Development of Hypocalcemia Due to Targeted Therapies

Introduction Due to their inhibitory effect on proliferation, motility, apoptosis, and metastasis, the epidermal growth factor receptor (EGFR) inhibitor erlotinib and vascular endothelial growth factor receptor (VEGF) and EGFR inhibitor vandetanib are viable therapeutic options for the treatment of advanced non-small cell lung carcinoma (NSCLC) and thyroid cancer, respectively (1). NSCLCs and medullary or differentiated thyroid carcinomas (MTC and DTC) may show bone metastasis along with bone pain, elevated serum calcium, or elevated alkaline phosphatase levels. We present the interesting cases of two patients who were diagnosed with NSCLC and MTC with bone metastasis. Both were treated with EGFR inhibitors and presented at our outpatient clinic with hypocalcemia as a result of hypoparathyroidism.