Combination chemotherapy of imatinib, vinblastine, and prednisolone in a dog with cutaneous mast cell tumor: Evaluation of treatment response withF-fluorodeoxyglucose positron emission tomography.

Abstract

An 8-year-old neutered male Maltese dog was presented with 6 palpable cutaneous masses on the neck and thorax 1 y after the surgical excision of mast cell tumors (MCT) from the mid-thoracic and right axillary regions. Before chemotherapy, the sum of the masses' diameters was 19.0 cm.F-fluorodeoxyglucose (FDG)-positron emission tomography/computed tomography (PET/CT) revealed hypermetabolic lesions within the skin overlying the ventral thorax, bilateral prescapular lymph nodes, and right axillary lymph node. The dog was diagnosed with MCT recurrence and treated with combination chemotherapy comprising imatinib, vinblastine, and prednisolone. After completion of 2 16-week chemotherapy regimens, the sum of the masses' diameters decreased to 3.6 cm. For assessment of the chemotherapy response and guidance for subsequent therapeutic plans, follow-up FDG-PET/CT was undertaken 25 d after completion of the 2nd chemotherapy regimen. It demonstrated a reduction in FDG uptake in all areas compared with that on the initial scan, except for the middle thoracic mass. After follow-up FDG-PET/CT, a 3rd chemotherapy regimen was implemented, and the dog died 416 d after the initiation of chemotherapy. There are no reports of a combination chemotherapy with imatinib, vinblastine, and prednisolone for treating canine cutaneous MCT. This case highlighted the potential therapeutic use of this combination chemotherapy for recurrent canine MCTs. Furthermore, this report indicates that FDG-PET/CT may be useful for assessing malignancy, evaluating chemotherapy responses, and establishing treatment plans for canine cutaneous MCTs. Key clinical message: Combination chemotherapy of imatinib, vinblastine, and prednisolone is a potential therapeutic regimen for recurrent cutaneous MCTs in dogs. In addition, FDG-PET/CT may be a potentially useful tool for assessing malignancy, evaluating chemotherapy responses, and guiding further therapeutic decisions.