Veterinary Medicine - January 2009 - (Page 18)

Research Updates Is hypotonic water effective as an adjuvant therapy for canine mast cell tumors? C utaneous mast cell tumors occur frequently in dogs, and successful therapy is based on wide and complete surgical excision. When the size of a tumor or its location results in incomplete resection, adjuvant therapy with radiation is recommended. A simpler alternative to radiotherapy has been to use local injections of hypotonic (deionized or distilled) water to kill residual mast cells, although previous reports in the literature have yielded conﬂicting results. In this prospective, randomized, doubleblinded, placebo-controlled clinical study from the University of Utrecht in the Netherlands, the efﬁcacy of hypotonic water as an adjuvant therapy after incomplete resection of mast cell tumors in 30 dogs was evaluated. These dogs had no regional lymph node involvement (stage 0, WHO classiﬁca- tion), and most tumors were grade II. After tumor excision, 18 dogs were treated with isotonic lactated Ringer’s solution (placebo) injected into the open wound bed, and 12 dogs received hypotonic distilled water injections. The volume of each treatment was variable, and the injections were repeated four times every seven to 10 days with the dogs sedated. A side effect of the injections with both types of ﬂuid was transient (up to 12 hours) painful muscle contractions. At one and two years after tumor excision and ﬂuid injection, no signiﬁcant differences in the recurrence-free rates (93.7% in the hypotonic group; 90.9% in the placebo group) and survival rates (93.7% in the hypotonic group; 83.3% in the placebo group) were observed between treatment groups. A poorer prognosis was observed for grade II and III tumors. The au- thors concluded that hypotonic water does not decrease local recurrence or improve survival times in dogs with solitary mast cell tumors treated by surgical excision. COMMENTARY This study’s design limited the biases (nonrandomized patient population, complete tumor resection) inherent in previous studies that showed a decrease in mast cell tumor recurrence in dogs after deionized water injection and surgery. It is interesting to note that in this study the volume of injected ﬂuid was variable and based on tissue swelling vs. using a standard amount of water. Brocks BAW, Neyens IJS, Teske E, et al. Hypotonic water as adjuvant therapy for incompletely resected canine mast cell tumors: a randomized, double-blind, placebo-controlled study. Vet Surg 2008;37(5):472-478. Delineating histologic prognostic factors for feline osteosarcoma lthough uncommon as a distinct clinical entity, osteosarcoma is the most frequently (70% to 80%) identiﬁed primary bone tumor in cats. Metastatic rates in cats (5% to 10%) are lower than those reported in dogs (80% to 90%), and wide surgical excision offers longer survival rates. This retrospective study from two European veterinary schools evaluated the effects of histologic and clinical characteristics on prognosis for feline osteosarcoma, along with a histologic comparison to phenotypically similar canine osteosarcoma lesions. The authors reviewed the medical records of 62 cats (1994 to 2004) with histologically conﬁrmed osteosarcoma and 22 dogs (1985 to 1999) with histologically conﬁrmed skeletal osteosarcoma of the same location and subtype that corresponded to 22 of the feline skeletal osteosarcoma cases. The study results revealed that the cats exhibited more axial (25) than appendicular (15) lesions and more skeletal (40) than extraskeletal (22) tumors. Results also revealed that feline osteosarcoma was most frequently identiﬁed in the maxilla (seven cases) and interscapular region (ﬁve cases) and that feline skeletal osteosarcoma was A histologically similar to canine skeletal osteosarcoma. The cats had a tumor recurrence rate of 44% after surgery and a metastatic rate of 10%. A poorer prognosis was seen in cats with incomplete surgical resection, increased histologic grade, and increased mitotic index. Although vascular invasion by osteosarcoma was high in the cats in this study (82%) and is associated with a high-grade tumor and poor prognosis in dogs with osteosarcoma, it was not a signiﬁcant prognosticator for feline osteosarcoma. The authors concluded that feline and canine skeletal osteosarcoma share similar histologic characteristics yet different prognostic characteristics. COMMENTARY In cats, axial osteosarcoma carries a poorer prognosis than appendicular or extraskeletal forms, probably because of difﬁculty in surgical excision. From this report, histologic analysis of tissues in cats with osteosarcoma will aid clinicians in providing a prognosis for owners, especially if incomplete surgical resection (unclean margins) occurs. Because feline osteosarcoma lesions have not been as frequently described as canine osteosarcoma lesions, reporting survival rates for patients in this study would have been beneﬁcial. Dimopoulou M, Kirpensteijn J, Moens H, et al. Histologic prognosticators in feline osteosarcoma: a comparison with phenotypically similar canine osteosarcoma. Vet Surg 2008;37(5):466-471. 18 January 2009 VETERINARY MEDICINE

Table of Contents Feed for the Digital Edition of Veterinary Medicine - January 2009

Veterinary Medicine - January 2009 Contents Leading Off Letters Research Updates Idea Exchange A Modified Subconjunctival Enucleation Technique in Dogs and Cats Local and Regional Anesthesia Techniques Author Guidelines Product Preview CE Form/Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - January 2009

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