Sociodemographic, clinical and cancer characteristics of patients whose breast cancer was detected by screening or by symptoms
| Characteristic | No. (%) of patients | OR (95% CI)* | p value* | |||
|---|---|---|---|---|---|---|
| OBSP-screened n = 13 615 | Non-OBSP-screened n = 9738 | Symptomatic n = 28 107 | OBSP-screened v. symptomatic | Non-OBSP-screened v. symptomatic | ||
| O-BAS | < 0.0001 | |||||
| Yes | 12138 (89.2) | 8261 (84.8) | 22199 (79.0) | 1.74 (1.62 to 1.86) | 1.32 (1.23 to 1.41) | |
| No | 1477 (10.8) | 1477 (15.2) | 5908 (21.0) | Ref. | Ref. | |
| Sociodemographic | ||||||
| Sex | < 0.0001 | |||||
| Female | 13615 (100.0) | 9714 (99.8) | 27706 (98.6) | NA | 0.18 (0.12 to 0.28) | |
| Male | 0 (0.0) | 24 (0.3) | 401 (1.4) | NA | Ref. | |
| Age, yr, mean ± SD (OR per 10-yr increment) | 63.7 ± 8.0 | 62.1 ± 12.2 | 63.4 ± 16.1 | 1.09 (0.07 to 1.11) | 0.96 (0.94 to 0.98) | < 0.0001 |
| Neighbourhood income quintile† | < 0.0001 | |||||
| Highest | 3042 (22.6) | 2243 (23.3) | 5839 (21.0) | Ref. | Ref. | |
| Mid-high | 2727 (20.3) | 1943 (20.2) | 5205 (18.7) | 1.03 (0.96 to 1.11) | 0.99 (0.92 to 1.06) | |
| Middle | 2707 (20.1) | 1870 (19.4) | 5392 (19.4) | 1.02 (0.95 to 1.10) | 0.95 (0.88 to 1.03) | |
| Mid to low | 2703 (20.1) | 1913 (19.9) | 5720 (20.5) | 0.97 (0.90 to 1.04) | 0.94 (0.87 to 1.02) | |
| Lowest | 2275 (16.9) | 1667 (17.3) | 5686 (20.4) | 0.84 (0.78 to 0.91) | 0.85 (0.78 to 0.92) | |
| Neighbourhood immigrant density† | 0.07 | |||||
| Least dense | 8368 (61.9) | 5068 (52.4) | 16322 (58.6) | Ref. | Ref. | |
| Mid-dense | 3124 (23.1) | 2704 (28.0) | 6901 (24.8) | 0.95 (0.89 to 1.01) | 1.04 (0.98 to 1.11) | |
| Most dense | 2018 (14.9) | 1897 (19.6) | 4643 (16.7) | 1.01 (0.93 to 1.10) | 1.09 (1.00 to 1.19) | |
| Rurality† | 0.01 | |||||
| Urban | 11765 (87.4) | 8790 (91.2) | 24713 (88.7) | Ref. | Ref. | |
| Rural | 1693 (12.6) | 848 (8.8) | 3136 (11.3) | 1.14 (1.05 to 1.24) | 1,04 (0.94 to 1.15) | |
| Distance to closest O-BAS, km, mean ± SD (OR per 100-km increment)‡ | 13.2 ± 20.2 | 10.8 ± 14.9 | 12.8 ± 20.8 | 0.96 (0.83 to 1.11) | 0.87 (0.72 to 1.05) | 0.32 |
| Clinical | ||||||
| Charlson Comorbidity Index | < 0.0001 | |||||
| Missing | 5328 (39.1) | 3839 (39.4) | 10072 (35.8) | 1.08 (1.03 to 1.13) | 1.04 (0.99 to 1.10) | |
| 0 | 6738 (49.5) | 4784 (49.1) | 13 621 (48.5) | Ref. | Ref. | |
| 1 | 1095 (8.0) | 778 (8.0) | 2727 (9.7) | 0.83 (0.76 to 0.91) | 0.91 (0.83 to 0.99) | |
| 2 | 277 (2.0) | 185 (1.9) | 942 (3.4) | 0.65 (0.56 to 0.76) | 0.65 (0.55 to 0.76) | |
| ≥ 3 | 177 (1.3) | 152 (1.6) | 745 (2.7) | 0.52 (0.43 to 0.63) | 0.71 (0.59 to 0.86) | |
| Previous breast cancer relative to diagnosis, yr | < 0.0001 | |||||
| Never | 13576 (99.7) | 8693 (89.3) | 25346 (90.2) | Ref. | Ref. | |
