ERCC1 and oral cavity cancer: Furthermore, the subgroup analysis of variables showed that patients with advanced ages (40–80 years), advanced stages (stage IV), highly differentiated tumors (grades 1 and 2), low BMIs (underweight/normal), social habits (tobacco smoking, alcohol consumption, betel leaf chewing), oral cavity cancers, and hypopharyngeal cancer who received CCRT alone or five cycles of cisplatin are at high risk of developing ERCC1-mediated cisplatin resistance as ERCC1 was found to be significantly increased in these patients.