Table 1. Characteristics of prospective studies on blood α- and γ-tocopherol levels and risk of prostate cancer.
| Source | Location | Study period | study type | Age, y (mean±SD) | No. of Cases | No. of matched controls | No. of participants | Measure/Range of Exposure (mg/L) | Adjustment for Covariates |
| Weinstein et al, 2012 | United States | 1993–2001 | Nested case-control study | 55–74 | 680 | 824 | 28,243 | Serum α-tocopherol: ≤12.3(Q1),>24.5(Q5); Serum γ-tocopherol: ≤1.38(Q1),>4.78(Q5) | Age, time since initial screening,, year of blood draw, study center, serum cholesterol, and serum β-carotene. |
| Gill et al, 2009 | United States | 1993–1996 | Nested case-control study | 45–75 | 467 | 936 | 96,382 | Serum α-tocopherol: 9.0(Q1),25.1(Q4); Serum γ-tocopherol:0.6(Q1),3.4(Q4) | Age, fasting hours prior to blood draw, BMI, family history of prostate cancer, and education level. |
| Key et al, 2007 | European countries | 1992–2000 | Nested case-control study | Cases:60.4(5.8) Controls:60.1(5.7) | 966 | 1,064 | 137,001 | Plasma α-tocopherol:<11.32(Q1), ≥16.80(Q5); Plasma γ-tocopherol:<0.63(Q1), ≥1.61(Q5) | BMI, smoking status, alcohol intake, physical activity level, marital status, and educational level. |
| Huang et al, 2002 | United States | CLUE * I cohort (1974–1996); CLUE II cohort (1989–1996) | Nested case-control study | CLUE I:Cases:54(9) Controls:54(9) CLUE II: Cases:66 (8) Controls:66 (8) | CLUE I 182 CLUE II 142 | CLUE I 364 CLUE II 284 | CLUE I 9,804 CLUE II 10,456 | CLUE I: Serum α-tocopherol: 9.6(Q1),15.5(Q5); Serumγ-tocopherol:1.6(Q1),3.5(Q5), CLUE II: Serum α-tocopherol:10.4(Q1),17.5(Q5); Serum γ-tocopherol:1.8(Q1),4.1(Q5) | Age, number of years since blood was drawn, disease stage at diagnosis, smoking status, and BMI. |
| Goodman et al, 2003 | United States | 1983–1997 | Nested case-control study | 45–74 | 205 | 483 | 18,314 | Serum α-tocopherol:10.67(Q1),16.80(Q4); Serum γ-tocopherol:1.75(Q1),3.57(Q4) | Age, study center at randomization, smoking status, and year of randomization. |
| Gann et al, 1999 | United States | 1982–1995 | Nested case-control study | 40–84 | 578 | 1,294 | 22,071 | Plasma α-tocopherol:8.56(Q1),14.44(Q5); Plasma γ-tocopherol: 1.25(Q1),2.53(Q5) | Physical activity, BMI, plasma total cholesterol, alcohol consumption, and multivitamin supplement use. |
| Weinstein et al, 2005 | Finland | 1985–1988 | Nested case-control study | 50–69 | 100 | 200 | 29,133 | Serum α-tocopherol:12.6(T1),15.78(T3); Serum γ-tocopherol: 0.76(T1),1.08(T3) | Age, BMI, height, smoking status, benign prostatic hyperplasia, physical activity, urban residence, education, marital status, and serum cholesterol |
| Cheng et al, 2011 | United States | 1985–2005 | Nested case-control study | Cases:60.6(5.7) Controls:60.3(5.8) | 684 | 1,441 | 18,314 | Serum α-tocopherol:11.16(Q1),32.84(Q4); Serum γ-tocopherol: 0.99(Q1),9.15(Q4) | Age, race, randomization assignment, family history of prostate cancer in first-degree relatives, alcohol consumption, smoking status, BMI, and serum cholesterol |
Abbreviations: BMI: body mass index, T:tertile, Q:quartile/quintile, SD: standard deviation. * Derived from the slogan of a campaign, “Give us a CLUE to cancer.”