Sociodemographic, clinical and tumour characteristics of patients with breast cancer who were or were not referred to a Breast Assessment Site affiliated with the Ontario Breast Screening Program
| Characteristic | No. (%) of patients* | O-BAS v. non-O-BAS Bivariate | O-BAS v. non-O-BAS Multivariable† | |||
|---|---|---|---|---|---|---|
| Non-O-BAS n = 8862 | O-BAS n = 42 598 | OR (95% CI) | p value | OR (95% CI) | p value | |
| Screening status | < 0.0001 | < 0.0001 | ||||
| Symptomatic | 5908 (66.7) | 22 199 (52.1) | Ref. | Ref. | ||
| Non-OBSP-screened | 1477 (16.7) | 8261 (19.4) | 1.49 (1.40 to 1.58) | 1.32 (1.23 to 1.41) | ||
| OBSP-screened | 1477 (16.7) | 12 138 (28.5) | 2.19 (2.06 to 2.33) | 1.68 (1.57 to 1.80) | ||
| Sociodemographic | ||||||
| Sex | ||||||
| Female | 8750 (98.7) | 42 285 (99.3) | Ref. | Ref. | ||
| Male | 112 (1.3) | 313 (0.7) | 0.58 (0.47 to 0.72) | 0.93 (0.73 to 1.19) | ||
| Age, yr, mean ± SD (OR per 10-yr increment) | 66 ± 14.6 | 63 ± 13.5 | 0.87 (0.85 to 0.88) | 0.88 (0.86 to 0.90) | ||
| Age, yr | < 0.0001 | < 0.0001 | ||||
| < 50 | 1328 (15.0) | 7244 (17.0) | Ref. | |||
| 50–74 | 4833 (54.5) | 26 048 (61.1) | 0.99 (0.93 to 1.06) | |||
| > 74 | 2701 (30.5) | 9306 (21.8) | 0.63 (0.59 to 0.68) | |||
| After-tax neighbourhood income quintile‡ | < 0.0001 | < 0.0001 | ||||
| Highest | 1756 (19.9) | 9368 (22.2) | Ref. | Ref. | ||
| Mid-high | 1640 (18.6) | 8235 (19.5) | 0.94 (0.88 to 1.01) | 0.91 (0.84 to 0.99) | ||
| Middle | 1678 (19.1) | 8291 (19.7) | 0.93 (0.86 to 1.00) | 0.93 (0.85 to 1.00) | ||
| Mid-low | 1797 (20.4) | 8539 (20.3) | 0.89 (0.83 to 0.96) | 0.88 (0.81 to 0.95) | ||
| Lowest | 1933 (22.0) | 7695 (18.3) | 0.75 (0.70 to 0.80) | 0.77 (0.70 to 0.83) | ||
| Neighbourhood immigrant density‡ | 0.004 | 0.0002 | ||||
| Least dense | 5221 (59.4) | 24 537 (58.1) | Ref. | Ref. | ||
| Mid-dense | 2068 (23.5) | 10 661 (25.2) | 1.10 (1.04 to 1.16) | 1.09 (1.01 to 1.17) | ||
| Most dense | 1497 (17.0) | 7061 (16.7) | 1.00 (0.94 to 1.07) | 0.91 (0.83 to 1.00) | ||
| Rurality‡ | ||||||
| Urban | 7479 (84.9) | 37 789 (89.7) | Ref. | Ref. | ||
| Rural | 1326 (15.1) | 4351 (10.3) | 0.65 (0.61 to 0.69) | 0.65 (0.59 to 0.71) | ||
| Distance to closest O-BAS, km, mean ± SD (OR per 100-km increment)§ | 15.7 ± 21.6 | 11.9 ± 19.2 | 0.44 (0.40 to 0.49) | 0.36 (0.31 to 0.42) | ||
| Clinical | ||||||
| Charlson Comorbidity Index | < 0.0001 | 0.0002 | ||||
| Missing | 3011 (34.0) | 16 228 (38.1) | 1.12 (1.06 to 1.18) | 1.04 (0.98 to 1.10) | ||
| 0 | 4318 (48.7) | 20 825 (48.9) | Ref. | Ref. | ||
