Treatment options for canine cutaneous mast cell tumors - Veterinary Medicine
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Treatment options for canine cutaneous mast cell tumors
You'll likely encounter patients with these neoplasms in your practice. Luckily, many treatment options are available, such as surgery, radiation therapy, and chemotherapy—and new treatments are on the horizon.



Contrary to the success in treating localized disease with surgery alone or with adjuvant therapies, the effective management of surgically nonresectable macroscopic disease or advanced distant metastatic mast cell disease remains problematic. In these patients with extensive disease, the intent of therapy is no longer curative. Rather, therapy should be focused on reducing tumor burden, improving quality of life, and prolonging survival times. Therapies with these defined goals are categorized as palliative. Several palliative treatment options exist for managing noncurable mast cell tumors in dogs, including systemic chemotherapy, palliative radiation, and intralesional triamcinolone.

Systemic chemotherapy

TABLE 3. Systemic Chemotherapy for Macroscopic Mast Cell Tumor Burden
Although potentially useful as an adjuvant to surgery, systemic chemotherapy has been traditionally indicated to treat metastatic and nonresectable mast cell tumors. Several studies have identified chemotherapeutic regimens possessing marginal to moderate therapeutic efficacy for treating advanced mast cell tumors in dogs (Table 3). The response rates, duration of remission, disease-free intervals, and survival times of dogs with metastatic or nonresectable mast cell tumors can be quite variable, with a subset of patients maintaining a high quality of life for an extended period. For this reason, treatment options for patients with advanced disease should not be limited solely to euthanasia.

Most chemotherapeutic regimens are easy to administer, but specialized equipment is recommended (a biologic safety cabinet) to minimize unnecessary and hazardous exposure to chemotherapeutic agents. In addition, familiarity with the handling, safety, side effects, and administration of each anticancer agent should be considered a necessity before instituting chemotherapy.

Radiation of macroscopic tumors: Curative and palliative fractionation schemes

FIGURE 7. This male Labrador retriever is suffering from aggressive multicentric cutaneous mast cell disease. Therapeutic options, including palliative radiation therapy and systemic chemotherapy, provided a partial clinical response and quality-of-life improvement. FIGURE 8. Intralesional therapy with triamcinolone may be useful in reducing the size of mast cell tumors before surgical resection or for shrinking macroscopic tumors for palliative purposes.
When cytoreductive surgeries are not an option for cutaneous mast cell tumors, using radiation therapy alone or in conjunction with other adjuvant therapies may be considered (Figure 7). In one study, 21 dogs with macroscopic tumor burden were treated with curative-intent radiation therapy.19 As would be expected, the initial tumor volume affected the duration of response to radiation therapy. Dogs with tumor volumes 9 cm3 or less had a significantly longer disease-free interval (about 20 months) than dogs with tumor volumes 10 cm3 or greater (about four months) had. While dogs with larger tumors had a shorter duration of response, the results from this study support the role of curative-intent radiation therapy for managing dogs with macroscopic tumor burden.

Although curative-intent radiation may have a role in treating macroscopic disease, a large time and financial commitment is required of pet owners. In some situations, palliative radiation therapy may be considered a more appropriate treatment option. In comparison to curative-intent treatment regimens, palliative radiation involves administering larger doses of radiation at less frequent intervals. A typical palliative protocol would be administering one large dose of radiation every week for four consecutive weeks.


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