58° Congresso Nazionale SCIVAC: Oncologia veterinaria

58° Congresso Nazionale SCIVAC • Milano, 7-9 Marzo 2008 • Oncologia veterinaria - Alle soglie del III Millennio
nase-2 signaling as a direct growth stimulant to urothelial cells. In one study
of 34 dogs treated with piroxicam, there were 2 complete remissions, 4 partial
remissions, 18 with stable disease, and 10 with progressive disease. The
median survival time was 181 days, however, the quality of life was improved
in all of the dogs. Other non-steroidal COX-2 inhibitors may also be useful
in transitional cell carcinoma. A recent report of firocoxib at a dose of 5
mg/kg PO daily combined with 60 mg/m 2 IV cisplatin every three weeks
showing promise in the dog, with a 50% response rate noted for 12 dogs receiving
this therapy.
A multicenter trial sponsored by the Veterinary Cooperative Oncology
Group revealed that 48% of 55 dogs enrolled had measurable responses to a
combination of mitoxantrone and piroxicam. Mitoxantrone was administered
at 5 mg/m 2 every 21 days for 4 cycles, and piroxicam was administered at 0.3
mg/kg/day throughout the trial period. Of 48 evaluable dogs at the end of
study, only one dog had a complete response, while 16 had partial responses
and 22 had disease stabilization. Gastrointestinal toxicity and azotemia were
the most common adverse effects, seen in 18% and 10% of treated dogs, respectively.
Median time to treatment failure was 194 days, and median survival
time was 350 days, demonstrating the indolent nature of TCC even in the
case of incomplete response.
Intravesicular therapy with such agents as cisplatin, methotrexate, cyclophosphamide,
and 5-fluorouracil have been effective in humans. This form of
therapy is most effective against superficial tumors that are not invasive into
the bladder wall. Some evidence suggests that intravesicular therapy may irradicate
residual disease after incomplete resection. Unfortunately, most bladder
tumors in dogs are invasive at the time of diagnosis. Intralesional BCG at
the time of partial cystectomy showed variable results. Two of seven dogs
treated intraoperatively with BCG showed clinical benefit, but two dogs developed
severe granulomatous reactions with secondary obstruction. Recently,
intravesicular therapy with mitomycin C has been attempted in dogs
with evident safety, but studies are preliminary.
Radiation Therapy - There are few reports on the effectiveness of radiation
therapy use in the control of bladder tumors. In one study, intraoperative radiation
therapy followed by fractionated external beam irradiation resulted in
poor local control and serious bladder fibrosis with resultant incontinence.
Fractionated external beam irradiation alone requires using traditional fractionation
of 3-4 gy/radiation fraction has been attempted with poor long term
results due to the cumulative doses of radiation needed for eradication of the
cancer. Significant risk of serious bowel injury can be reduced by utilizing
small dose-per-fraction therapy over an extended time period (2.7 Gy x 20
fractions). Combination of radiation with mitoxantrone and prioxicam has
been reported to improve clinical signs in 7/10 dogs so treated.
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