Bone Metastases in Differentiated Thyroid Carcinoma: Resection Strategy and Other Prognostic Factors

Abstract

Purpose: Thyroid carcinomas tend to be well differentiated and non-aggressive and are generally associated with an excellent prognosis. However, the presence of distant metastases and in particular bone metastases can lead to much poorer outcomes with a median survival rate in the order of 3-6 years. For patients with thyroid carcinoma with known bone metastases it is still unclear if radical surgical for curative purposes is superior to subtotal or intralesional resection in terms of overall survival. Additionally, other factor such as visceral metastases, number of lesions, and time from diagnosis may influence survival and be used as prognostic factors. Our study aims to address these questions. Methods: This retrospective study included 72 patients undergoing surgical management of a bone lesion confirmed by pathological data to be of thyroid origin in the period between 1 July 1995 and June 2016. Surgical interventions were classified as either intralesional curettage/subtotal resection or metastasectomy/radical resection. 33% underwent metastasectomy, 66% underwent intralesional curettage. Patients’ operative reports, laboratory data, progress notes and imaging results were reviewed. Results: Of the 72 included patients, 24 (33%) underwent radical resection and 48 (66%) intralesional curettage. The mean age at time of surgery was 62.7 years-old and 44 (61%) were female and the mean follow-up was 42.9 months. 54 (75%) patients had well differentiated carcinomas and 40 (56%) also had visceral lesions. Cox regression showed that well differentiated types (HR 2.34, 1.23-4.45), solitary bone lesion (HR 2.64, 1.22-5.72), and absence of visceral disease (HR 2.90, 1.52-5.32) were all associated with better survival. The Kaplan-Meier curve for radical resection compared to intralesional resection showed a trend towards better survival with radical resection but this was not statistically significant (p=0.094). Conclusions: Our study shows that histology, advanced disease with visceral involvement and bony burden are likely to affect survival. Although not statistically significant, radical resection showed a general trend towards better survival. Our study was underpowered to detect differences of 30% in survival times with only 72 patients. In the future, efforts should be made to add patients to the cohort to detect more factors influencing survival in these patients.