Treatment options include surgical excision, systemic therapy, radiation therapy, and palliative and supportive therapies.
Before initiating any form of therapy, clinically stage the tumor by using objective measurements. Base subsequent treatment
decisions on the results of periodic restaging as well as on the patient's tolerance to the protocol.
Figure 5. Bone scintigraphy of a 10-year-old female spayed mixed-breed dog with bladder transitional cell carcinoma. This
lateral bone scan image is of the right hindlimb and the pelvis, with cranial orientation to the right. Increased radiopharmaceutical
uptake in the diaphyses of the tibia and metatarsal area (arrows) suggests bone metastasis (confirmed with radiography and
cytology) while increased uptake in the stifle and coxofemoral joints (arrowheads) is compatible with degenerative joint disease.
In a retrospective study evaluating various therapies for bladder and urethral tumors, six of 10 dogs with apparent complete
surgical resection of their urinary bladder transitional cell carcinoma experienced a local recurrence.1 Thus, surgery can be used as an emergency therapy to relieve a partial or complete obstruction but is generally only palliative,
and owners should understand the high probability of recurrence or metastasis. Ideally, surgical excision of any malignant
tumor should be planned with the intent of achieving 1- to 2-cm margins around the visible tumor borders. This is generally
impossible in dogs with bladder transitional cell carcinoma.
A recent unpublished retrospective study found that surgical debulking resulted in a longer median survival time than diagnostic
biopsy sampling (350 days vs. 207 days, respectively).25 Nevertheless, in the context of current medical therapy, the role of surgical debulking and its impact on the prognosis
in dogs with bladder transitional cell carcinoma remain to be investigated.
Tumors located at the bladder's dorsal apex can be treated with partial cystectomy. Other surgical options include placing
permanent cystostomy catheters (see "Palliative and supportive therapies") and performing urinary diversion procedures such as a complete cystectomy combined with ureterocolonic anastomosis. These
surgical procedures have been used sporadically in veterinary patients, and while a few dogs demonstrated encouraging results,
several others suffered considerable postoperative complications.26,27 Another interesting approach under evaluation to alleviate clinical signs in dogs with urethral or prostatic neoplasia leading
to stricture is placing self-expanding metallic stents in the urethra.28
Two recent studies evaluated transurethral resection in dogs with marked urethral involvement. One study that evaluated the
use of an electrocautery loop reported a significant risk of complications in female dogs with transitional cell carcinoma,
including urethral perforation; male dogs with prostatic carcinoma benefited from this palliative approach.29 The other study used an electrovaporization technique with a rollerball electrode inserted via cystostomy in a small number
of healthy dogs.30 This study group experienced a low complication rate and demonstrated the possible applicability of this technique in treating
flat or small papillary bladder tumors.30 These minimally invasive surgical techniques warrant further investigation.
Systemic treatment of canine transitional cell carcinoma can include nonsteroidal anti-inflammatory drug (NSAID) monotherapy
or a combination of chemotherapy and an NSAID.
The NSAID piroxicam, a nonselective COX inhibitor, has been evaluated as a single agent and in combination protocols for treating
canine transitional cell carcinoma. In a prospective clinical trial, piroxicam monotherapy demonstrated an 18% overall objective
response rate (6/34), including two complete responses; many patients achieved durable stable disease (minimal or no tumor
progression for more than eight weeks).31 In addition, since moderate pain or discomfort often accompanies canine transitional cell carcinoma, piroxicam therapy tends
to subjectively improve the quality of life and facilitate micturition in most patients, even in the absence of apparent measurable
tumor response. The median survival time for the dogs in that study was 181 days.
Recent evidence suggests that COX-2 inhibition may not be the sole factor in the responses observed with piroxicam therapy
and that transitional cell carcinoma may not depend on COX-2 for survival. Specifically, it was demonstrated that there is
no association among tumor COX-2 expression, tumor PGE2 concentrations, and response to piroxicam therapy.32 Nevertheless, NSAIDs are a mainstay in treating canine transitional cell carcinoma, and ongoing studies are evaluating veterinary-approved
NSAIDs as monotherapy as well as in combination with cytotoxic chemotherapy agents. The precise mechanisms by which NSAIDs
exert their antitumor effects remain to be elucidated.