CALCA and nasopharyngeal carcinoma: Additionally, in frequent patients it is almost impossible to discriminate NPC from NPA/B individuals on the basis of only C-triol and 7-KC levels (Klinke et al. 2015; Romanello et al. 2016; Reunert et al. 2016; Pagan et al. 2015; Amraoui et al. 2014; Lin et al. 2014).