Table 3.

Regional differences in the breast cancer risk of BRCA1/2 carriers, excluding index cases (adjusted for birth year), in the Netherlands: The study population (Northern Netherlands) compared with the reference population (the rest of the Netherlands)

Regional differences
BRCA1BRCA2 <60BRCA2 ≥60
ModelN (events)HR (95% CI)N (events)HR (95% CI)N (events)HR (95% CI)
Region
 Reference population1,091 (371)1305 (91)129 (3)1
 Study population467 (141)0.66 (0.54–0.81)269 (59)0.64 (0.51–0.81)38 (11)3.99 (1.11–14.35)
Region
 Reference population913 (281)1224 (56)120 (3)1
 Study population467 (141)0.73 (0.59–0.89)269 (59)0.66 (0.46–0.96)38 (11)2.92 (0.81–10.55)
Regiona corrected for OCCR
 Reference population913 (281)1224 (56)120 (3)1
 Study population467 (141)0.75 (0.61–0.93)269 (59)0.50 (0.33–0.77)38 (11)2.61 (0.68–10.00)
  • aIncluding only carriers with known mutation spectrum.