IGF1 and nasopharyngeal carcinoma: Serum levels of IGFBP-1 and the IGFBP-1/IGF-1 ratio significantly correlated with age (P = 0.020; P = 0.016), WHO histological classification (P = 0.044; P = 0.048), titre of EA (EB Virus Capsid Antigen-IgA) and NPC (P = 0.015; P = 0.016).