Table 2.

Association between quintiles of plasma α-tocopherol, γ-tocopherol, and prostate cancer risk overall and by intervention arm, SELECT case–cohort study

Plasma tocopherol quintiles
12345Ptrend
α-Tocopherol≤9.83>9.83–≤11.71>11.71–≤13.70>13.70–≤16.80>16.80
 Median, mg/L8.6410.7512.6515.0120.09
 Cases/subcohort, na299/681343/656361/629375/616362/624
 Overall HRb (95% CI)1.001.07 (0.82–1.40)1.06 (0.81–1.41)1.12 (0.83–1.49)1.21 (0.88–1.66)0.24
HRb (95% CI) within intervention arms
 Placebo1.000.97 (0.56–1.68)0.91 (0.49–1.68)0.96 (0.53–1.74)0.85 (0.44–1.62)0.66
 α-Tocopherol only1.000.60 (0.35–1.03)0.72 (0.43–1.21)0.67 (0.38–1.19)0.59 (0.33–1.07)0.24
 Selenomethionine only1.001.21 (0.72–2.03)1.42 (0.79–2.55)1.69 (0.96–2.99)1.83 (0.95–3.54)0.04
 α-Tocopherol and selenomethionine1.001.72 (1.03–2.89)1.34 (0.78–2.30)1.53 (0.86–2.73)2.05 (1.15–3.67)0.06
 Any selenomethionine1.001.47 (1.02–2.13)1.44 (0.97–2.14)1.62 (1.07–2.43)2.04 (1.29–3.22)0.005
 Any α-tocopherol1.001.00 (0.69–1.46)0.96 (0.66–1.39)0.99 (0.66–1.49)1.12 (0.74–1.70)0.64
γ-Tocopherol≤0.96>0.96–≤1.47>1.47–≤2.01>2.01–≤2.76>2.76
 Median, mg/L0.661.241.732.353.41
 Cases/subcohort, na355/633361/628360/628363/629301/688
 Overall HRb (95% CI)1.001.02 (0.78–1.33)1.11 (0.84–1.45)1.13 (0.84–1.50)0.93 (0.69–1.24)0.90
HR (95% CI) within intervention arms
 Placebo1.000.84 (0.50–1.43)0.98 (0.56–1.72)0.71 (0.39–1.30)0.68 (0.37–1.25)0.17
 α-Tocopherol only1.001.24 (0.74–2.07)1.52 (0.91–2.53)1.32 (0.75–2.31)1.52 (0.88–2.60)0.16
 Selenomethionine only1.000.90 (0.52–1.55)0.97 (0.56–1.68)1.38 (0.79–2.39)0.75 (0.42–1.36)0.82
 α-Tocopherol and selenomethionine1.000.96 (0.56–1.62)0.94 (0.55–1.60)1.05 (0.62–1.76)0.77 (0.44–1.36)0.58
 Any selenomethionine1.000.93 (0.63–1.37)0.94 (0.63–1.39)1.20 (0.80–1.79)0.77 (0.50–1.16)0.64
 Any α-tocopherol1.001.15 (0.79–1.65)1.22 (0.85–1.77)1.21 (0.82–1.79)1.14 (0.77–1.69)0.48
  • aThe subcohort contains both cases and non-cases, with overlap between case and subcohort numbers.

  • bHRs based on proportional hazard regression, adjusted for PSA (continuous), family history of prostate cancer, BMI (continuous), diabetes at baseline, cholesterol (continuous), and smoking status (current smoker, former smoker, and never smoker) and mutually adjusted for γ-tocopherol or α-tocopherol (continuous). Results are also age- and race-adjusted as a result of all models being stratified by age/race groups before being weighted and combined to generate summary statistics. Overall HR also adjusted for intervention arm. The first plasma tocopherol quintiles serve as referent categories. Interaction between treatment arm and tocopherol quintiles was performed using a linear trend for quintiles in a 3 degrees-of-freedom χ2 test, with the P value for α-tocopherol being 0.20 and for γ-tocopherol being 0.27.