Fig. 2

Association between LINE-1 hypomethylation levels and the selected clinical parameters. The mean LINE-1 hypomethylation levels for the various groups are compared using Student’s t-test. a Laryngeal cancer: statistically significant differences are found between LINE-1 hypomethylation levels and age as well as between LINE-1 hypomethylation levels and tumor size. b Hypopharyngeal cancer: no differences are noted for any of the clinical characteristics. c Oropharyngeal cancer: statistically significant differences are found between LINE-1 hypomethylation levels and HPV status (positive versus negative). d Oral cavity cancer: statistically significant differences are found between LINE-1 hypomethylation levels and recurrence events (positive versus negative). The mean and standard deviation are also indicated. *P < 0.05