Analysis of thyroid gland invasion & indication of thyroidectomy in hypopharyngeal cancer

Abstract

In order to resect clinically occult metastasis of laryngeal carcinoma to the ipsilateral thyroid lobe and isthmus, routine ipsilateral hemithyroidectomy and isthmusectomy are commonly performed as part of the total laryngectomy procedure. However, when we reviewed surgical specimens after thyroidectomy with concomitant laryngo- pharyngectomy, the incidence of thyroid gland involvement in laryngo-pharyngeal cancer ranged from 0 to 23%. The question remains as to whether thyroid resection should be performed in the setting of no definite thyroid gland invasion on pre-operative evaluation. Thyroid gland is an important endocrine organ that regulates metabolism and maintain homeostasis. Hypothyroidism is a well known postoperative complication that occurs after laryngopharyngectomy regardless of performing thyroidectomy. Because hypothyroidism causes delayed wound healing, resulting in pharyngeal fistula, mood depression, and cardiac morbidity, thyroidectomy should be avoided if oncologically possible. In the meantime, studies conducted have focused mainly on the laryngeal cancer. However, making a decision to perform concurrent thyroidectomy on patients with hypopharyngeal cancer is important because hypopharyngeal cancer is more highly correlated with other comorbidities than laryngeal cancer. A retrospective review was conducted on the medical records from the Department of Otolaryngology at Yonsei Universitiy College of Medicine between January 1994 and December 2009. A total of 108 patients received laryngopharyngectomy as a primary treatment of primary hypopharyngeal cancer.In our study, the incidence of thyroid gland involvement was 4.6% (5 of 108 patients). The most common mechanism of invasion was direct extension through the thyroid cartilage. Thyroid cartilage invasion (p=0.034) was a statistically most significant factor in thyroid invasion. Additionally, when pyriform sinus (PS) apex invasion was noted, thyroid gland invasion should be suspected and thus consider thyroidectomy. Although the difference was not statistically significant, the prognosis of the patients with thyroid gland invasion was worse than that of the patients with no invasion.