| 1 | 935 (10.6) | 3665 (8.6) | 0.81 (0.75 to 0.88) | 0.89 (0.82 to 0.97) | ||
| 2 | 316 (3.6) | 1088 (2.6) | 0.71 (0.63 to 0.81) | 0.88 (0.76 to 1.01) | ||
| ≥ 3 | 282 (3.2) | 792 (1.9) | 0.58 (0.51 to 0.67) | 0.78 (0.66 to 0.91) | ||
| Previous breast cancer relative to diagnosis, yr | < 0.0001 | 0.0005 | ||||
| Never | 8074 (91.1) | 39 541 (92.8) | Ref. | Ref. | ||
| ≤ 5 | 72 (0.8) | 250 (0.6) | 0.71 (0.55 to 0.92) | 1.06 (0.79 to 1.41) | ||
| 5–10 | 239 (2.7) | 852 (2.0) | 0.73 (0.63 to 0.84) | 1.21 (1.03 to 1.43) | ||
| ≥ 10 | 477 (5.4) | 1955 (4.6) | 0.84 (0.76 to 0.93) | 1.25 (1.11 to 1.41) | ||
| Previous other cancer relative to diagnosis, yr | < 0.0001 | 0.15 | ||||
| Never | 8180 (92.3) | 39 563 (92.9) | Ref. | Ref. | ||
| ≤ 5 | 295 (3.3) | 1172 (2.8) | 0.82 (0.72 to 0.94) | 1.01 (0.87 to 1.17) | ||
| 5–10 | 136 (1.5) | 686 (1.6) | 1.04 (0.87 to 1.26) | 1.22 (1.00 to 1.50) | ||
| ≥ 10 | 251 (2.8) | 1177 (2.8) | 0.97 (0.84 to 1.11) | 1.11 (0.95 to 1.29) | ||
| Cancer | ||||||
| Laterality | 0.47 | 0.03 | ||||
| Right | 4288 (48.4) | 20 701 (48.7) | Ref. | Ref. | ||
| Left | 4329 (49.9) | 21 516 (50.6) | 1.03 (0.98 to 1.08) | 1.02 (0.97 to 1.08) | ||
| Bilateral | 65 (0.7) | 319 (0.7) | 1.02 (0.78 to 1.33) | 1.47 (1.09 to 1.98) | ||
| Cancer stage | < 0.0001 | < 0.0001 | ||||
| 0 | 28 (0.3) | 171 (0.4) | 0.91 (0.61 to 1.36) | 1.57 (1.02 to 2.42) | ||
| 1 | 2755 (31.7) | 18 463 (44.1) | Ref. | Ref. | ||
| 2 | 2861 (32.9) | 15 707 (37.5) | 0.82 (0.77 to 0.87) | 0.91 (0.85 to 0.97) | ||
| 3 | 1134 (13.0) | 5023 (12.0) | 0.66 (0.61 to 0.71) | 0.75 (0.69 to 0.82) | ||
| 4 | 1085 (12.5) | 1343 (3.2) | 0.19 (0.17 to 0.20) | 0.23 (0.21 to 0.26) | ||
| Unknown | 832 (9.6) | 1167 (2.8) | 0.21 (0.19 to 0.23) | 0.37 (0.32 to 0.42) | ||
| Histology | < 0.0001 | < 0.0001 | ||||
| Ductal | 6254 (70.6) | 32 661 (76.7) | Ref. | Ref. | ||
| Lobular | 800 (9.0) | 3689 (8.7) | 0.88 (0.81 to 0.96) | 1.00 (0.92 to 1.10) | ||
| Ductal and lobular | 298 (3.4) | 1894 (4.4) | 1.21 (1.07 to 1.38) | 1.20 (1.05 to 1.38) | ||
| Adenocarcinoma | 366 (4.1) | 930 (2.2) | 0.49 (0.43 to 0.55) | 0.73 (0.62 to 0.84) | ||
| Mucinous | 157 (1.8) | 797 (1.9) | 0.97 (0.82 to 1.16) | 1.02 (0.84 to 1.23) | ||
| Other | 987 (11.1) | 2627 (6.2) | 0.51 (0.47 to 0.55) | 0.89 (0.81 to 0.98) | ||
| Hormone receptor profile | 0.08 | < 0.0001 | ||||
| ER−, PR−, HER2− | 679 (7.7) | 3814 (9.0) | Ref. | Ref. | ||
| ER−, PR−, HER2+ | 325 (3.7) | 1807 (4.2) | 0.99 (0.86 to 1.14) | 1.02 (0.88 to 1.20) | ||
| ER−, PR+, HER2− | 36 (0.4) | 182 (0.4) | 0.90 (0.62 to 1.30) | 1.10 (0.75 to 1.64) | ||
