Hypocalcemia During Lenvatinib Treatment for Advanced Thyroid Cancer: Clinical Features and Management in a Real-Life Setting.

Background: Several toxicities are recorded during treatment of advanced thyroid cancer (TC) with antiangiogenic drugs, including lenvatinib (LEN). Hypocalcemia was reported in registration studies, but little data are available from real-life cohorts. The aim of our study was to describe the incidence, characteristics, and the management of hypocalcemia in patients on LEN treatment. Methods: This is a retrospective cohort study of consecutive patients with advanced TC, treated with LEN for at least six months at a single tertiary center in Italy. Phosphocalcic metabolism was evaluated during treatment. Results: We included 25 patients treated for a mean of 29 ± 19 months (range 6-68 months). Hypocalcemia occurred in 6 of the 25 patients (24% [95% confidence interval 9.36-45.13%]), being of grade ≥3 in 2 of the 25 patients (8%), and recurrent in 4 of 6 patients (67%). The median time to hypocalcemia onset was 3 months (range 0.5-13 months) from starting LEN. No differences were found between patients who developed or not hypocalcemia regarding either starting/mean dose of LEN or clinicopathological characteristics. During the hypocalcemic crisis, the 2 patients with grade ≥3 hypocalcemia had low magnesium and low or inappropriately normal parathormone (PTH) levels, while 2 of 3 patients with grade 2 hypocalcemia had a secondary hyperparathyroidism. Hypocalcemia was managed with calcium oral supplementation in most cases, although up to 10% of patients required intravenous calcium treatment and transient LEN withdrawal. Conclusions: In this relatively small cohort, we observed an incidence of hypocalcemia of 24%, which is higher than that reported in the registration trial (6.9%). Both PTH-dependent and PTH-independent mechanisms explained hypocalcemia in the present cohort. Monitoring of serum calcium levels is strongly advised during the first year of LEN treatment, as hypocalcemia may be severe. More research is needed to confirm our findings and inform possible risk factors for hypocalcemia in advanced TC patients treated with LEN.