58° Congresso Nazionale SCIVAC: Oncologia veterinaria

58° Congresso Nazionale SCIVAC • Milano, 7-9 Marzo 2008 • Oncologia veterinaria - Alle soglie del III Millennio
TREATMENT
Surgical resection, if possible, is the treatment of choice and can be curative
for small tumors located distant to the trigone. Unfortunately, most TCC
are located in the trigone and may extend into the urethra, prostate, and ureters.
If the cancer is located in the apex of the bladder, a very wide full-thickness
partial cystectomy may be attempted. More than 80% of the bladder can
be removed with eventual return to normal function and capacity. Even if surgical
resection is possible, most patients will have local recurrence or metastsis
within one year. Translocation of the ureters to the colon by performing a
complete cystectomy and ureterocolonic transposition has been attempted.
This surgery has been met with short-term success and a mean survival of
only four months. Complications associated with these surgeries include
chronic pyelonephritis, diarrhea, fecal incontinence, ureteral obstruction, and
hyperchloremic acidosis.
Maintaining Urinary Outflow - Surgery can also play a palliative role in
management of bladder cancer, in the case of urethral obstructive disease that
is refractory to other forms of therapy. Tube cystostomy can be performed to
relieve urine outflow obstruction in the cases of unresectable masses located
at the trigone or involving the urethra. Placement of permanent cystostomy tubes,
while seemingly radical, can allow a dog to live comfortably for a number
of weeks or months. Complications of cystostomy tube placement include
urine or infectious peritonitis, hemorrhage, and urinary tract infection.
Most recently, advances in the design and implementation of urinary stints have
allowed these devices to be used in both the dog and cat. Human coronary
artery stints may be used in the case of urethral tumor in cats, and larger stints
have been successfully deployed to restore patency to both urethra and ureters
in select canine cases.
Systemic chemotherapy is palliative at best. One study of 12 dogs that received
cisplatin for the treatment of TCC had a median survival time of 180
days. Three of the dogs had partial responses, six dogs maintained stable disease,
and the remaining three had progressive disease. Another study reported
one dog that had a partial response of 31 weeks duration. In both of these studies,
cisplatin was administered at a dose of 50mg/m 2 . Current doses range
from 50-70mg/m 2 . Doxorubicin has also been investigated as a chemotherapy
agent for TCC. In one study of 11 dogs treated with doxorubicin and cyclophosphamide,
there was a reported median survival time of 259 days.
Piroxicam is a nonsteroidal anti-inflammatory agent that acts as a non-selective
cyclooygenase inhibitor. Piroxicam may be used orally (0.3mg/kg once
daily) to provide some anti-tumor effect and palliative analgesia. The mechanism
of anti-tumor activity is thought to be blockade of PGE 2 -mediated
immunosuppression, but there is also some evidence to support cyclooxyge-
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