Bone metastases in medullary thyroid carcinoma: High morbidity and poor prognosis associated with osteolytic morphology

Abstract

Context: The clinical relevance of bone metastases (BM) in advanced medullary thyroidcarcinoma (MTC) is poorly described.Objective: The objectives of this work are to describe the prevalence of BM, frequency ofskeletal related events (SREs), and impact of BM morphology and SREs on prognosis, and toassess the role of antiresorptive treatment (ART).Design: A retrospective cohort study was conducted.Setting: This study was conducted at 4 German referral centers.Patients: A total of 1060 MTC patients were included.Main Outcome Measure: Main outcome measures include descriptive statistics, overall survival(OS) by the Kaplan-Meier method, and risk factors by Cox proportional hazards modeling.Results: A total of 120 of 416 patients (29%) with metastatic MTC had BM, of which 97% hadconcurrent nonosseous metastases. BM occurred 2.1 years (median, range-0.1 to 20.6 years) afterinitial diagnosis, were multifocal in 79%, and were located preferentially in the spine (86%) andpelvis (60%). BM morphology was osteolytic in 32%, osteoblastic in 25%, and mixed in 22% ofcases (unknown: 21%). Within a median observation period of 26.6 months (range, 0-188 months)after BM diagnosis, 47% of patients experienced one or more SREs (bone radiation 50%,pathological fractures 32%), of which 42% occurred in osteolytic and 17% in osteoblastic BM(P =.047). Presence of osteolytic metastases (hazard ratio 3.85, 95% CI 1.52-9.77, P =.005) but notoccurrence of SREs was associated with impaired OS. Among the 36 patients who received ART(no ART: n = 71), SREs were significantly less frequent than in untreated patients (P =.04).Conclusion: BM are common in metastatic MTC and most often with an osteolytic morphologyand an unfavorable prognosis. The majority of SREs occur in osteolytic metastases and may beprevented by ART.