Table 1.
Associations of extent of mammographic breast density with breast cancer risk by levels of benign histologic impression
| Low Density | Medium Density | High Density | p-valuea | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Characteristic | N | Obs | Exp | SIR (95% CI) | N | Obs | Exp | SIR (95% CI) | N | Obs | Exp | SIR (95% CI) | |
| Histologic Impression | |||||||||||||
| NP | 699 | 30 | 40.07 | 0.75 (0.50, 1.07) | 1586 | 99 | 80.27 | 1.23 (1.00, 1.50) | 1247 | 95 | 56.69 | 1.68 (1.36, 2.05) | <0.001 |
| PDWA | 364 | 31 | 22.15 | 1.40 (0.95, 1.99) | 1104 | 113 | 58.76 | 1.92 (1.58, 2.31) | 801 | 78 | 43.50 | 1.79 (1.42, 2.24) | 0.27 |
| AH | 69 | 12 | 3.53 | 3.40 (1.76, 5.93) | 231 | 41 | 11.77 | 3.48 (2.50, 4.73) | 170 | 29 | 8.92 | 3.25 (2.18, 4.67) | 0.96 |
Standardized incidence ratios and corresponding 95% confidence intervals, comparing the observed number of breast cancer events to those expected based on incidence rates from Iowa SEER data. Analyses account for the effects of age and calendar period
NP non-proliferative disease, PDWA proliferative disease without atypia, AH atypical hyperplasia, N number of individuals, Obs observed number of breast cancer events, Exp expected number of breast cancer events, SIR standardized incidence ratio, CI confidence interval
a P-value, test of heterogeneity in SIRs across columns