Table 3.
Hazard ratio with 95% confidence intervals (CI), of breast cancer in ART women (n = 16 629) versus controls (n=792 208)
| ART women | Controls | HR | (95 % CI) | |||
|---|---|---|---|---|---|---|
| n | Person years | n | Person years | |||
| Breast cancer after start of follow up (crude)a | 138 | 141 629 | 7899 | 12 259 492 | 1.35 | (1.14-1.60) |
| Breast cancer after start of follow upb | 138 | 141 629 | 7899 | 12 259 492 | 1.20 | (1.01-1.42) |
| Excluding those with cancer first year | 137 | 141 628 | 7868 | 12 259 476 | 1.20 | (1.01-1.43) |
| Excluding those with any cancer before inclusion | 134 | 140 855 | 7852 | 12 228 308 | 1.17 | (0.98-1.40) |
| Periodb | ||||||
| 1883-1992 | 0 | 3809 | 368 | 1 975 710 | NA | |
| 1993-2002 | 27 | 40 972 | 2304 | 4 801 834 | 1.05 | (0.72-1.55) |
| 2003-2010 | 111 | 96 848 | 5227 | 5 481 949 | 1.23 | (1.01-1.49) |
| Parity at inclusionb | ||||||
| P0 | 96 | 107 056 | 4570 | 8 878 894 | 1.12 | (0.91-1.38) |
| P1 + | 42 | 34 573 | 3329 | 3 380 599 | 1.39 | (1.01-1.90) |
| Parity at end of follow upb,c | ||||||
| 1 | 59 | 59 058 | 1 240 | 1 647 599 | 1.01 | (0.78-1.33) |
| 2 | 62 | 63 102 | 3 549 | 5 362 014 | 1.24 | (0.96-1.60) |
| ≥3 | 17 | 19 468 | 3 110 | 5 249 879 | 1.52 | (0.94-2.46) |
| Age at follow up, yearsb | ||||||
| <40 | 36 | 87 683 | 1 850 | 8 296 713 | 1.17 | (0.84-1.64) |
| 40-50 | 80 | 47 659 | 3 983 | 3 122 918 | 1.12 | (0.89-1.40) |
| =>50 | 22 | 6 286 | 2 066 | 839 862 | 1.20 | (0.78-1.84) |
| Mode of fertility treatmentb | ||||||
| IVF | 111 | 97 368 | 7899 | 12 259 492 | 1.30 | (1.07-1.57) |
| ICSI | 11 | 28 962 | 7899 | 12 259 492 | 0.70 | (0.39-1.27) |
| IVF/ICSI in combination/other/unknown | 16 | 15 299 | 7899 | 12 259 492 | 1.13 | (0.69-1.84) |
| Duration of follow-up, yearsb | ||||||
| < 1 | <5 | 16 582 | 32 | 790 615 | 0.53 | (0.07-4.00) |
| 1 - 5 | 13 | 53 751 | 485 | 2 904 719 | 0.61 | (0.35-1.06) |
| 5 -10 | 50 | 41 079 | 1 197 | 3 046 830 | 1.33 | (0.99-1.78) |
| > 10 | 74 | 30 216 | 6 185 | 5 517 329 | 1.35 | (1.07-1.71) |
a
In the crude estimate, no adjustments for confounding have been made.
b
Adjusted HR: adjusted for attained age, calendar period of follow up, region of residence, parity and age at start of follow up. Each covariate is omitted from the model when it is used for stratification.
c
In multiple gestations, each birth is counted once.