Metastatic thyroid cancer: Three extraordinary cases highlighting management principles and recent advances.

Aims: Thyroid cancer represents less than 1% of all human cancers. Metastatic thyroid cancer forms an even rarer entity. There have been a number of recent advances in treatment, namely in molecular profiling and targeted therapy. Method(s): We reviewed the latest literature as well as all cases of metastatic thyroid cancer managed at our institution over the past five years. We selected three cases that best highlight key management principles. Result(s): The first case is of a 27 year old Vietnamese male with metastatic follicular cancer on a background of thyroid lobectomy 7 years prior for follicular adenoma. He presented with symptomatic pulmonary and vertebral metastases. Retrospective review of the original lobectomy revealed a missed minimally invasive follicular carcinoma. He was commenced on systemic therapy with the tyrosine kinase inhibitor sorafenib, then changed to lenvatinib on progression. He was briefly transitioned to MEK inhibitor trametinib to facilitate tumour re-differentiation and sensitisation to radioactive iodine. The second case is of a BRAF mutation positive metastatic papillary thyroid cancer in a 57 year old East Timorese female. Her condition was complicated by DIC and SVC obstruction. Commencement of BRAF inhibitor vemurafenib resulted in clinical and haematological improvement allowing for discharge home. The third case is of a 28 year old Caucasian male with a new diagnosis of sporadic MEN2A syndrome. Diagnosis was made during an inpatient admission for back pain. Investigations revealed metastatic medullary thyroid cancer complicated by extensive bone metastases. Screening detected phaeochromocytoma and primary hyperparathyroidism. Radiotherapy for bone metastases was commenced and access for vandetanib was arranged, after considering cabozantinib through clinical trial. Unfortunately, he developed tumour-induced DIC and significant functional decline. He was discharged home with palliative care. Conclusion(s): All three cases high