Table 1 Characteristics of the study population by method of detection
Method of detection | Non-screening-related | Screen-detected | Interval |
|---|---|---|---|
DCIS diagnosis | |||
 Within 12 months after positive first screening, n (%) | NA | 1622 (33.7) | NA |
 Within 12 months after positive subsequent screening, n (%) | NA | 3192 (66.3) | NA |
 Within 30 months of negative screening, n (%) | NA | NA | 577 (88.6) |
 12 to 30 months after positive screening, n (%) | NA | NA | 74 (11.4) |
 ≥30 months after screening participation, n (%) | 159 (10.1) | NA | NA |
 Prior to first screening participation, n (%) | 115 (7.3) | NA | NA |
 In women who never participated in the screening program, n (%) | 1303 (82.6) | NA | NA |
Mammography typea | |||
 Conventional (film) | 159 | 4804 | 651 |
 Digital | 0 | 10 | 0 |
Age at DCIS diagnosis, years | |||
 Median (interquartile range) | 58.1 (51.9–66.8) | 58.7 (53.5–64.3) | 59.8 (55.0–65.7) |
 49–59, n (%) | 868 (55.0) | 2676 (55.6) | 327 (50.2) |
 60–69, n (%) | 450 (28.5) | 1789 (37.2) | 262 (40.3) |
 70–75, n (%) | 259 (16.4) | 349 (7.3) | 62 (9.5) |
Period of DCIS diagnosis | |||
 1989–1998 (implementation phase), n (%) | 1044 (66.2) | 2001 (41.6) | 215 (33.0) |
 1999–2004 (full nationwide coverage), n (%) | 533 (33.8) | 2813 (58.4) | 436 (67.0) |
DCIS grade | |||
 1 | 126 (8.0) | 440 (9.1) | 90 (13.8) |
 2 | 188 (11.9) | 926 (19.2) | 127 (19.5) |
 3 | 288 (18.3) | 1577 (32.8) | 208 (32.0) |
 Unknownb | 975 (61.8) | 1871 (38.9) | 226 (34.7) |
DCIS treatment within 3Â months of diagnosis | |||
 Breast-conserving surgery with radiotherapy, n (%) | 276 (17.5) | 1587 (33.0) | 188 (28.9) |
 Breast-conserving surgery without radiotherapy, n (%) | 443 (28.1) | 1256 (26.1) | 144 (22.1) |
 Mastectomy, n (%) | 858 (54.4) | 1971 (40.9) | 319 (49.0) |
Follow-up interval, years | |||
 Median (interquartile range) | 12.2 (8.1–16.4) | 10.3 (7.7–13.5) | 9.9 (7.3–12.5) |
 0–4c, n (%) | 115 (7.3) | 179 (3.7) | 29 (4.5) |
 5–9, n (%) | 461 (29.2) | 2117 (44.0) | 305 (46.9) |
 ≥10, n (%) | 1001 (63.5) | 2518 (52.3) | 317 (48.7) |
Subsequent invasive breast cancerd | |||
 No, n (%) | 1385 (87.8) | 4357 (90.5) | 592 (90.9) |
 Ipsilateral only, n (%) | 87 (5.5) | 213 (4.4) | 29 (4.5) |
 Contralateral only, n (%) | 94 (6.0) | 225 (4.7) | 25 (3.8) |
 Ipsilateral + contralateral, n (%) | 11 (0.7) | 18 (0.4) | 5 (0.8) |
Vital status at last follow up | |||
 Alive, n (%) | 1153 (73.1) | 4191 (87.1) | 575 (88.3) |
 Dead, n (%) | 398 (25.2) | 594 (12.3) | 68 (10.5) |
 Emigrated, n (%) | 26 (1.7) | 29 (0.6) | 8 (1.2) |
Total | 1577 | 4814 | 651 |