Table 3.
Odds ratio of CBC and unilateral breast cancer in relation to levels of mammographic density
| Density at diagnosis |
CBC-patients vs. unilateral breast cancer patients |
Unilateral breast cancer patients vs. healthy women | ||||
|---|---|---|---|---|---|---|
| Percent density | N | OR | 95% CI | N | OR | 95% CI |
| ≤5% | 24 | 1.28 | 0.52 to 3.13 | 19 | 0.58 | 0.20 to 1.69 |
| >5 to 25% | 174 | 1.00 | Ref. | 125 | 1.00 | Ref. |
| >25 to 50% | 184 | 1.14 | 0.71 to 1.82 | 111 | 2.27 | 1.18 to 4.37 |
| >50% | 40 | 0.46 | 0.17 to 1.21 | 32 | 2.89 | 1.01 to 8.21 |
| P-value for trend* | 0.40 | <0.01 | ||||
| Area density | N | OR | 95% CI | N | OR | 95% CI |
| ≤20 cm2 | 106 | 1.35 | 0.79 to 2.32 | 85 | 0.65 | 0.36 to 1.17 |
| >20 to 40 cm2 | 144 | 1.00 | Ref. | 101 | 1.00 | Ref. |
| >40 to 60 cm2 | 96 | 1.25 | 0.71 to 2.19 | 52 | 1.40 | 0.69 to 2.83 |
| >60 cm2 | 76 | 1.27 | 0.70 to 2.29 | 49 | 1.58 | 0.76 to 3.26 |
| P-value for trend* | 0.96 | 0.02 | ||||
* Trend test is based on ordered categories of percent density and dense area, respectively.
Analysis of the risk of contralateral breast cancer (CBC) is adjusted by CBC-patients being matched to unilateral breast cancer patients by age at diagnosis, calendar period of diagnosis, follow-up time and adjuvant therapy. The analysis of risk of unilateral breast cancer is adjusted by unilateral breast cancer patients being matched to healthy women by age at mammogram and calendar period of mammogram In addition to matching all models are also adjusted for non-dense area at baseline mammogram. The mammographic density was measured at the time of the first breast cancer for CBC-cases and unilateral controls, mammographic density of the healthy controls were measured in the same calendar period and at the same age as the corresponding control with unilateral breast cancer.