Assessing the usefulness of a novel MRI-based breast density estimation algorithm in a cohort of women at high genetic risk of breast cancer: the UK MARIBS study

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

ISSN: 1465-542X