55 DNA methylation markers for endometrial cancer and Google Scholar. After a series of selections, 1547 articles were excluded on the basis of their title (n=1374), abstract (n=131) and after reading the full text for not meeting the predefined inclusion criteria (n=42). This selection procedure resulted in nine articles that were included in this review. Study characteristics The characteristics of the studies included in this systematic review are summarized in Table 1. Of the nine included studies, three were carried out in Taiwan (13, 16, 24), three in the USA (25-27), two in the UK (28, 29) and one in the Netherlands (30). Accordingly, study populations of Asian, American and European origin were used. The nine selected articles were case-control studies and comprised sample sizes varying from 38 to 141 subjects. The number of EC cases and controls ranged from 21 to 50 and 17 to 120, respectively. All studies included cases of both subtypes of EC (i.e. I and II) with variable stages (stage I up to stage IV). DNA was extracted from a variety of cytological specimen, comprising cervical scrapes (13, 16, 24, 30), endometrial brushes (25, 27), vaginal swabs (28, 29), and vaginal tampons (25, 26). Studies addressing EC-specific DNA methylation detection in liquid biopsies (i.e. blood or urine) were not found. DNA methylation levels were assessed by either pyrosequencing (25-27), quantitative methylation-specific PCR (qMSP) (13, 16, 24, 30) or MethyLight PCR (28, 29), all using bisulfite converted DNA. Further details on study design and patient selection are provided in Supplementary Table 1. Four studies reported that included patients presented with postmenopausal bleeding (28, 29) or abnormal bleeding (13, 25). One study selected patients retrospectively from a population-based cervical screening cohort (30). 3
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