Objective: The purpose of this study was to retrospectively analyze the trends in RT among dogs and cats treated at the S Animal Cancer Center in Korea from 2020 to 2023. Methods: A retrospective analysis was conducted on 376 animals (308 dogs and 68 cats) receiving RT for various tumors. Data collected included species, breed, sex, age, weight, tumor location, tumor type, RT protocols, and concurrent treatments. Results: The number of patients receiving RT increased from 59 in 2020 to 120 in 2023, reflecting a 103.4% increase over the study period. Sinonasal, intracranial, oral, genitourinary, and skin tumors were the most common, with stereotactic RT being most commonly used for sinonasal and intracranial tumors. Of the patients, 175 (46.5%) received RT alone, 96 (25.5%) with chemotherapy, 64 (17%) with surgery, and 41 (10.9%) with both surgery and chemotherapy. Thirty-one patients (8.2%) underwent multiple RT sessions, primarily for sinonasal tumors (11 cases). Conclusions and Relevance: This study provides the first systematic analysis of RT use in companion animals in Korea and establishes a foundational dataset for future work in veterinary radiation oncology. The findings highlight the growing clinical use of RT and underscore the need for further research to optimize treatment protocols and evaluate patient outcomes in Korean veterinary oncology.

A 3-year-old spayed female Russian blue cat was presented for dyspnea, nasal discharge, and stertorous breathing. Plain thoracic radiography revealed no specific findings. Computed tomography (CT) was performed to differentiate upper airway tract disorders. It revealed the presence of an iso-attenuating mass measuring 10.0 × 7.9 × 15.6 mm, with mild homogeneous contrast enhancement occupying the rostral nasopharynx. The mass was surgically debulked via a longitudinal incision in the soft palate. Histopathological and immunohistochemistry analysis of the surgically excised mass revealed CD3–/ CD79a+ B cell lymphoma with an incomplete margin. The patient underwent hypofractionated radiation therapy, receiving a total of 36 Gray (Gy) in 6 Gy fractions over a six-week period. A follow-up CT examination was performed after 27 months of irradiation and the patient was confirmed to have achieved a complete response. There were no complications related to irradiation. The patient was alive for 40 months without recurrence. This study suggests that hypofractionated radiation therapy combined with surgical debulking could be considered as a treatment option for feline nasopharyngeal lymphoma.