Analysis of treatment outcomes in patients with progressive locally advanced non-resectable and disseminated medullary thyroid cancer receiving vandetanib outside of clinical trials (Russian experience)

The study objective is to perform retrospective analysis of the efficacy and safety of vandetanib for metastatic and non-resectable medullary thyroid cancer in routine clinical practice. Materials and methods. We analyzed treatment outcomes in 46 patients treated with vandetanib. We also evaluated progression-free survival, overall survival, time to progression, and frequency of adverse events. Results. At a median follow-up time of 27.4 months (range: 2.5-106.5 months) and median duration of vandetanib therapy of 21 months, disease progression was registered in 32.6 % of cases, whereas stable disease was observed in 28.3 % of cases and 8.7 % of study participants demonstrated partial response. One patient had complete response to treatment. Almost one-third of patients (28.2 %) died, including 2 individuals whose death was not associated with cancer. The one-year and three-year progression-free survival rates were 67.3 % and 33.3 %, respectively; the two-year and five-year overall survival rates were 82.4 % and 29.4 %, respectively. The efficacy of therapy was confirmed by a 79.4 % decrease in the serum level of calcitonin after treatment initiation. Side effects were observed in 33.9 % of patients (primarily skin and gastrointestinal toxic reactions) and were easily managed in most of the cases. Eight individuals (17.4 %) required cessation of vandetanib due to adverse events. Conclusion. Our findings suggest high efficacy and acceptable safety profile of vandetanib in the treatment of progressive locally advanced non-resectable and disseminated medullary thyroid cancer. © 2020 Academic Press. All rights reserved.