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Higher Rates of Bone Metastases and Increased Risk of Death in Follicular and Medullary Thyroid Cancer

Key Points

  • Of the 30,063 patients with thyroid cancer, 1,173 (3.9%) developed bone metastases and 1,661 patients (5.5%) developed a skeletal-related event.
  • Compared with papillary thyroid cancer, the likelihood of developing bone metastases or a skeletal-related event was higher in follicular and medullary thyroid cancer.
  • The occurrence of a bone event was associated with greater risk of overall and disease-specific mortality. Bone events were a poor prognostic indicator, even when compared with patients with other distant metastases. 

In the largest-known study on bone metastases in thyroid cancer, researchers at the University of Michigan Comprehensive Cancer Center found that patients with follicular and medullary thyroid cancer had the highest rate of cancer-related bone lesions and fractures and an increased risk of death. Their findings were published by Choksi et al in the Journal of Clinical Endocrinology and Metabolism.

“We know that metastases are bad. But patients in our study who had bone metastases had a worse survival rate compared to patients who had metastases at other distant sites,” said Megan Haymart, MD, Assistant Professor of Medicine at Michigan Medicine and one of the researchers on the study. “This suggests that bone metastases are a uniquely poor prognostic indicator.”

However, patients with localized or regional thyroid cancer—without metastases—have an excellent prognosis, added Palak Choksi, MD, Assistant Professor of Medicine at Michigan Medicine and lead author of the study.

Study Findings

The study looked at all forms of thyroid cancer—medullary, follicular, papillary, and anaplastic. The study was based on SEER-Medicare data and involved approximately 30,000 patients, 70% of whom were Caucasian women with an average age of 64. The high percentage of women in the study reflects the fact that thyroid cancer is three times more common in women than in men.

Of the 30,063 patients with thyroid cancer, 1,173 (3.9%) developed bone metastases and 1,661 patients (5.5%) developed a skeletal-related event (SRE). Compared with papillary thyroid cancer, the likelihood of developing bone metastases or an SRE was higher in follicular and medullary thyroid cancer. The occurrence of a bone event was associated with greater risk of overall and disease-specific mortality. Bone events were a poor prognostic indicator, even when compared with patients with other distant metastases.

Previous studies that mainly looked at differentiated thyroid cancer and bone metastases had a significantly smaller sample size and were largely from single institutions that enrolled patients with differentiated thyroid cancers.

Currently, the data on medications for skeletal metastases in thyroid cancer has been extrapolated largely from breast cancer and other cancers that often metastasize to bone, said Dr. Choksi. Very little research has focused specifically on the use of medications to treat thyroid cancer with skeletal complications.

“Patients with thyroid cancer have been understudied,” said Dr. Haymart.

This research will help tailor treatment and management, and it's especially useful for patients with high-risk thyroid cancer—medullary and follicular.

“Now that we have identified that certain thyroid cancers are at a higher risk for skeletal-related events, we can appropriately design studies looking at drugs to see which medication could prevent or effectively treat such complications,” said Dr. Choksi. “Through our study, we want other doctors to be aware that there is a higher likelihood of skeletal lesions or fractures in this high-risk population.”

The authors acknowledge that there are limitations to the study, and the applicability of the research to younger patients is reduced. “Despite this limitation, our study parallels on a larger scale what other smaller studies have shown in a varied population group,” said Dr. Choksi.

For high-risk patients, future research is needed to show how to prevent and treat bone metastases. Studies have already shown that denosumab and bisphosphonates are beneficial for patients with other cancers of the bone. The researchers suspect these drugs may also be beneficial for patients with thyroid cancer and bone metastases, although additional prospective studies are need.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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