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.