Metastases of well-differentiated thyroid cancer to the gastrointestinal system

Abstract

Background: The incidence of distant metastases at the time of initial presentation of well-differentiated thyroid cancer is approximately 4%. During the course of treatment and follow-up, the prevalence of distant metastases ranges from 2% in low-risk patients up to 33% in high-risk patients. When present, distant metastases occur primarily in the lungs and, to a lesser extent, in bones. Of all sites for distant metastasis, gastrointestinal metastases of thyroid cancer are very uncommon and account for 0.5-1% of all distant metastases.

Summary: Indications of metastases to the gastrointestinal system can be overlooked with traditional total body radioisotope scans that image the abdomen, including both diagnostic and posttherapy scans, because of the confounding presence of physiologic enteric radioactivity. When suspected in high-risk patients, other imaging procedures such as computed tomography, magnetic resonance imaging, and PET-computed tomography should be considered. This communication will review thyroid cancer metastases to the gastrointestinal system in regard to occurrence rate, diagnosis, and treatment.

Conclusions: Because of the extreme rarity of patients with metastases of thyroid cancer to the gastrointestinal tract, long-term follow-up data as well as information on prognosis are very limited. Aggressive management may provide symptomatic relief or palliation, but cure is unlikely once widespread metastases supervene. Attempts at complete or near-complete surgical resection of the metastases invading the digestive tract, followed by 131-I treatment, offer the best opportunity for improvement but will only rarely result in cure in selected patients.