| ≤ 5 | < 6 | 83 (0.9) | 235 (0.8) | 0.03 (0.01 to 0.08) | 0.90 (0.69 to 1.18) | |
| 5–10 | 17 (0.1) | 293 (3.0) | 785 (2.8) | 0.03 (0.02 to 0.05) | 1.01 (0.87 to 1.17) | |
| ≥ 10 | 22 (0.2) | 669 (6.9) | 1741 (6.2) | 0.02 (0.01 to 0.03) | 1.05 (0.95 to 1.16) | |
| Previous other cancer relative to diagnosis, yr | < 0.0001 | |||||
| Never | 12718 (93.4) | 9096 (93.4) | 25929 (92.3) | Ref. | Ref. | |
| ≤ 5 | 313 (2.3) | 269 (2.8) | 885 (3.1) | 0.63 (0.54 to 0.72) | 0.96 (0.83 to 1.11) | |
| 5–10 | 221 (1.6) | 149 (1.5) | 452 (1.6) | 0.87 (0.73 to 1.04) | 1.03 (0.85 to 1.25) | |
| ≥ 10 | 363 (2.7) | 224 (2.3) | 841 (3.0) | 0.71 (0.63 to 0.82) | 0.81 (0.69 to 0.95) | |
| Cancer | ||||||
| Laterality | 0.007 | |||||
| Right | 6660 (48.9) | 4735 (48.8) | 13594 (48.7) | Ref. | Ref. | |
| Left | 6881 (50.6) | 4909 (50.6) | 14055 (50.4) | 0.99 (0.95 to 1.04) | 1.00 (0.95 to 1.05) | |
| Bilateral | 71 (0.5) | 61 (0.6) | 252 (0.9) | 0.59 (0.43 to 0.79) | 0.75 (0.56 to 1.01) | |
| Cancer stage | < 0.0001 | |||||
| 0 | 32 (0.2) | 62 (0.6) | 105 (0.4) | 0.52 (0.34 to 0.79) | 0.89 (0.64 to 1.25) | |
| 1 | 8523 (63.5) | 4529 (47.4) | 8166 (29.6) | Ref. | Ref. | |
| 2 | 3859 (28.7) | 3235 (33.8) | 11474 (41.6) | 0.31 (0.29 to 0.32) | 0.50 (0.47 to 0.53) | |
| 3 | 731 (5.4) | 1057 (11.1) | 4369 (15.8) | 0.16 (0.14 to 0.17) | 0.42 (0.39 to 0.46) | |
| 4 | 97 (0.7) | 269 (2.8) | 2062 (7.5) | 0.06 (0.05 to 0.07) | 0.25 (0.22 to 0.29) | |
| Unknown | 185 (1.4) | 405 (4.2) | 1409 (5.1) | 0.27 (0.22 to 0.32) | 0.55 (0.48 to 0.64) | |
| Histology | < 0.0001 | |||||
| Ductal | 10837 (79.6) | 7124 (73.2) | 20954 (74.6) | Ref. | Ref. | |
| Lobular | 1213 (8.9) | 926 (9.5) | 2350 (8.4) | 1.16 (1.07 to 1.26) | 1.28 (1.18 to 1.40) | |
| Ductal and lobular | 604 (4.4) | 441 (4.5) | 1147 (4.1) | 1.06 (0.95 to 1.19) | 1.16 (1.03 to 1.30) | |
| Adenocarcinoma | 292 (2.1) | 264 (2.7) | 740 (2.6) | 1.01 (0.86 to 1.18) | 1.22 (1.04 to 1.43) | |
| Mucinous | 224 (1.6) | 188 (1.9) | 542 (1.9) | 0.56 (0.47 to 0.66) | 0.90 (0.76 to 1.08) | |
| Other | 445 (3.3) | 795 (8.2) | 2374 (8.4) | 0.59 (0.53 to 0.67) | 1.18 (1.07 to 1.30) | |
| Hormone receptor profile | < 0.0001 | |||||
| ER−, PR−, HER2− | 895 (6.6) | 822 (8.4) | 2776 (9.9) | Ref. | Ref. | |
| ER−, PR−, HER2+ | 402 (3.0) | 394 (4.0) | 1336 (4.8) | 0.98 (0.85 to 1.13) | 1.02 (0.88 to 1.17) | |
| ER−, PR+, HER2− | 29 (0.2) | 45 (0.5) | 144 (0.5) | 0.63 (0.41 to 0.98) | 1.08 (0.76 to 1.54) | |
| ER−, PR+, HER2+ | 11 (0.1) | 15 (0.2) | 63 (0.2) | 0.78 (0.40 to 1.53) | 0.98 (0.55 to 1.75) | |
| ER+, PR−, HER2− | 923 (6.8) | 625 (6.4) | 1764 (6.3) | 1.47 (1.30 to 1.66) | 1.14 (1.01 to 1.29) | |
| ER+, PR−, HER2+ | 274 (2.0) | 222 (2.3) | 744 (2.6) | 1.16 (0.98 to 1.37) | 1.03 (0.86 to 1.22) | |
| ER+, PR+, HER2− | 8736 (64.2) | 5347 (54.9) | 14412 (51.3) | 1.45 (1.33 to 1.59) | 1.11 (1.02 to 1.21) | |
