Page 1311 - Small Animal Internal Medicine, 6th Edition

CHAPTER 77 Complications of Cancer Chemotherapy 1283

bleomycin-containing protocols. Occasionally, dogs on
BOX 77.1 hydroxyurea develop generalized erythema.
VetBooks.ir Treatment of Local Tissue Reactions cohorts of dogs receiving Tanovea; this dermatopathy
Dermatologic toxicity has been identified in multiple
1. Apply an antibiotic ointment (with or without
corticosteroids) to the affected area and start systemic develops in up to 45% of dogs, and generally consists of
pruritic, focal otitis externa or focal erythemic skin lesions
antibiotics (amoxicillin/clavulanic acid). on the dorsum and in the inguinal region. This gener-
2. Bandage the area (and replace bandages daily). ally resolves with the institution of supportive treatments
3. Prevent self-mutilation by placing an Elizabethan collar (antibiotics for dermatitis, corticosteroids) and treatment
or a muzzle. interruption.
4. If there is no bacterial contamination (ruled out on the
basis of negative bacterial cultures), 10 to 20 mg of
methylprednisolone acetate (Depo-Medrol, Zoetis,
Madison, NJ) can be injected subcutaneously in the PANCREATITIS
affected area to alleviate pruritus and inflammation.
5. If severe necrosis or gangrene caused by anaerobic Pancreatitis is a well-recognized entity in human patients
contamination occurs, the area should be surgically undergoing chemotherapy. Offending drugs in humans
debrided. include corticosteroids, azathioprine, 6-mercaptopurine,
6. In the event of severe doxorubicin-induced soft tissue L-asparaginase, cytosine arabinoside, and combination che-
necrosis, the affected limb may need to be amputated. motherapy. Sporadic reports of pancreatitis in dogs (but not
in cats) receiving chemotherapeutic and immunosuppressive
agents have also appeared in the literature.
The author has documented acute pancreatitis in several
dogs receiving L-asparaginase or combination chemotherapy.
Dogs in the latter group were receiving COAP (cyclophos-
phamide, vincristine, cytosine arabinoside, prednisone);
ADIC (doxorubicin, DTIC); or VAC (vincristine, doxo-
rubicin, cyclophosphamide) chemotherapy. Clinical signs
developed 1 to 5 days after the start of chemotherapy and
consisted of anorexia, vomiting, and depression. Physical
examination findings in these dogs were unremarkable, and
abdominal pain was rare. The patients were treated with IV
fluids, and the clinical signs resolved within 3 to 10 days in
most dogs.
It is difficult to prevent chemotherapy-induced pancreati-
tis because it is not a predictable complication. As a further
precaution, dogs receiving drugs with the potential to cause
FIG 77.4 pancreatitis may be fed a low-fat diet.
Alopecia in a 7-year-old Schnauzer undergoing doxorubicin
and dacarbazine (ADIC) chemotherapy. Note the short and
light-colored haircoat.
CARDIOTOXICITY

Terriers (Fig. 77.4). It primarily affects the tactile hairs in Cardiotoxicity is a relatively uncommon complication of
short-haired dogs and cats. Although the exact reason that doxorubicin therapy in dogs; it is extremely rare in cats (one
chemotherapy-induced alopecia occurs in woolly-haired author has personally given cats more than 20 doses of doxo-
dogs is unknown, a prolonged anagen phase and syn- rubicin without signs of cardiotoxicity). Two types of
chronous hair growth, comparable with those occurring doxorubicin-induced cardiac toxicities are observed in dogs:
in human scalp hair, may make these dogs prone to this an acute reaction occurring during or shortly after adminis-
toxic effect. Drugs commonly associated with delayed hair tration and a chronic cumulative toxicity. Acute doxorubicin
growth and alopecia include cyclophosphamide, doxorubi- toxicity is characterized by cardiac arrhythmias (mainly
cin, 5-FU, 6-thioguanine, and hydroxyurea (Hydrea, E.R. sinus tachycardia) that develop during or shortly after
Squibb & Sons, Princeton, NJ). Alopecia and delayed hair administration. This phenomenon is thought to stem from
growth usually resolve shortly after discontinuation of the doxorubicin-induced histamine-mediated catecholamine
offending agent. release because the sinus tachycardia and hypotension can
Hyperpigmentation is uncommon in dogs and extremely be prevented by pretreatment with H 1 and H 2 antihistamines.
rare in cats receiving chemotherapy. Cutaneous hyper- Several weeks or months after repeated doxorubicin injec-
pigmentation affecting the face, ventral abdomen, and tions, persistent arrhythmias, including ventricular prema-
flanks is common in dogs receiving doxorubicin- and ture contractions, atrial premature contractions, paroxysmal