Removing masses of the hind limbs isn't always simple. Small malignant masses, large masses and masses over bony prominence, in particular, can cause a problem. Removal of malignant masses of the hind limb with adequate margins of normal skin often leaves a skin defect that may be impossible to close without excessive tension. Since this type of mass is easily removed in other areas of the body, we are reluctant to consider more involved procedures that require more planning, surgical time, and expense.

For some of those cases, the caudal epigastric axial pattern flap should be considered. While performing this flap requires preoperative planning and more surgical time than direct closure, it's reliably results with uncomplicated healing in 10 to 14 days is often more ideal. This avoids weeks of bandaging for either delayed incisional healing or dehiscence associated with direct closure under tension.

Pavletic, MP: Atlas of Small Animal Reconstructive surgery. Philadelphia, WB Saunders, 1980.

Pavletic, MP: Pedicle Grafts. In Slatter, D (ed): Textbook of Small Animal Surgery, 3^rd ed. Philadelphia, WB Saunders, 2002.

New developments in the treatment of canine transitional cell carcinoma (TCC) of the urinary bladder - New use for an old drug

By Andy Abbo DVM, MS, DACVIM - Oncology, New England Veterinary Oncology Group

Transitional cell carcinoma (TCC) of the urinary bladder is the most common cancer of the canine urogenital tract and is challenging disease to manage that arises from malignant transformation of epithelial cells lining the urinary bladder, urethra, prostatic ducts and renal pelvis.

Treatment of TCC is directed at both local and distant control of disease with most dogs succumbing to failure of local disease control resulting in urinary tract obstruction. Treatments evaluated to date have limited response rates and efficacy in controlling both local and distant disease.

Surgery is generally not considered feasible due to most tumors being either diffusely affecting the urinary bladder at diagnosis or trigonal location; however, tumors located in the apex may be surgically excised. These excisions can be performed if there is no evidence of distant metastasis, though relapse is often noted within a 3-to-6-month period without adjunct therapy.

Relapse may occur due to the "field effect," which states that carcinomas (often of transitional cell origin) develop within a contiguous field of pre-neoplastic cells. These cells already possess genetic alterations associated with the process of carcinogenesis, which leads to a sub-clone of cells that ultimately develop into invasive carcinoma. The role of radiation therapy in the management of TCC is not well defined at this time.

Medical management with COX inhibitors and IV chemotherapy has been the mainstay of therapy with response rates reported of 18-38 % and survival times ranging from 6-12 months. However, some of the longest surviving dogs, in my opinion, receive multiple different chemotherapy protocols and surgery is combined ONLY if localized disease is noted in a location that allows for safe resection (i.e. apical or mid body location). COX inhibitors such as Piroxicam, Carprofen and Deramaxx have been evaluated, have anticancer effects and are well tolerated. Other NSAIDs are expected to yield similar responses but have not been fully evaluated in the veterinary literature.

In a recently published prospective clinical trial to evaluate the efficacy of single agent vinblastine for the treatment of canine TCC¹, researchers at the Purdue Comparative Oncology Program found that vinblastine has antitumor activity against TCC  both in vivo and in vitro.

Vinblastine has efficacy when used either as a single agent or in combination protocols when used to treat humans with the muscle invasive form of TCC which is similar in biological behavior to the naturally occurring disease in canines.  In laboratory studies, vinblastine was shown to have potent anti-proliferative effects against canine TCC cells in vivo² and vinblastine concentrations that inhibited cell proliferation by 50% in canine TCC cell lines were lower than serum concentrations reported with standard in vitro dosing further supporting the use of vinblastine in the treatment of canine TCC. 

Twenty-eight privately owned client dogs were enrolled in this trial and tumor responses were noted in 10 dogs (36% partial remission, 14% progressive disease). No complete responses were noted. The median survival time was 147 days (range, 28-476 days) from first vinblastine treatment to death and 299 days (range, 43-921 days) from diagnosis to death with a median progression free interval of 122 days (28-399 days).

This new data supports that vinblastine as a single agent is a viable option for pet dogs with clinical responses noted and limited toxicity. Vinblastine also has the advantage of being associated with less expense to clients than other historical agents. Interestingly many of the dogs enrolled in this study had failed previous therapy with other agents supporting its use as both a primary and rescue agent. Further studies will need to be performed to evaluate the combination of vinblastine with COX inhibitors and other chemotherapy agents.