Four MTCs harbored the somatic RET mutation c.2753T>C, p.Met918Thr. The best clinical response was seen in a MEN2A patient. PK characteristics were consistent with phase I data. One patient exhibited extensive toxicity accompanying elevated everolimus plasma concentrations....The MEN2A MTC patient showed the best response upon everolimus therapy. Apart from the treatment effect, the RET c.1858T>C, p.Cys620Arg mutation has been associated with a less aggressive phenotype compared to other MEN2A-related mutations such as the c.2753T>C p.Met918Thr mutation or one of the classic mutations in exon 11 at codon 634...