Spinal metastases due to thyroid carcinoma: an analysis of 202 patients

Spinal metastases (SMs) due to thyroid cancer (TC) are associated with significantly reduced quality of life. The goal of this study is to analyze the clinical manifestations, presentation, and treatments of TC SMs, and to describe specific features of SMs associated with different TC types.

A retrospective analysis of 202 TC SM patients treated at Medstar Washington Hospital Center (37) and collected from the literature (165) was performed.

The mean age of patients with SMs was 56.9±14.7 years, and the female-to-male ratio was 2.1:1. Of all patients, 29% (28% of follicular thyroid cancer [FTC] and 37% of papillary thyroid cancer [PTC]) had SMs only. Twenty-nine percent of all patients and 54% of patients with single-site SMs had neither bone non-SMs nor solid organ metastases at the time of presentation. Thirty-five percent of patients had SMs as an initial presentation of TC. TC patients presenting with SMs had a lower rate of other bone and visceral involvement compared with patients whose SMs were diagnosed at the time of thyroid surgery or during follow-up (p<0.05). SMs were more often the initial manifestation of FTC (41% vs. 24%), while PTC SMs were more commonly diagnosed after TC diagnosis (76% vs. 59%; p<0.05). PTC SMs were more frequently diagnosed as synchronous (63% vs. 36% in FTC) versus FTC SMs that developed as metachronous metastases (64% vs. 37% in PTC; p<0.01). All FTC SMs developed within 82 (0-372) months and all PTC SMs within 35 (0-144) months (p<0.01). In FTC SMs as TC manifestation, solid organ metastases involvement was less common than in FTC SMs that were found after TC diagnosis (34% vs. 67%; p<0.01); multisite FTC SMs compared to solitary FTC SMs were associated with the development of other bone nonspinal metastases (82% vs. 30%; p<0.01) and solitary organ metastases (65% vs. 41%; p<0.01). These correlations were not observed in PTC SMs. FTC patients often had neural structure compression (myelopathy/radiculopathy; 72% vs. 36% in PTC), while PTC patients frequently were asymptomatic (38% vs. 5% in FTC; p<0.01). FTC SMs more commonly were (131)I-avid (p<0.01). FTC patients required surgery more frequently (72% vs. 55% in PTC; p<0.05).

Our study reveals that a significant part of TC SMs patients have solitary spinal involvement at the time of presentation and may be considered for aggressive treatment with the intention to improve quality of life and survival. FTC SMs and PTC SMs appear to have distinct presentations, behavior, and treatment modalities, and should be categorized separately for treatment and follow-up planning.