SHOX2 and non-small cell lung carcinoma: Indeed, in patients with NSCLC, increased RARB2 methylation in cfDNA after chemotherapy and tumor resection was associated with disease recurrence at 9 months (Ponomaryova et al., 2013) as well as decreased levels of plasma SHOX2 methylation was associated with response to platinum-based chemo/radiotherapy (Schmidt et al., 2015).