Table 1.
Distribution of main covariates according to use of AIT
| Use of AIT | No use of AIT | |||
|---|---|---|---|---|
| n | % | n | % | |
| Overall | 7919 | 100.0% | 2542 | 100.0% |
| Demographic characteristics at index datea | ||||
| Age (median, IQR) | 68(62,75) | 67(62,72) | ||
| Calendar period | ||||
| 2009–2012 | 1374 | 17.4% | 629 | 24.7% |
| 2013–2016 | 2748 | 34.7% | 816 | 32.1% |
| 2017–2020 | 3797 | 47.9% | 1097 | 43.2% |
| Disposable household income | ||||
| 1st quartile | 2344 | 29.6% | 725 | 28.5% |
| 2nd quartile | 2618 | 33.1% | 855 | 33.6% |
| 3rd quartile | 1671 | 21.1% | 563 | 22.1% |
| 4th quartile | 1286 | 16.2% | 399 | 15.7% |
| Educationb | ||||
| < 10 years | 2664 | 33.6% | 887 | 34.9% |
| 10–12 years | 3179 | 40.1% | 1011 | 39.8% |
| 13–15 years | 1749 | 22.1% | 559 | 22.0% |
| ≥ 15 years | 327 | 4.1% | 85 | 3.3% |
| Co-habitation | ||||
| Yes | 4808 | 60.7% | 1556 | 61.2% |
| No | 3111 | 39.3% | 986 | 38.8% |
| Tumor characteristics | ||||
| Lateralityb | ||||
| Left | 4083 | 51.6% | 1306 | 51.4% |
| Right | 3836 | 48.4% | 1236 | 48.6% |
| Tumor sizeb | ||||
| < = 1 cm | 851 | 10.7% | 1119 | 44.0% |
| > 1–2 cm | 4337 | 54.8% | 827 | 32.5% |
| > 2–5 cm | 2500 | 31.6% | 551 | 21.7% |
| > 5 cm | 231 | 2.9% | 45 | 1.8% |
| Histology and gradeb | ||||
| Lobular—Grades I-IIIc | 1179 | 14.9% | 172 | 6.8% |
| Ductal—Grade I | 1530 | 19.3% | 894 | 35.2% |
| Ductal—Grade II | 3663 | 46.3% | 254 | 10.0% |
| Ductal—Grade III | 1065 | 13.4% | 800 | 31.5% |
| Other histology | 482 | 6.1% | 422 | 16.6% |
| Lymph node involvementb | ||||
| Negative | 4907 | 62.0% | 2117 | 83.3% |
| Positived | 3012 | 38.0% | 425 | 16.7% |
| 1–3 positive lymph nodes | 2231 | 28.2% | 239 | 9.4% |
| 4–9 positive lymph nodes | 444 | 5.6% | 76 | 3.0% |
| ≥ 10 positive lymph nodes | 245 | 3.1% | 43 | 1.7% |
| HER2-statusb | ||||
| Positive | 718 | 9.1% | 353 | 13.9% |
| Negative | 7201 | 90.9% | 2189 | 86.1% |
| Treatment characteristics | ||||
| Type of primary surgeryb | ||||
| Mastectomy | 2179 | 27.5% | 556 | 21.9% |
| Breast conserving surgery | 5740 | 72.5% | 1986 | 78.1% |
| Radiotherapy (allocation) | ||||
| Yes | 6673 | 84.3% | 2148 | 84.5% |
| No | 1246 | 15.7% | 394 | 15.5% |
| Chemotherapyb | ||||
| Yes | 1650 | 20.8% | 1218 | 47.9% |
| No | 6269 | 79.2% | 1324 | 52.1% |
| Neoadjuvant treatment | ||||
| Yes | 227 | 2.9% | 188 | 7.4% |
| No | 7692 | 97.1% | 2354 | 92.6% |
AIT, aromatase inhibitor treatment; HER2, human epidermal growth factor receptor 2; IQR, interquartile range.
‘Use of AIT’ is defined as allocated and dispensed treatment with AIT, and ‘No use of AIT’ is defined as no allocated and no dispensed treatment with AIT; both as recorded in the clinical database of the Danish Breast Cancer Group (see Table S3 for further definitions).
aDefined as date of breast cancer diagnosis (defined as surgery date or biopsy date if neoadjuvant treatment) as recorded in the clinical database of the Danish Breast Cancer Group.
bMissing information was imputed as described in Table S3 (education = 142, laterality < 5, tumor size = 44, histology and grade = 83, lymph node involvement = 55, HER2-status = 121, type of primary surgery = 28, chemotherapy = 287).
cLobular grade I, II and III have been grouped due to small numbers. When adjusting, lobular tumors are grouped according to grade I, II and III.
dNumbers of women within the categories of number of positive lymph nodes do not summarize to 3012 since for some of the women number of positive lymph nodes were unknown (primarily patients who had received neoadjuvant treatment).