Table 2.
Risk of contralateral breast cancer among patients with invasive breast cancer.
| Variable | Value | N (%) | 20-Year cumulative incidencea | Events | Person-years | Rate (% per year) | Unadjustedb | Adjustedb | ||
|---|---|---|---|---|---|---|---|---|---|---|
| Hazard ratio | P value | Hazard ratio | P value | |||||||
| Overall | 659,639 | 7.9% (7.8–8.1) | 20,687 | 5,575,378 | 0.37 | |||||
| Age at diagnosis | 30–39 | 36,646 (5.6%) | 8.7% (8.2–9.3) | 1499 | 336,030 | 0.45 | 1.22 (1.15–1.29) | <0.0001 | 1.22 (1.15–1.29) | <0.0001 |
| 40–49 | 134,759 (20.4%) | 7.2% (7.0–7.5) | 4274 | 1,258,853 | 0.34 | 0.97 (0.94–1.01) | 0.1809 | 0.98 (0.94–1.02) | 0.2743 | |
| 50–59 | 180,970 (27.4%) | 8.0% (7.7–8.3) | 5654 | 1,593,934 | 0.35 | 1.00 [reference] | 1.00 [reference] | |||
| 60–69 | 176,464 (26.8%) | 8.4% (8.1–8.7) | 5535 | 1,424,156 | 0.39 | 1.04 (1.00–1.07) | 0.0637 | 1.03 (1.00–1.07) | 0.0719 | |
| 70–79 | 130,800 (19.8%) | 7.5% (7.1–7.9) | 3725 | 962,405 | 0.39 | 0.87 (0.84-0.91) | <0.0001 | 0.87 (0.83–0.91) | <0.0001 | |
| Race | White | 532,891 (80.8%) | 7.7% (7.5–7.9) | 16,653 | 4,596,134 | 0.36 | 1.00 [reference] | 1.00 [reference] | ||
| Black | 66,356 (10.1%) | 10.0% (9.4–10.6) | 2312 | 484,610 | 0.48 | 1.21 (1.16–1.26) | <0.0001 | 1.17 (1.12–1.22) | <0.0001 | |
| Asian | 43,645 (6.6%) | 8.1% (7.5–8.7) | 1312 | 368,953 | 0.36 | 1.03 (0.98–1.09) | 0.2723 | 1.03 (0.97–1.09) | 0.3387 | |
| Other/unknown | 16,747 (2.5%) | 8.0% (6.9–9.3) | 410 | 125,682 | 0.33 | 0.93 (0.84–1.03) | 0.1502 | 0.93 (0.84–1.02) | 0.1318 | |
| Histological type | Ductal | 562,012 (85.2%) | 7.8% (7.6–7.9) | 17,331 | 4,744,110 | 0.37 | 1.00 [reference] | 1.00 [reference] | ||
| Lobular | 52,869 (8.0%) | 8.0% (7.4–8.5) | 1610 | 431,970 | 0.37 | 1.01 (0.96–1.06) | 0.6876 | 1.05 (1.00–1.11) | 0.0633 | |
| Mixed | 44,758 (6.8%) | 9.8% (9.1–10.5) | 1746 | 399,298 | 0.44 | 1.21 (1.15–1.27) | <0.0001 | 1.28 (1.22–1.35) | <0.0001 | |
| Tumour grade | I | 131,917 (20.0%) | 7.6% (7.2–8.0) | 3691 | 1,081,640 | 0.34 | 1.00 [reference] | 1.00 [reference] | ||
| II | 258,994 (39.3%) | 7.6% (7.4–7.9) | 7482 | 2,149,515 | 0.35 | 0.98 (0.94–1.02) | 0.3673 | 0.98 (0.94–1.02) | 0.2904 | |
| III/IV | 218,201 (33.1%) | 8.4% (8.1–8.7) | 7124 | 1,765,775 | 0.4 | 1.06 (1.02–1.10) | 0.0064 | 0.98 (0.93–1.02) | 0.2879 | |
| Unknown | 50,527 (7.7%) | 8.3% (7.9–8.6) | 2390 | 578,448 | 0.41 | 1.15 (1.10–1.22) | <0.0001 | 1.07 (1.02–1.13) | 0.0094 | |
| Tumour size | <1 cm | 129,667 (19.7%) | 7.3% (7.0–7.6) | 3849 | 1,104,483 | 0.35 | 1.03 (0.99–1.07) | 0.1069 | 1.01 (0.97–1.05) | 0.7135 |
| 1–1.9 cm | 250,072 (37.9%) | 7.5% (7.3–7.8) | 7782 | 2,237,453 | 0.35 | 1.00 [reference] | 1.00 [reference] | |||
| 2–2.9 cm | 137,542 (20.9%) | 8.0% (7.7–8.3) | 4254 | 1,158,954 | 0.37 | 0.99 (0.96–1.03) | 0.6759 | 1.00 (0.97–1.04) | 0.8315 | |
