IGF1 and nasopharyngeal carcinoma: To investigate the association of serum levels of Vascular Endothelial Growth Factor-C (VEGFC), Vascular Endothelial Growth Factor Receptor-3 (VEGFR-3), and Insulin-like Growth Factor 1 (IGF1) with metastasis and prognosis in patients with nasopharyngeal carcinoma (NPC).