TABLE 3.
Association between total folate intake and postmenopausal breast cancer risk, by tumor characteristics1
| Quartile of 10-y total folate intake |
||||||
| 1 | 2 | 3 | 4 | P for trend2 | P for difference3 | |
| Tumor size | ||||||
| Cases with tumors <1.5 cm | 82 | 89 | 88 | 76 | ||
| Multivariable-adjusted RR (95% CI) | 1.00 | 1.09 (0.80, 1.49) | 0.97 (0.71, 1.31) | 0.84 (0.60, 1.17) | 0.20 | |
| Cases with tumors ≥1.5 cm | 85 | 72 | 84 | 70 | ||
| Multivariable-adjusted RR (95% CI) | 1.00 | 0.83 (0.60, 1.15) | 0.89 (0.65, 1.22) | 0.69 (0.49, 0.98) | 0.07 | 0.57 |
| ER status | ||||||
| Cases with ER+ status | 139 | 132 | 151 | 136 | ||
| Multivariable-adjusted RR (95% CI) | 1.00 | 0.95 (0.74, 1.21) | 0.99 (0.78, 1.26) | 0.88 (0.68, 1.14) | 0.43 | |
| Cases with ER− status | 24 | 27 | 26 | 11 | ||
| Multivariable-adjusted RR (95% CI) | 1.00 | 1.08 (0.61, 1.90) | 0.95 (0.54, 1.68) | 0.38 (0.18, 0.80) | 0.02 | 0.02 |
Multivariable relative risks (RRs) and associated 95% CIs were estimated by using a Cox regression model adjusted for age (y), race (white or other), family history of breast cancer (none, 1 affected mother or sister, or ≥2 affected mother or sisters), mammography within 2 y preceding baseline (no or yes), history of breast biopsy (no or yes), age at menarche (≤11, 12, 13, or ≥14 y), age at first birth (nulliparous, or ≤19, 20–24, 25–34, or ≥35 y), age at menopause (≤44, 45–49, or ≥50 y), years of combined estrogen and progestin postmenopausal hormone use (never or <1, 1–4, 5–9, or ≥10), BMI (in kg/m2; <25, 25 to <30, or ≥30), height (<62, 62 to <65, 65 to <68, or ≥68 in.; 1 in. = 2.54 cm), total physical activity (none, 1–3 tertiles of metabolic equivalent hours/wk), and alcohol intake in the past year (<1.5, 1.5–4.9, 5.0–9.9, or ≥10 g/d). We additionally adjusted for total energy intake (kcal/d) in analyses of dietary and total nutrient intakes. Total folate intake was calculated as the sum of diet over year before baseline plus the 10 y-average from supplements. ER, estrogen receptor.
Calculated by modeling categories of total folate as a single ordinal variable in a Cox regression; a Wald test was used to obtain a P value.
Tests for differences were calculated by excluding all noncases and fitting a multivariable unconditional logistic regression model, with comparison of case groups by tumor characteristic; a Wald statistic was used to obtain a P value.