Characteristics of women with early-stage breast cancer treated with surgery in Ontario, 2007 to 2012
| Characteristic | Cohort; no. (%) of patients* | |
|---|---|---|
| Full cohort (n = 26 547) | Collaborative staging cohort (n = 13 291) | |
| Patient-related factors | ||
| Age at diagnosis, yr | ||
| < 40 | 1 036 (3.9) | 499 (3.8) |
| 40–49 | 4 292 (16.2) | 2 090 (15.7) |
| 50–59 | 6 818 (25.7) | 3 359 (25.3) |
| 60–69 | 7 180 (27.0) | 3 548 (26.7) |
| 70–79 | 4 717 (17.8) | 2 420 (18.2) |
| ≥ 80 | 2 504 (9.4) | 1 375 (10.3) |
| Socioeconomic status, by income quintile† | ||
| 1 (lowest) | 4 506 (17.0) | 2 291 (17.3) |
| 2 | 5 158 (19.5) | 2 537 (19.1) |
| 3 | 5 073 (19.2) | 2 546 (19.2) |
| 4 | 5 706 (21.6) | 2 858 (21.6) |
| 5 (highest) | 6 012 (22.7) | 3 019 (22.8) |
| Charlson comorbidity score | ||
| 0 | 19 054 (71.8) | 9 614 (72.3) |
| 1–2 | 2 106 (7.9) | 1 046 (7.9) |
| ≥ 3 | 5 387 (20.3) | 2 631 (19.8) |
| Rurality of residence at diagnosis‡ | ||
| Urban | 24 299 (91.5) | 12 110 (91.1) |
| Rural | 2 248 (8.5) | 1 181 (8.9) |
| Disease-related factors | ||
| Stage | ||
| I | 13 724 (51.7) | 6 836 (51.4) |
| II | 12 823 (48.3) | 6 455 (48.6) |
| Histology | ||
| Ductal | 18 897 (71.2) | 9 375 (70.5) |
| Lobular | 1 638 (6.2) | 866 (6.5) |
| Mixed or other | 6 012 (22.6) | 3 050 (22.9) |
| Tumour grade§ | ||
| 1 | – | 3 095 (23.3) |
| 2 | – | 5 751 (43.3) |
| 3 | – | 3 591 (27.0) |
| Missing | – | 854 (6.4) |
| HER2 status§ | ||
| Positive | – | 1 126 (8.5) |
| Negative | – | 12 165 (91.5) |
| Axillary lymph node involvement§ | ||
| No | – | 10 119 (76.1) |
| Yes | – | 3 172 (23.9) |
| Lymph or vascular invasion§ | ||
| Absent | – | 11 137 (83.8) |
| Present | – | 2 154 (16.2) |
| Triple-negative disease§ | ||
| Absent | – | 11 837 (89.1) |
| Present | – | 1 454 (10.9) |
| Preoperative breast ultrasonography | ||
| No | 1 474 (5.6) | 638 (4.8) |
| Yes | 25 073 (94.4) | 12 653 (95.2) |
| Preoperative breast MRI | ||
| No | 20 431 (77.0) | 9 972 (75.0) |
| Yes | 6 116 (23.0) | 3 319 (25.0) |
| Surgery type | ||
| Breast-conserving | 19 794 (74.6) | 9 828 (73.9) |
| Non–breast-conserving | 6 753 (25.4) | 3 463 (26.1) |
| System-related factors | ||
| Hospital type where surgery performed | ||
| Academic | 8 400 (31.6) | 3 919 (29.5) |
| Community | 18 147 (68.4) | 9 372 (70.5) |
Note: HER2 = human epidermal receptor-2, MRI = magnetic resonance imaging.
↵* Percentages may not sum to 100% because of rounding.
↵† Quintile 1 included patients residing in neighbourhoods with the lowest socioeconomic status. Data for socioeconomic status were missing for 92 patients in the full cohort and for 40 patients in the “collaborative staging” cohort.
↵‡ Based on Rurality Index for Ontario 2008.20
↵§ Covariables that were available for collaborative staging cohort only.