Clinical features of bone metastases resulting from thyroid cancer: a review of 28 patients over a 20-year period.

Bone is the second most frequent site of metastasis resulting from thyroid cancer. Many studies have investigated clinical features and prognostic factors of distant metastases stemming from thyroid cancer in Western countries. The purpose of this study was to review clinical characteristics of Korean patients with bone metastasis originating from thyroid cancer. Between January 1985 and August 2004, 28 patients with thyroid cancer were diagnosed with bone metastases at the Yonsei Severance Hospital in Seoul, Korea. Their clinical characteristics were analyzed retrospectively. Incidence of bone metastasis from follicular thyroid cancer was 6.8% (9 of 132 patients), and 0.4% (13 of 3,154 patients) from papillary thyroid cancer, with an odds ratio of 17.67 (95% confidence interval; 7.41-42). Twelve patients had no symptoms of bone metastasis. Overall mean number of metastasis sites was 2.6 +/- 1.9, and 12 patients had a solitary bone metastasis. Survival rates between the synchronous and metachronous metastasis groups were not significantly different, and the number of metastasis sites did not affect survival. However, the survival of patients that underwent curative treatment was longer than those with palliation (P = 0.0317). In Korea, the overall incidence of bone metastasis resulting from thyroid cancer was less than our expectation. Many patients were asymptomatic, and had a tendency of undergoing less aggressive or palliative treatment, even though the long-term survival of distant metastasis resulting from thyroid cancer with active treatment is relatively good. Further studies of the prognostic factors and effectiveness of various treatments of these patients are needed to enhance survival.