54 LEARNING CURVE / Cancer Treatment
Osteosarcoma is the most common tumor of bones in dogs.
It represents 3% to 6% of all canine tumors, with an estimated 8,000 to 10,000 cases diagnosed each year in the United States.
clinical progression to define these dis- ease entities. In our experience, six subtypes are commonly observed, including diffuse large B-cell lymphoma (DLBCL), mar- ginal-zone lymphoma (MZL), Burkitt and Burkitt-like lymphoma (BL), lymphoblas- tic T-cell lymphoma (LBT), T-zone lym- phoma (TZL) and peripheral T-cell lym- phoma—not otherwise specified (PTCL) (Valli et al. 2011; Modiano et al. 2007). Other studies support the frequency with which these tumor types are observed (Valli et al. 2011). Some commonly held myths about lymphoma are especially unnerving. For example, the concept that B-cell tumors are “bad” and T-cell tumors are “terrible” means that veterinarians may be reluctant to treat any dog diagnosed with T-cell lymphoma. The lack of doc- umented prognostic significance has raised doubts about the cost-benefit and risk-benefit ratios of the diagnostic pro- cedures needed to assign any sample to its category in the WHO classification. Further, current therapeutic regimens are not tailored for lymphoma subtypes, highlighting both opportunities for improvement and additional reasons for the observed resistance to the expense and effort of classification. We have now shown conclusively that
not all T-cell lymphomas carry a poor prognosis (Modiano et al. 2007; Franz et al. 2013). Indeed, dogs with indolent T-cell lymphomas, such as T-zone lym- phomas, have a favorable prognosis and may not require aggressive therapy. What is more, aggressive therapy may be con- traindicated for these cases, potentially shortening remission times and survival. Our institution is one of several that
have instituted recommendations to clas- sify every case of lymphoma as part of our
Trends magazine, April 2013
routine practice to provide the best possible information to owners and the best thera- peutic options for their pets. To improve access to these services, we used molecu- lar data to develop new tests that can be used to distinguish clinically relevant sub- types in single-cell suspensions that can be obtained using fine-needle aspiration. This test has been licensed for devel-
opment and implementation in the diag- nostic laboratory setting and should soon help owners make decisions and improve care and quality of life for dogs with indo- lent tumors. However, access to effective therapies is needed for dogs with aggres- sive subtypes of lymphoma. We are addressing this with sup-
port from Morris Animal Foundation by exploring novel approaches that can replicate and enhance passive immuno- therapy protocols. These protocols use validated reagents that are analogous to those used to treat human patients with lymphoma (Chao et al. 2010). We expect to move these approaches to the clinic in the span of the next 1 to 3 years.
Canine Osteosarcoma: One is not as bad as the other? Osteosarcoma is the most common
tumor of bones in dogs. It represents 3% to 6% of all canine tumors, with an estimated 8,000 to 10,000 cases diag- nosed each year in the United States (Withrow et al. 1991). These tumors are highly aggressive and characterized by local invasion and destruction and by distant metastasis. In general, dogs with osteosarcoma present at stage 2b (tumor with high-grade histologic appearance outside the periosteum and no detectable metastases). Tumors spread preferentially to lungs
more commonly than to bones or other organs. Gross metastases are seen in
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