Study participants
Medical records of patients diagnosed with oral tongue cancer and cervical lymph node metastasis between January 2011 and December 2016 were reviewed. The inclusion criteria were as follows: 1) diagnosed with oral tongues cancer with cervical lymph node metastasis between January 2011 and December 2016; 2) had the pre-operative CT or MRI scans compatible with the Eclipse application (Version 15.6.05, Varian company); and 3) had the characteristics of lymph node metastasis including short-axis diameter of >1 cm, necrotic/cystic content, irregular border, and matted lymph node. The study excluded patients younger than 18 years old or non-Thais.