Table 4. Odds ratios for incident breast cancer in relation to quartiles of plasma oestradiol, testosterone and SHBG, Breakthrough Generations Study, United Kingdom.
|
Plasma hormone level, quartilesa |
|||||
|---|---|---|---|---|---|
| |
1st |
2nd |
3rd |
4th |
|
| Sex hormone or SHBG level/adjustment factors | ORc (95% CI) | ORc (95% CI) | ORc (95% CI) | P-value trendb | |
|
Oestradiol | |||||
| Multivariatec | 1.00 | 1.18 (0.67–2.09) | 1.51 (0.83–2.75) | 2.07 (1.11–3.84) | 0.002 |
| +Percentage densityd |
1.00 |
1.21 (0.68–2.16) |
1.49 (0.81–2.75) |
2.03 (1.08–3.81) |
0.004 |
|
Free oestradiol | |||||
| Multivariatec | 1.00 | 1.32 (0.74–2.36) | 1.72 (0.95–3.13) | 2.42 (1.27–4.61) | 0.001 |
| +Percentage densityd |
1.00 |
1.46 (0.81–2.63) |
1.78 (0.97–3.27) |
2.48 (1.29–4.78) |
0.001 |
|
Testosterone | |||||
| Multivariatec | 1.00 | 1.34 (0.75–2.37) | 1.42 (0.79–2.52) | 2.11 (1.20–3.70) | 0.007 |
| +Percentage densityd |
1.00 |
1.21 (0.67–2.18) |
1.36 (0.76–2.44) |
2.01 (1.14–3.54) |
0.009 |
|
Free testosterone | |||||
| Multivariatec | 1.00 | 1.47 (0.82–2.64) | 1.82 (1.01–3.28) | 2.07 (1.15–3.74) | 0.001 |
| +Percentage densityd |
1.00 |
1.53 (0.85–2.76) |
1.87 (1.03–3.40) |
2.15 (1.18–3.91) |
0.001 |
|
SHBG | |||||
| Multivariatec | 1.00 | 1.10 (0.63–1.90) | 0.86 (0.48–1.56) | 0.64 (0.35–1.20) | 0.055 |
| +Percentage densityd | 1.00 | 1.11 (0.63–1.95) | 0.74 (0.40–1.37) | 0.58 (0.31–1.10) | 0.024 |
Abbreviations: CI=confidence interval; OR=odds ratio; SHBG=sex hormone-binding globulin.
1st, 2nd, 3rd, 4th quartile, respectively, oestradiol: <13.18, 13.18–18.86, 18.87–29.38, >29.38 pmol l−1; free oestradiol: <0.29, 0.29–0.44, 0.45–0.69, >0.69 pmol l−1; testosterone: <0.40, 0.40–0.63, 0.64–0.91, >0.91 nmol l−1; free testosterone: <0.0055, 0.0055–0.0087, 0.0088–0.0138, >0.0138 nmol l−1; SHBG: <31.30, 31.30–43.45, 43.46–59.10, >59.10 nmol l−1.
On the basis of Wald test on log base 2 transformation of respective sex hormone or SHBG value.
Covariates: year of entry to the study (⩽2005, 2006, 2007, ⩾2008); age at entry (5-year age groups); blood in post (0–1, 2, ⩾3 days, not known); years breast cancer free in study (0–6); body mass index (kg m−2) (continuous); parity (nulliparous; age at first birth <25 years/1–2 children; age at first birth <25 years/⩾3 children; age at first birth 25–29 years/1–2 children; age at first birth 25–29 years/⩾3 children; age at first birth ⩾30 years/1–4 children); family history of breast cancer (yes, no); age at menarche (⩽12, 13, 14, 15–20, not known); age at menopause (<45, 45–49, 50–54, ⩾55, not known); years of postmenopausal hormone therapy use (never, <2, 2–5, 6–9, ⩾10, not known); alcohol units (0, <5, 5–14, ⩾15 g per day, not known); laboratory batch.
Further adjustment for mammographic percentage density quartiles.