Table 6

Breast cancer risk according to MRI absolute dense volume and Cumulus and visual assessment absolute dense areas (Medial-Lateral Oblique view), by BRCA1/BRCA2 genetic status

No. women

No. cancers

No. pyears

IRR (95% CI) P-value (adjusted age)

IRR (95% CI) P-value (adjusted age, BMI & parity)

BRCA1 Carriers

MRI dense volume

117

21

687

3.62 (1.32, 9.90) 0.012

3.10 (0.95, 10.1) 0.060

Cumulus MLO dense area

94

16

579

1.54 (0.58, 4.10) 0.39

1.27 (0.39, 4.11) 0.69

BRCA2 Carriers

MRI dense volume

69

18

385

3.06 (1.14, 8.19) 0.026

6.75 (1.80, 25.2) 0.005

Cumulus MLO dense area

71

15

418

1.03 (0.34, 3.10) 0.96

1.44 (0.38, 5.47) 0.59

Non-Carriers

MRI dense volume

357

14

2,495

1.27 (0.44, 3.65) 0.66

0.79 (0.24, 2.67) 0.71

Cumulus MLO dense area

332

7

2,367

1.14 (0.25, 5.11) 0.87

0.58 (0.11, 3.06) 0.52

The non-carrier group includes those who tested negative for a known BRCA1/2 family mutation as well as those in whom no mutation was detected after a BRCA1/2 mutation screen, because of the small numbers.

Pyears = number of person-years in study and follow-up period

IRR = incidence rate ratio, estimated for the upper two quartiles vs the lower two quartiles (the trend test was not attempted due to the small numbers)

CI = confidence interval

Thompson et al. Breast Cancer Research 2009 11:R80   doi:10.1186/bcr2447