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Table 1 Characteristics of the nested case-control studies included in the meta-analysis

From: Blood DNA methylation and breast cancer risk: a meta-analysis of four prospective cohort studies

Characteristics Melbourne Collaborative Cohort Study European Prospective Investigation into Cancer and Nutrition (Italy) European Prospective Investigation into Cancer and Nutrition (IARC) Prostate, Lung, Colorectal and Ovarian Screening Trial
Acronym MCCS EPIC-Italy EPIC-IARC PLCO
Reference (17) (18) (19)
Location Australia Italy Germany, Greece, Italy, Spain, The Netherlands, and the UK US
Methylation array used HM450K HM450K HM450K EPIC
Number of subjects, n
 Controls (N = 1926) 409 248 423 805
 Cases (N = 1703) 409 248 423 583
Age at blood draw (years), mean (SD) 56.7 (7.9) 52.2 (7.2) 52.2 (9.0) 62.2 (5.2)
Time from blood draw to diagnosis in cases
 Median (IQR) 7.7 (4.4., 11.1) 6.55 (2.5, 10.6) 7.7 (5.0, 10.3) 8.4 (5.6, 10.5)
 Average (SD) 7.6 (3.9) 6.7 (4.4) 7.5 (3.2) 7.9 (3.5)
ER status, n (%)
 Positive 297 (72.6) 147 (59.3) 350 (82.7) 411 (70.5)
 Negative 103 (25.2) 30 (12.0) 73 (17.3) 78 (12.9)
Stage, n (%)
 Early 246 (60.1) 71 (28.6) 207 (48.9) 337 (57.8)
 Late 141 (34.5) 40 (16.1) 95 (22.5) 183 (31.4)
  1. SD standard deviation, IQR interquartile range, ER estrogen receptor
  2. Stage: a cancer was considered an early stage if it was classified as localized (EPIC-Italy, EPIC-IARC) or stage I (MCCS, PLCO). A cancer was considered late-stage if it was classified as regional or metastatic (EPIC-Italy, EPIC-IARC) or stages II, III, or IV (MCCS, PLCO)