novel FCM analyzer’s use for in-house CBCs, circulating a Boxer, has hypercalcemia or a mediastinal mass, or has
neoplastic cells are frequently identified in the graphics; cutaneous involvement.
therefore these patients who would have previously been Although multiple previously published reports suggest
classified as stage III, now undergo “stage migration” to stage that dogs with large-cell T-cell lymphoma treated with stan-
V disease. dard combination chemotherapy have a worse prognosis for
A staging system that takes into account tumor bulk and remission and survival than dogs with B-cell tumors; in one
FeLV status in cats with lymphoma provides some prognos- of the author’s experience (GC), this is not the case. In a
tic information. Until a new system is devised, it is advisable previous study, T-cell phenotype was not a negative prognos-
to determine the prognosis on the basis of the patient’s tic factor in dogs with lymphoma treated with COP- or
overall clinical condition, the FeLV status (in cats), and any CHOP-based protocols (Hosoya et al., 2007). This is likely
constitutional signs or severe hematologic and biochemical because most dogs with T-cell lymphoma received lomustine
abnormalities the patient may have. Another important issue (CCNU), a drug that may be more effective in patients with
is that, even though a specific staging protocol may be of T-cell phenotype.
some prognostic value in patients treated with a given che-
motherapy protocol, it may not be so when a different drug Treatment
combination is used. Moreover, at this time the effectiveness Once a diagnosis of lymphoma is established, the prognosis
of more aggressive protocols in dogs and cats with advanced- and potential therapeutic options should be discussed with
stage lymphoma is unknown. the pet’s family. Remission rates in cats and dogs with lym-
At least a CBC, a serum biochemistry profile, and a uri- phoma treated with various chemotherapy protocols are
nalysis should be performed in all cats and dogs with lym- approximately 65% to 75% and 80% to 90%, respectively.
phoma whose owners are contemplating therapy. In addition, Most cats with multicentric or mediastinal lymphoma treated
FeLV and FIV tests should be performed in cats. The result- with multiple-agent chemotherapy protocols are expected to
ing minimum database can provide a wealth of information live 6 to 9 months; approximately 20% to 30% of the cats live
that can help the owner (and clinician) decide whether the more than 1 year. Cats with small cell intestinal lymphoma
patient should be treated. In addition, once a decision to typically live in excess of 2 years, with response rates of
treat the pet has been made, the nature of any clinicopatho- >90%. Most dogs with lymphoma treated with multiagent
logic abnormalities usually dictates the treatment or treat- chemotherapy are expected to live 8 to 16 months; approxi-
ments used. For example, in a dog with pronounced mately 20% to 30% of the dogs are alive 2 years after diag-
cytopenias caused by lymphomatous infiltration of the bone nosis. The approximate survival time in untreated cats and
marrow, a highly myelosuppressive chemotherapy combina- dogs with lymphoma is 4 to 8 weeks. The reasons for the
tion will almost certainly result in severe neutropenia and shorter survival times in cats as compared with dogs with
sepsis; it should therefore be avoided. L-asparaginase is a lymphoma is that their initial response rates (especially, the
useful initial treatment in this situation, as it does not have complete response rates) are lower, and along with this,
myelosuppressive effects. remissions appear to be difficult to reinduce once their
In cats and dogs with suspected CNS lymphoma, it is disease has relapsed. In addition, the retrovirus-associated
advisable to perform cerebrospinal fluid (CSF) analysis and nonlymphomatous disorders that affect cats with lymphoma
advanced imaging (i.e., computed tomography [CT] scan or lead to shortened survival times (i.e., FeLV infection is a
magnetic resonance imaging [MRI]). The finding of high negative prognostic factor in cats with lymphoma).
numbers of neoplastic lymphoid cells and an increased In our experience, even if a patient has stage I nodal or
protein concentration in a CSF sample is diagnostic for lym- extranodal lymphoma at the time of presentation, systemic
phoma. Because of their poor accessibility, the diagnosis of dissemination of the disease usually occurs within weeks
extradural masses usually requires the collection of a surgical to months of diagnosis. However, occasionally solitary oral
specimen for cytologic or histopathologic evaluation. As dis- or cutaneous lymphomas may behave as true stage I dis-
cussed earlier, the authors’ clinics assume that any dog or cat eases (i.e., there is no systemic dissemination). Therefore
with lymphoma and central neurologic signs has CNS the mainstay of treatment for patients with lymphoma is
involvement until proven otherwise, and it is treated appro- chemotherapy, given the fact that lymphomas are (or will
priately (see later). become) systemic neoplasms. Surgery, radiotherapy, or both
As previously discussed, immunophenotyping of canine can be used to treat localized lymphomas before or during
and feline lymphoma has become routine for most oncolo- chemotherapy. Half-body irradiation and bone marrow