| 3–4.9 cm | 86,544 (13.1%) | 9.0% (8.5–9.5) | 2708 | 654,485 | 0.41 | 1.03 (0.99–1.08) | 0.1333 | 1.05 (1.00–1.10) | 0.0407 | |
| 5–9.9 cm | 37,326 (5.7%) | 10.2% (9.3–11.1) | 1253 | 253,757 | 0.49 | 1.13 (1.06–1.20) | <0.0001 | 1.15 (1.08–1.22) | <0.0001 | |
| 10–15 cm | 3942 (0.6%) | 11.0% (8.6–14.0) | 173 | 22,744 | 0.76 | 1.53 (1.31–1.78) | <0.0001 | 1.53 (1.31–1.79) | <0.0001 | |
| Unknown | 14,546 (2.2%) | 9.0% (8.2–9.9) | 668 | 143,503 | 0.47 | 1.31 (1.21–1.41) | <0.0001 | 1.19 (1.10–1.29) | <0.0001 | |
| Nodal status | N0 | 451,814 (68.5%) | 7.8% (7.7–8.0) | 14,497 | 3,938,163 | 0.37 | 1.00 [reference] | 1.00 [reference] | ||
| N1 | 145,237 (22.0%) | 7.8% (7.5–8.2) | 4201 | 1,191,437 | 0.35 | 0.90 (0.86–0.93) | <0.0001 | 0.90 (0.87–0.94) | <0.0001 | |
| N2 | 40,371 (6.1%) | 8.5% (7.9–9.3) | 1240 | 308,128 | 0.4 | 0.88 (0.83–0.94) | <0.0001 | 0.86 (0.81–0.92) | <0.0001 | |
| N3 | 22,217 (3.4%) | 9.1% (8.2–10.2) | 749 | 137,650 | 0.54 | 0.99 (0.92–1.06) | 0.7129 | 0.92 (0.85–0.99) | 0.0368 | |
| ER status | Negative | 121,381 (18.4%) | 9.3% (9.0–9.7) | 4752 | 1,001,043 | 0.47 | 1.00 [reference] | 1.00 [reference] | ||
| Positive | 486,000 (73.7%) | 7.5% (7.3–7.7) | 13,396 | 3,969,068 | 0.34 | 0.77 (0.74–0.79) | <0.0001 | 0.73 (0.69–0.76) | <0.0001 | |
| Unknown | 52,258 (7.9%) | 8.3% (7.9–8.7) | 2539 | 605,267 | 0.42 | 0.92 (0.88–0.97) | 0.0009 | 0.75 (0.68–0.83) | <0.0001 | |
| PR status | Negative | 180,765 (27.4%) | 8.7% (8.4–9.0) | 6120 | 1,461,673 | 0.42 | 1.00 [reference] | 1.00 [reference] | ||
| Positive | 416,884 (63.2%) | 7.5% (7.3–7.7) | 11,564 | 3,399,161 | 0.34 | 0.88 (0.85–0.91) | <0.0001 | 1.06 (1.01–1.10) | 0.0111 | |
| Unknown | 61,990 (9.4%) | 8.4% (8.0–8.7) | 3003 | 714,545 | 0.42 | 1.04 (1.00–1.09) | 0.0557 | 1.20 (1.10–1.31) | <0.0001 | |
| Radiotherapy | No | 276,971 (42.0%) | 7.7% (7.5–7.9) | 8944 | 2,404,755 | 0.37 | 1.00 [reference] | 1.00 [reference] | ||
| Yes | 367,346 (55.7%) | 8.1% (7.9–8.4) | 11,396 | 3,066,768 | 0.37 | 1.05 (1.02–1.08) | 0.0002 | 1.08 (1.05–1.12) | <0.0001 | |
| Unknown | 15,322 (2.3%) | 7.2% (6.2–8.4) | 347 | 103,855 | 0.33 | 0.91 (0.82–1.01) | 0.0766 | 0.91 (0.82–1.01) | 0.084 | |
| Chemotherapy | No/unknown | 383,593 (58.2%) | 7.8% (7.6–8.0) | 12,404 | 3,327,267 | 0.37 | 1.00 [reference] | 1.00 [reference] | ||
| Yes | 276,046 (41.8%) | 8.1% (7.9–8.4) | 8283 | 2,248,112 | 0.37 | 0.97 (0.95–1.00) | 0.0679 | 0.92 (0.89–0.95) | <0.0001 | |
a20-Year cumulative incidence estimated using the non-parametric Kaplan–Meier method.
bAnalysis conducted using the Fine and Gray proportional sub-hazards model to account for competing risks of death. Sub-distribution hazard ratios adjusted for all variables are presented in the table.