Table 2.
SIRs for contralateral breast cancer among 1-year survivors of a first primary breast cancer in 12 SEER registries, 1992–2016
| First breast cancer characteristic | No. of CBCs (%) | SIR (95% CI) |
|---|---|---|
| Overall | 12,986 (100.0) | 2.21 (2.17 to 2.25) |
| Age at diagnosis, years | ||
| < 40 | 1002 (7.7) | 6.41 (6.02 to 6.82) |
| 40 to < 50 | 2691 (20.7) | 2.79 (2.69 to 2.90) |
| 50 to < 60 | 3452 (26.6) | 2.07 (2.00 to 2.14) |
| 60 to < 70 | 3292 (25.4) | 1.91 (1.85 to 1.98) |
| ≥ 70 | 2549 (19.6) | 1.87 (1.80 to 1.94) |
| Time since diagnosis | ||
| < 5 years | 4620 (35.6) | 2.03 (1.97 to 2.09) |
| ≥ 5 years | 8366 (64.4) | 2.32 (2.27 to 2.37) |
| Stage at diagnosis | ||
| I | 6899 (53.1) | 2.08 (2.03 to 2.13) |
| II | 4364 (33.6) | 2.21 (2.14 to 2.28) |
| III | 1723 (13.3) | 2.97 (2.83 to 3.11) |
| Histology | ||
| Ductal | 9340 (71.9) | 2.17 (2.13 to 2.21) |
| Lobular | 1037 (8.0) | 2.06 (1.94 to 2.19) |
| Mixed | 1126 (8.7) | 2.49 (2.35 to 2.64) |
| Other | 1483 (11.4) | 2.44 (2.32 to 2.57) |
| ER status | ||
| Positive | 8372 (64.5) | 1.98 (1.94 to 2.02) |
| Negative | 3024 (23.3) | 3.05 (2.94 to 3.16) |
| Initial treatment | ||
| Radiation therapy | ||
| Yes | 7180 (55.3) | 2.25 (2.20 to 2.30) |
| No/unknown | 5806 (44.7) | 2.17 (2.11 to 2.23) |
| Chemotherapy | ||
| Yes | 5086 (39.2) | 2.49 (2.42 to 2.56) |
| No/unknown | 7900 (60.8) | 2.06 (2.01 to 2.11) |
| Hormone therapy | ||
| Yes | 4442 (34.2) | 1.88 (1.83 to 1.94) |
| No/unknown | 8544 (65.8) | 2.43 (2.38 to 2.48) |
| HER2 statusa | ||
| Positive | 93 (11.8) | 1.45 (1.17 to 1.78) |
| Negative | 646 (82.2) | 1.57 (1.45 to 1.70) |
| Breast cancer subtypea,b | ||
| HR+/HER2+ | 66 (8.4) | 1.47 (1.14 to 1.87) |
| HR+/HER2− | 534 (67.9) | 1.47 (1.35 to 1.60) |
| HR−/HER2+ | 27 (3.4) | 1.42 (0.94 to 2.07) |
| HR−/HER2− (triple negative) | 111 (14.1) | 2.43 (2.00 to 2.93) |
SEER, Surveillance, Epidemiology, and End Results; CBC, contralateral breast cancer; SIRs, standardized incidence ratios; CI, confidence interval; ER, estrogen receptor; HER2, human epidermal growth factor receptor 2; HR, hormone receptor; PR, progesterone receptor
aHER2 status routinely collected in 2010 and onwards. Estimates include first breast cancers diagnosed between 2010 and 2015 and followed through 2016 (no. of first breast cancers = 115,835; no. of contralateral breast cancers = 786; overall SIR = 1.57, 95% CI = 1.46–1.68)
bHR+ = ER+ and/or PR+; HR− = ER− and PR−