Page 1332 - Small Animal Internal Medicine, 6th Edition

1304 PART XII Oncology

again on a modified maintenance protocol. If at the end of (e.g., Poodle, Bichon Frise); cats (and some dogs) may also
the induction phase the patient is not in a CR, the author shed their tactile hairs during treatment.
VetBooks.ir recommends that intensification with L-asparaginase be done pet’s appetite and activity level, measure their lymph nodes
During this phase, owners are instructed to monitor their
before the maintenance phase is initiated. In addition to the
chemotherapeutic approach discussed in this section, a
take their pet’s rectal temperature if they are unwell (pyrexia
variety of protocols have been used successfully in the treat- (if peripheral lymphadenopathy was present initially), and
ment of cats and dogs with lymphoma. (See Suggested Read- is usually secondary to neutropenia and bacteremia or
ings for additional information.) sepsis). If pyrexia develops, owners are instructed to contact
Induction of remission their veterinarian immediately so that their pet can undergo
As previously discussed, one author’s (GC) protocol of a complete physical examination and CBC (for additional
choice for the induction of remission is COP. The agents in information, see Chapter 77). Treatment with COP results in
this protocol consist of cyclophosphamide, vincristine, and CR within 1 to 14 days of the start of therapy in most animals
prednisone; these drugs are currently available as generic (>85% in dogs, >70% in cats) (Figs. 79.9 and 79.10, A and
products and are relatively inexpensive. The dosages are B). This remission is usually maintained throughout the
specified in Box 79.1. These drugs belong to three different induction phase.
categories, have different mechanisms of action, and do not In dogs with diffuse large-cell alimentary lymphoma, the
have superimposed toxicities. In dogs or cats with CNS or authors both use a CHOP-based protocol (see Box 79.1)
ocular involvement, cytosine arabinoside can be added by because, on the basis of experience, the response rate to
the subcutaneous (SC) route or as a continuous rate infusion COP is low. This protocol is more expensive and slightly
for 6 to 8 hours (COAP protocol); given its short half-life more likely to cause adverse effects than the COP protocol.
and S-phase–specific mechanism of action, an IV bolus
injection results in minimal cell kill. SC administration of
this drug is painful in cats (and in some dogs). The induction
phase lasts 6 to 8 weeks, and weekly chemotherapy visits are
necessary during this time.
During the induction phase, toxicity is minimal (<15%)
and client compliance is high because most of the toxic signs
are hematologic (i.e., cytopenias) and usually do not result
in clinical signs that can be detected by the owners. The
dose-limiting toxicity of this induction protocol is hemato-
logic (i.e., myelosuppression leading to neutropenia), and it
occurs in less than 10% of the patients; the neutrophil nadir
usually occurs around day 7 or 8 because two myelosuppres-
sive agents (i.e., cyclophosphamide and cytosine arabino-
side) are given during the initial 2 to 4 days of treatment in
the COAP protocol. In most cases, the neutropenia is mild A
(2000-3500 cells/µL). The neutropenia can be severe if the
animals have neoplastic bone marrow infiltration before the
initiation of treatment, have FeLV- or FIV-associated myelo-
dysplasia or other retrovirus-associated bone marrow disor-
ders, or receive the cytosine arabinoside by constant-rate IV
infusion rather than by the SC route. Also, anecdotally, neu-
tropenia appears to be common in Cocker Spaniels and West
Highland White Terriers receiving this protocol. Dosage
adjustments in cats and dogs that develop neutropenia are
described in Chapter 77. Gastrointestinal toxicity is minimal
to nonexistent; however, cats receiving cyclophosphamide
can occasionally become anorectic. Consequently, this drug
should be administered once every 3 weeks in cats (as
opposed to every other day as in dogs; see Box 79.1). If
anorexia develops, treatment with cyproheptadine, an anti- B
serotonin drug, at a dosage of 1 to 2 mg per cat PO every
12 h or mirtazapine at a dosage of 1.875 to 3.75 mg per cat FIG 79.10
PO every 1 to 3 days is indicated. Capromorelin, is a novel Mixed-breed dog with multicentric lymphoma before (A)
appetite stimulant (Entyce, Aratana Therapeutics, Leawood, and 7 days after initiating chemotherapy (B). Note
KS) given at a dosage of 3 mg/kg PO every 24 h. Hair loss is complete disappearance of mandibular lymphadenopathy
also minimal, and it occurs primarily in woolly-haired dogs and ventral facial edema.