Long-term follow-up and safety of vandetanib for advanced medullary thyroid cancer

Introduction: Vandetanib is indicated for adults with advanced medullary thyroid cancer (MTC). Objectives: To describe the efficacy and toxicity profile of vandetanib treatment with a maximal follow-up of 11 years at Institut Gustave Roussy/France. Methods: A review of the clinical files of the 76 MTC patients treated with vandetanib. Efficacy was estimated by markers and imaging. Results: A total of 76 patients received vandetanib. Nine were excluded from efficacy analysis because lack of morphological data. The overall (N = 76) median treatment duration was 17.6 (range: 0.7–130.6) months and the median progression-free survival (PFS) was 22.7 (95% CI, 13.9–37.3) months. In total, 21/76 (27.6%) patients were classified as long-term users because have received vandetanib for more than 48 months, with a median treatment duration of 68.1 (range: 49.1–130.6) months. For long-term vandetanib users, the objective response rate was 85.7%, the median time to best response was 27.8 (11.6.1–110) months and the median duration of response was 70.4 (38.3–127.5) (95% CI 49.5–102.8) months with a median PFS of 73.2 (95% CI, 53.1–105.6) months. Duration of response had a significant negative correlation with patient age at diagnosis (p = 0.03) and was significantly higher in patients that did not have confirmed tumor progression before treatment onset (p = 0.007). After 48 months of vandetanib use, renal failure took place in two patients and heart failure, cholecystitis, acute pancreatitis, posterior encephalopathy, and skin cancer first occurred in one patient, each. Conclusions: Our findings suggest that a substantial number of patients receiving first-/second-line vandetanib may sustain long clinical benefit and that a younger age at diagnosis and the absence of progression before treatment could be considered as predictors of durable response.