(iv) Data processing and analysis: Paired t-test (or non-parametric equivalent) will be performed to investigate differences in level of DNA methylation pre- and post- surgery. Unpaired t-test will be used to investigate difference in the level of DNA methylation between cases and controls. Correlational analysis will be used to investigate relationships between methylation status and IL-6 and TNF-α expression. Descriptive statistics will be employed to describe the changes in methylation status (i.e., if different sites in the CpG island are methylated) in the promoter region of IL-6 and TNF-α B, pre-post surgery and in the two different sampling time points of the control subjects.