Bone Metastases in Medullary Thyroid Carcinoma: High Morbidity and Poor Prognosis Associated With Osteolytic...

The clinical relevance of bone metastases (BM) in advanced medullary thyroid carcinoma (MTC) is poorly described.

The objectives of this work are to describe the prevalence of BM, frequency of skeletal related events (SREs), and impact of BM morphology and SREs on prognosis, and to assess the role of antiresorptive treatment (ART).

A retrospective cohort study was conducted.

This study was conducted at 4 German referral centers.

A total of 1060 MTC patients were included.

Main outcome measures include descriptive statistics, overall survival (OS) by the Kaplan-Meier method, and risk factors by Cox proportional hazards modeling.

A total of 120 of 416 patients (29%) with metastatic MTC had BM, of which 97% had concurrent nonosseous metastases. BM occurred 2.1 years (median, range -0.1 to 20.6 years) after initial diagnosis, were multifocal in 79%, and were located preferentially in the spine (86%) and pelvis (60%). BM morphology was osteolytic in 32%, osteoblastic in 25%, and mixed in 22% of cases (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 not occurrence 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).

BM are common in metastatic MTC and most often with an osteolytic morphology and an unfavorable prognosis. The majority of SREs occur in osteolytic metastases and may be prevented by ART.