Table 1.

RR and 95% CIs for SCC by tertiles of plasma omega-3 and omega-6 concentrations, tumor-based analysis in all participants of the Nambour Skin Cancer Study, and in those with a personal history of skin cancer, 1997–2007

All participants (n = 1,191)Participants with previous skin cancers (n = 398)
Tertiles of plasma phospholipid concentrationsTertiles of plasma phospholipid concentrations
Fatty acidsTertile 1Tertile 2Tertile 3PtrendaTertile 1Tertile 2Tertile 3Ptrenda
Sum of omega-3, μg/mLb<48.5648.56–63.20>63.20<48.5648.56–63.20>63.20
Sum of tumors, n861311207010390
Basic RR (95% CI)c1.000.92 (0.59–1.42)0.71 (0.45–1.11)0.111.000.86 (0.51–1.44)0.63 (0.38–1.07)0.07
Multivariate RR (95% CI)d1.001.01 (0.67–1.54)0.82 (0.53–1.27)0.311.000.88 (0.53–1.47)0.66 (0.39–1.11)0.10
Linolenic acid (18:3), μg/mL<1.671.67–2.53>2.53<1.671.67–2.53>2.53
Sum of tumors, n106117114829091
Basic RR (95% CI)c1.001.06 (0.70–1.61)1.00 (0.66–1.51)0.951.000.82 (0.50–1.34)0.93 (0.57–1.51)0.86
Multivariate RR (95% CI)d1.000.96 (0.64–1.43)0.94 (0.62–1.40)0.761.000.84 (0.52–1.36)1.00 (0.62–1.63)0.89
EPA (20:5), μg/mL<9.249.24–13.28>13.28<9.249.24–13.28>13.28
Sum of tumors, n124901231017092
Basic RR (95% CI)c1.000.64 (0.42–0.97)0.58 (0.38–0.88)0.021.000.59 (0.36–0.97)0.52 (0.32–0.84)0.01
Multivariate RR (95% CI)d1.000.70 (0.47–1.06)0.67 (0.45–1.01)0.081.000.41 (0.19–0.91)0.50 (0.28–0.92)0.01
DHA (C22:6), μg/mL<36.4236.42–47.68>47.68<36.4236.42–47.68>47.68
Sum of tumors, n991031357683104
Basic RR (95% CI)c1.000.71 (0.46–1.11)0.75 (0.49–1.16)0.271.000.72 (0.43–1.22)0.69 (0.41–1.14)0.19
Multivariate RR (95% CI)d1.000.73 (0.48–1.11)0.83 (0.55–1.26)0.511.000.87 (0.51–1.49)0.99 (0.59–1.65)0.18
Sum of omega-6, μg/mLe<348.9348.90–408.01>408.03<348.9348.90–408.01>408.03
Sum of tumors, n146861051265681
Basic RR (95% CI)c1.000.83 (0.54–1.27)0.94 (0.62–1.42)0.811.000.68 (0.41–1.13)0.76 (0.48–1.21)0.27
Multivariate RR (95% CI)d1.000.81 (0.54–1.22)0.96 (0.65–1.42)0.891.000.66 (0.40–1.09)0.77 (0.48–1.22)0.29
Linoleic acid (C18:2), μg/mL<228.23228.23–273.44>273.44<228.23228.23–273.44>273.44
Sum of tumors, n143103911158662
Basic RR (95% CI)c1.001.03 (0.68–1.56)0.85 (0.56–1.29)0.441.000.98 (0.60–1.58)0.65 (0.40–1.06)0.09
Multivariate RR (95% CI)d1.000.95 (0.64–1.41)0.91 (0.61–1.36)0.651.000.98 (0.61–1.59)0.67 (0.41–1.10)0.12
AA (C20:4), μg/mL<113.45113.45–139.72>139.72<113.45113.45–139.72>139.72
Sum of tumors, n126981131097282
Basic RR (95% CI)c1.000.89 (0.59–1.36)1.05 (0.70–1.58)0.761.000.79 (0.49–1.29)0.89 (0.55–1.42)0.65
Multivariate RR (95% CI)d1.001.17 (0.78–1.76)1.15 (0.77–1.71)0.521.000.79 (0.49–1.28)0.87 (0.55–1.39)0.59
Omega-3/omega-6 ratio<0.130.13–0.16>0.16<0.130.13–0.16>0.16
Sum of tumors, n94114129759098
Basic RR (95% CI)c1.000.76 (0.49–1.16)0.61 (0.39–0.95)0.031.000.83 (0.50–1.39)0.63 (0.38–1.06)0.07
Multivariate RR (95% CI)d1.000.81 (0.54–1.22)0.67 (0.44–1.03)0.071.000.81 (0.49–1.33)0.64 (0.38–1.06)0.08

Abbreviation: AA, arachidonic acid.

  • aAll P values from two-sided tests.

  • bSum of omega-3: linolenic acid, EPA, DHA.

  • cBasic RR adjusted for age, sex.

  • dMultivariate RR adjusted for age, sex, elastosis of neck, total solar keratoses, treatment allocation.

  • eSum of omega-6: linoleic acid, AA.