Aberrant DNA methylation is one of the most classical events that occurs during lung cancer development.36 Many studies have shown altered methylation patterns in lung cancer, indicating roles of epigenetic biomarkers and therapeutic targets.37-39 Earlier study by Zhu et al40 focused on the methylation patterns of Wnt antagonists, showing the association of methylated SFRP5 with shortened progression-free survival under EGFR-TKI treatment, but not with IR to TKI. The gene discussed is SFRP5; the disease is lung cancer.