OBJECTIVES: The purpose of this study was to determine the survival time and overall benefits in dogs with bilateral thyroid carcinomas after performing unilateral thyroidectomy.
METHODS: Retrospective analyses of eight dogs with bilateral thyroid tumors treated with unilateral thyroidectomy at the Azabu University Veterinary Teaching Hospital Oncology Department between April 2000 and December 2008. Unilateral thyroidectomy was performed by removing the larger of the bilaterally formed tumors. The median survival period was calculated using the Kaplan-Meier product limit method.
RESULTS: The mean excised tumor size was 4.6 cm, ranging from 3 to 8 cm, while the non-operated mean tumor size was 2.5 cm(2-4 cm). The Kaplan-Meier analysis determined a median survival time of 593 days, ranging up to 1139 days. Five dogs received adjuvant chemotherapy, while one underwent palliative radiotherapy on the progressive non-resected tumor. There were neither local recurrences nor tumor-related deaths. Only one dog developed metastasis in the lung.
CLINICAL SIGNIFICANCE: This is the first study performed exclusively on bilateral thyroid carcinomas to assess the effects of unilateral thyroidectomy. Unilateral thyroidectomy(i. e., removal of the larger tumor, while leaving the non-excised tumor[<4cm])in place prolonged the median survival time to nearly 20 months without increasing the risk of complications as seen in bilateral-thyroidectomy.