| ER−, PR+, HER2+ | 20 (0.2) | 69 (0.2) | 0.61 (0.37 to 1.02) | 0.91 (0.53 to 1.57) | ||
| ER+, PR−, HER2− | 561 (6.3) | 2751 (6.5) | 0.87 (0.77 to 0.99) | 0.87 (0.76 to 0.99) | ||
| ER+, PR−, HER2+ | 204 (2.3) | 1036 (2.4) | 0.90 (0.76 to 1.07) | 0.94 (0.78 to 1.13) | ||
| ER+, PR+, HER2− | 4379 (49.4) | 24 116 (56.6) | 0.98 (0.90 to 1.07) | 0.90 (0.82 to 0.99) | ||
| ER+, PR+, HER2+ | 473 (5.3) | 2773 (6.5) | 1.04 (0.92 to 1.19) | 0.97 (0.85 to 1.11) | ||
| Missing | 2185 (24.7) | 6050 (14.2) | 0.49 (0.45 to 0.54) | 0.66 (0.59 to 0.74) | ||
| Topography | < 0.0001 | < 0.0001 | ||||
| Upper–outer quadrant | 2754 (31.1) | 15 672 (36.8) | Ref. | Ref. | ||
| Breast NOS | 1452 (16.4) | 3411 (8.0) | 0.41 (0.38 to 0.44) | 0.70 (0.64 to 0.76) | ||
| Overlapping lesion | 1618 (18.3) | 7720 (18.1) | 0.84 (0.78 to 0.90) | 0.93 (0.87 to 1.00) | ||
| Upper–inner quadrant | 1007 (11.4) | 5806 (13.6) | 1.01 (0.94 to 1.10) | 0.98 (0.90 to 1.07) | ||
| Lower–outer quadrant | 721 (8.1) | 4056 (9.5) | 0.99 (0.90 to 1.08) | 1.00 (0.91 to 1.10) | ||
| Central portion | 503 (5.7) | 2205 (5.2) | 0.77 (0.69 to 0.86) | 0.91 (0.81 to 1.02) | ||
| Lower–inner quadrant | 470 (5.3) | 2558 (6.0) | 0.96 (0.86 to 1.06) | 0.98 (0.87 to 1.10) | ||
| Nipple | 236 (2.7) | 922 (2.2) | 0.69 (0.59 to 0.80) | 0.77 (0.66 to 0.91) | ||
| Axillary tail | 101 (1.1) | 248 (0.6) | 0.43 (0.34 to 0.55) | 0.56 (0.43 to 0.72) | ||
| Other | ||||||
| Year of diagnosis (row percentages provided) | 0.01 | 0.04 | ||||
| 2013 | 1767 (19.9) | 8037 (18.9) | Ref. | Ref. | ||
| 2014 | 1748 (19.7) | 8447 (19.8) | 1.06 (0.99 to 1.14) | 1.03 (0.95 to 1.11) | ||
| 2015 | 1715 (19.4) | 8518 (20.0) | 1.09 (1.02 to 1.18) | 1.03 (0.96 to 1.12) | ||
| 2016 | 1882 (21.2) | 8695 (20.4) | 1.02 (0.95 to 1.09) | 0.98 (0.90 to 1.06) | ||
| 2017 | 1750 (19.7) | 8901 (20.9) | 1.12 (1.04 to 1.20) | 1.10 (1.02 to 1.19) | ||
Note: CI = confidence interval, ER = estrogen receptor, HER2 = human epidermal growth factor receptor 2, 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, SD = standard deviation.
↵* Unless indicated otherwise.
↵† n = 49 420; adjusted for screening status, age, neighbourhood income quintile, neighbourhood immigrant density, rurality, distance to the closest O-BAS, Charlson Comorbidity Index, previous breast cancer, previous other cancer, laterality, cancer stage, hormone receptor profile, topography, year of diagnosis and Local Health Integration Network.
↵‡ 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 ratio reflects 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.