Page 1295 - Clinical Small Animal Internal Medicine

134 Lymphomas 1233

Immunophenotype preconceived notion of cancer and its treatment.
VetBooks.ir the population of lymphoid cells that make up the tumor. Therefore it should be made clear that the majority of
Immunophenotyping is commonly used to distinguish
dogs who receive chemotherapy will respond to treat­
Cell surface markers, such as CD3 and CD79a, aid in
of clinical signs related to lymphoma. In the author’s
differentiating T cell from B cell lymphomas. It is well ment and can achieve a remission in which they are free
established that dogs with a B cell form of lymphoma experience, most owners who decide to proceed with
have better response rates and prognosis compared to chemotherapy are cooperative, realistic, and apprecia­
those with a T cell phenotype. tive of the efforts made to help their pets.
Treatment options range from multiagent protocols to
Staging single‐agent prednisone and will be determined by the
Minimum database including a complete blood count location of the disease, the overall health of the pet, and
(CBC) with differential blood cell count, serum bio­ the emotional/financial commitment of the owner.
chemistry profile, and urinalysis should be completed to A primary veterinarian can easily manage many dogs
evaluate for the presence of paraneoplastic conditions with multicentric lymphoma. However, consultation
and rule out co‐morbid disease. with an oncologist may be helpful in establishing a treat­
Potential abnormalities related to lymphoma noted on ment protocol. Referral to an oncology center may be
a CBC include blood dyscrasias such as a nonregen­ indicated for atypical cases or for patients that are refrac­
erative anemia, thrombocytopenia, lymphocytosis or tory to treatment.
presence of circulating lymphoblasts. Bone marrow
aspiration is indicated in dogs with blood dyscrasias to Multiagent Chemotherapy Protocols
confirm lymphoma and rule out an unrelated blood Drugs with established activity include cyclophospha­
disorder. This may also help to differentiate between mide (C), doxorubicin (H, hydroxydaunorubicin or
multicentric stage V lymphoma and a primary lympho­ doxorubicin), vincristine (O, Oncovin®), and prednisone
blastic leukemia, which carries a worse prognosis. (P). Protocols incorporating these drugs are called
A chemistry profile that includes a serum ionized cal­ CHOP‐based protocols. All CHOP‐based multiagent
cium level is recommended to evaluate for the presence chemotherapy protocols are believed to be superior to
of hypercalcemia of malignancy and to assess liver and any single‐agent protocol with respect to remission
kidney function. duration and overall survival time. Multiple studies have
A urinalysis is helpful in evaluating renal function and demonstrated that approximately 80–90% of all dogs
can rule out a subclinical urinary tract infection. It is receiving a CHOP‐based chemotherapy protocol will
important to note that dogs with hypercalcemia of experience a clinical remission with an overall median
malignancy may present with azotemia and isosthenuria, survival time of 10–12 months. While success of treatment
which may not represent primary renal disease but is highly variable, the majority of multiagent protocols
instead is a consequence of the effects of hypercalcemia induce a first remission of >6 months after chemotherapy
on renal tubules. induction.
Thoracic and/or abdominal radiographs or abdominal Multiagent protocols are typically discontinued
ultrasound are recommended to determine the presence 15–19 weeks after the start of therapy. Long‐term main­
and extent of disease within visceral organs. When pre­ tenance chemotherapy has not demonstrated benefit
sent, pulmonary infiltrates typically appear radiographi­ with respect to remission duration or progression‐free
cally as diffuse interstitial and/or alveolar patterns. Rarely survival.
are there nodules or bronchial changes. Widening of the A commonly used and well‐studied chemothera py
cranial mediastinum may indicate the presence of medias­ protocol for dogs with newly diagnosed or naive
tinal lymphoma. multicentric lymphoma is the University of Wisconsin
Because of the potential for cardiotoxic effects of 19‐week discontinuous (short) CHOP protocol. This
certain chemotherapy drugs, thoracic radiographs are protocol is simple to administer since it relies on single‐
also important for assessment of cardiac changes. agent treatment at each visit, allowing for an assessment
of tolerability and efficacy of each drug. At week 19,
chemotherapy is discontinued if the dog is in complete
Therapy
remission (Table 134.2).
After establishing a diagnosis of lymphoma, a compre­
hensive discussion with the owner should encompass Single‐Agent Chemotherapy Protocols
goals, prognosis, associated costs, and potential compli­ As noted earlier, multiagent protocol drugs work best
cations. It is important to note that many owners have a when given in combination at the onset of therapy.