ABSTRACT
INTRODUCTION: Thyroid carcinoma is the most common endocrine neoplasm. Multimodal therapy including surgery, radioactive iodine (RAI) therapy, and indefinite suppression of thyroid-stimulating hormone has led to an 85% cure rate in differentiated thyroid tumors (DTT). Approximately 5-10% of patients will have recurrence or metastases that have the potential to become resistant to RAI treatment.1 10-year overall survival rates are reported to be 10% in these patients versus 56% in patients with RAI avid disease.2 Lenvatinib, a multi-tyrosine-kinase inhibitor (TKI), was shown to have a 65% overall response rate in addition to a significant improvement in progression-free survival (PFS), approved to treat RAI-resistant DTTs.3, 4. CASE REPORT: We are reporting a very rare case of late renal toxicity in a 68-year-old woman with a history of type 2 diabetes and metastatic RAI-resistant follicular thyroid carcinoma (Hurthle cell variant) who developed thrombotic microangiopathy 21 months after initiation of treatment. MANAGEMENT & OUTCOME: It was determined that LEN should be held, due to worsening renal function secondary to TKI-induced kidney injury. Although the patient's renal function eventually improved and returned to her baseline after discontinuation of LEN, there was marked disease progression after drug cessation. DISCUSSION: Renal toxicity is a rare adverse event (AE) that tends to occur typically within three weeks of initiation of treatment. The utilization of TKIs can lead to glomerulosclerosis, and careful considerations and precautions should be taken by clinicians who intend to initiate TKI therapy in patients with pre-existing diabetes to prevent renal toxicity.
