“…Apart from the selection of the detection technique and thresholds, the determination of the precise genomic positions of those CpG dinucleotides analyzed is also of great importance [ 86 ]. With regards to clinical heterogeneity, only 20.5% (9/44) of our enrolled articles mentioned the presence or absence of preoperative treatment [ 38 , 40 , 41 , 45 , 47 , 50 , 53 , 55 ]. Some studies suggested that both radiotherapy and chemotherapy can alter a patient’s DNA methylation status; therefore, the type of preoperative treatment performed should be clarified [ 87 , 88 ].…”