On Day 27 after surgery, the cat began receiving adjuvant chemotherapy at the University of Minnesota. Mitoxantrone (1.75
mg [6 mg/m2 ] intravenously) was administered on Days 27, 48, 69, and 90 after surgery. A CBC performed about seven days after each mitoxantrone
treatment revealed leukopenia after the first two treatments (Table 1); each time the cat was given prophylactic oral amoxicillin trihydrate-clavulanate potassium (62.5 mg orally twice daily
for seven days) and metoclopramide (2.5 mg orally three times daily, as needed) and did not develop clinical signs associated
with the low white blood cell counts. The cat tolerated the mitoxantrone well with no reported adverse effects, although it
lost 1 lb (0.45 kg) between the second and third treatments. The client did not mention any change in the cat's appetite.
Possible causes for the weight loss would be decreased appetite (e.g. secondary to the medications) or cancer cachexia.
5. Ventrodorsal (left) and right lateral (right) thoracic radiographs taken on Day 90 after surgery. A diffuse bronchial pattern
is present, and a large soft tissue density mass in the cranial mediastinum (arrow) is most apparent in the lateral view.
Surgical clips from the previous nephrectomy are noted within the abdomen just cranial to the remaining kidney (arrowhead),
which appears radiographically normal.
On Day 83 after surgery, the cat was presented to the University of Minnesota for evaluation of ocular problems. Horner's
syndrome was noted in the left eye, but the cat's vision was apparently unaffected, and the globe and fundus examination results
were normal. There were no other neurologic deficits. On physical examination, the cat was thin and had lost another 1.5 lb
(0.68 kg) since its last visit (on Day 69 after surgery), for a total loss of 2.5 lb (1.14 kg), or 22.8% of body weight, since
the second mitoxantrone treatment on Day 48 after surgery. The differential diagnoses for the Horner's syndrome were metastatic
neoplasia affecting the vagosympathetic trunk, spinal cord, or brainstem or an idiopathic cause (due to the lack of other
concurrent neurologic clinical signs).
On Day 90 after surgery, the cat received a fourth dose of mitoxantrone. The Horner's syndrome persisted, and a topical 10%
phenylephrine test revealed a partial response, with some resolution of the miosis in the left eye at 10 minutes and then
no further change out to 60 minutes. Physical examination findings were unchanged from the previous visit. The results of
a CBC were within reference ranges (Table 1), and the results of feline immunodeficiency virus antibody and feline leukemia virus antigen tests were negative.
Three-view thoracic radiographs revealed a left-sided soft tissue mass in the cranial mediastinum near the thoracic inlet
(Figure 5). The most likely differential diagnosis for this mass was metastatic spread of the primary renal transitional cell carcinoma.
The mediastinal mass was thought to be the most likely cause of the cat's Horner's syndrome. Additionally, there was a moderate,
diffuse bronchial pattern not seen on the previous radiographs. The bronchial pattern was consistent with moderate to severe
bronchial disease, although an atypical presentation for metastasis could not be ruled out.