Introduction
Most orbital diseases are caused by infection, inflammation, or neoplasia, and malignant orbital tumors are common in dogs and cats.1, 2 In dogs, various types of tumors with different origins occur in the orbit, including mesenchymal origin, epithelial origin, and miscellaneous origin.2 In cats, in contrast, epithelial tumors such as squamous cell carcinoma and round cell tumors such as lymphoma are more common orbital tumors, while mesenchymal tumors are less common.3 In recent years, there are some reports of a rare orbital mesenchymal tumor called feline restrictive orbital myofibroblastic sarcoma (FROMS), with clinical characteristics of eyelid restriction leading to exposure keratitis without formation of an orbital mass.4-8 However, detailed data of this tumor including the origin and tumorigenesis has not been elucidated.
Surgical resection is often selected as the first choice in the treatment of orbital tumors in dogs and cats.2, 9Other treatment options include radiation therapy and chemotherapy, which may be performed after surgery as adjuvant therapy.9, 10 In dogs with orbital tumor, cases with malignant orbital tumor treated with orbitotomy followed by adjuvant radiation therapy and chemotherapy have been reported.1 However, the efficacy of postsurgical adjuvant therapy for dogs and cats remains unclear due to a paucity of clinical reports on adjuvant therapy.10
The use of molecular targeted drugs, one type of chemotherapy, has been reported in veterinary medicine.11-13 Toceranib, which is one of the molecular target drugs, is a tyrosine kinase receptor inhibitor and has been shown to inhibit KIT, platelet-derived growth factor receptor, and vascular endothelial growth factor receptor.14-16 Clinical use of toceranib in cats for the treatment of mast cell tumors17, 18, adenocarcinoma19, 20, gastrointestinal stromal tumor21, pancreatic carcinoma22, mammary carcinoma23, squamous cell carcinoma24-26, and feline injection site-associated sarcomas (FISS)27 has been reported. However, the number of these reports in cats is fewer compared with that in dogs. In addition, there are no reports of adjuvant chemotherapy using molecular target drugs for FROMS. Herein, we present the first report of using toceranib as postsurgical adjuvant chemotherapy for the treatment of FROMS in a cat.