Medullary thyroid cancer treated with vandetanib: predictors of longer and durable response

Vandetanib is an important option to treat advanced metastatic medullary thyroid cancer. The aims of this study were to evaluate the predictors of both a longer response to vandetanib and of their outcome. Medical records of 79 medullary thyroid cancer patients treated with vandetanib in our center were analysed. Twenty-five patients were treated for <12 months, 54 were treated for >12 months and 24 of these latter were treated for <48 months (short, long and very long term treated). The median progression free survival of the long and very long term treated patients was significantly longer than in ZETA trial. When comparing the groups of short and long term treated patients the only significant difference was that these latter were less frequently previously treated with a tyrosine kinase inhibitor. However, the long term treated patients had a younger age, both at diagnosis and enrolment, that becomes statistically significant in the very long term treated patients. Inside the long term treated group, a younger age, the enrolment for symptoms and the development of adverse events were significantly correlated with a better outcome. The enrolment for symptoms remained the only statistically significant predictor of a good outcome in the very long term treated patients. In conclusion, an early treatment with vandetanib, when patients are younger, with a good ECOG performance status and a symptomatic disease, not necessarily progressing for RECIST, seem to be the best predictors of longer and durable response. Further studies are needed to confirm this evidence.