| ER+, PR+, HER+ | 742 (5.4) | 575 (5.9) | 1929 (6.9) | 1.15 (1.02 to 1.30) | 1.00 (0.88 to 1.14) | |
| Missing | 1603 (11.8) | 1693 (17.4) | 4939 (17.6) | 1.18 (1.05 to 1.31) | 1.16 (1.04 to 1.29) | |
| Topography | < 0.0001 | |||||
| Upper–outer quadrant | 5462 (40.1) | 3497 (35.9) | 9467 (33.7) | Ref. | Ref. | |
| Overlapping lesion | 2578 (18.9) | 1742 (17.9) | 5018 (17.9) | 0.92 (0.86 to 0.98) | 0.97 (0.91 to 1.04) | |
| Breast NOS | 811 (6.0) | 876 (9.0) | 3176 (11.3) | 0.63 (0.57 to 0.69) | 0.85 (0.77 to 0.93) | |
| Lower–outer quadrant | 1227 (9.0) | 948 (9.7) | 2602 (9.3) | 0.82 (0.75 to 0.89) | 0.99 (0.90 to 1.08) | |
| Upper–inner quadrant | 1986 (14.6) | 1260 (12.9) | 3567 (12.7) | 0.85 (0.79 to 0.91) | 0.91 (0.84 to 0.98) | |
| Lower–inner quadrant | 820 (6.0) | 578 (5.9) | 1630 (5.8) | 0.84 (0.76 to 0.93) | 0.93 (0.84 to 1.04) | |
| Central portion | 477 (3.5) | 539 (5.5) | 1692 (6.0) | 0.63 (0.56 to 0.71) | 1.00 (0.90 to 1.12) | |
| Nipple | 202 (1.5) | 233 (2.4) | 723 (2.6) | 0.58 (0.49 to 0.69) | 0.88 (0.75 to 1.04) | |
| Axillary tail | 52 (0.4) | 65 (0.7) | 232 (0.8) | 0.55 (0.39 to 0.76) | 0.87 (0.65 to 1.16) | |
| Other | ||||||
| Year of diagnosis (row percentages provided) | < 0.0001 | |||||
| 2013 | 2248 (16.5) | 1877 (19.3) | 5679 (20.2) | Ref. | Ref. | |
| 2014 | 2625 (19.3) | 2007 (20.6) | 5563 (19.8) | 1.18 (1.10 to 1.27) | 1.09 (1.01 to 1.18) | |
| 2015 | 2756 (20.2) | 1908 (19.6) | 5569 (19.8) | 1.25 (1.16 to 1.35) | 1.03 (0.96 to 1.12) | |
| 2016 | 2915 (21.4) | 1983 (20.4) | 5679 (20.2) | 1.31 (1.22 to 1.41) | 1.06 (0.98 to 1.15) | |
| 2017 | 3071 (22.6) | 1963 (20.2) | 5617 (20.0) | 1.42 (1.32 to 1.53) | 1.06 (0.98 to 1.15) | |
Note: CI = confidence interval, ER = estrogen receptor, HER2 = human epidermal growth factor receptor 2, NA = not applicable, NOS = not otherwise specified, O-BAS = OBSP-affiliated breast assessment site, OBSP = Ontario Breast Screening Program, OR = odds ratio, PR = progesterone receptor, Ref. = reference category.
↵* n = 49 420; findings derived from a multinomial logistic regression adjusted for all variables in the table and Local Health Information Network. The p value is from a single multinomial multivariable model, representing the overall difference between the 3 groups (symptomatic v. OBSP-screened v. non-OBSP-screened), with the symptomatic group as the reference.
↵† Adapted from Statistics Canada Postal Code Conversion File and Postal Code Conversion File Plus (June 2017), which is based on data licensed from Canada Post Corporation.16 We used the patient’s postal code at diagnosis.
↵‡ Odds ratios reflect the odds of diagnosis in an O-BAS for every 100-km increase in Euclidean distance to the patient’s closest O-BAS. We used the patient’s postal code at diagnosis.