Table 1.
Characteristics of the population-based cohort of patients with ductal carcinoma in situ of the breast*
| Characteristic | All patients | Left-sided DCIS | Right-sided DCIS |
|---|---|---|---|
| No.† (%) | No. (%) | No. (%) | |
| No. of patients | 10444 (100.0) | 5613 (53.9) | 4825 (46.1) |
| Age at DCIS diagnosis, y | |||
| <49 | 2090 (20.0) | 1122 (20.0) | 967 (20.0) |
| 49–59 | 4242 (40.6) | 2258 (40.2) | 1982 (41.1) |
| 60–69 | 3073 (29.4) | 1687 (30.1) | 1385 (28.7) |
| 70–74 | 1039 (9.9) | 546 (9.7) | 491 (10.2) |
| Attained age at end of follow-up, y | |||
| <50 | 586 (5.6) | 309 (5.5) | 277 (5.7) |
| 50–59 | 1923 (18.4) | 998 (17.8) | 924 (19.2) |
| 60–69 | 3567 (34.2) | 1919 (34.2) | 1648 (34.2) |
| 70–79 | 3180 (30.4) | 1758 (31.3) | 1419 (29.4) |
| ≥80 | 1188 (11.4) | 629 (11.2) | 557 (11.5) |
| Treatment period DCIS | |||
| 1989–1992 | 1382 (13.2) | 757 (13.5) | 625 (13.0) |
| 1993–1996 | 2373 (22.7) | 1268 (22.6) | 1102 (22.8) |
| 1997–2000 | 3096 (29.6) | 1702 (30.3) | 1394 (28.9) |
| 2001–2004 | 3590 (34.4) | 1886 (33.6) | 1704 (35.3) |
| Follow-up time, median, y | 10 | 10 | 10 |
| Patients treated with radiotherapy, median, y | 8 | 8 | 8 |
| Follow-up interval, y | |||
| 0 | 7 (0.1) | 3 (0.1) | 4 (0.1) |
| <5 | 481 (4.6) | 251 (4.5) | 230 (4.8) |
| 5–9 | 4653 (44.6) | 2487 (44.3) | 2165 (44.9) |
| 10–14 | 3366 (32.2) | 1834 (32.7) | 1528 (31.7) |
| ≥15 | 1937 (18.5) | 1038 (18.5) | 898 (18.6) |
| Primary DCIS treatment | |||
| Surgery only | 7466 (71.5) | 3985 (71.0) | 3476 (72.0) |
| Mastectomy | 4434 (42.5) | 2318 (41.3) | 2113 (43.8) |
| Lumpectomy | 2014 (19.3) | 1113 (19.8) | 900 (18.7) |
| Type of surgery unknown‡ | 1018 (9.7) | 554 (9.9) | 463 (9.6) |
| Surgery and radiotherapy | 2899 (27.8) | 1584 (28.2) | 1314 (27.2) |
| Mastectomy and radiotherapy | 111 (1.1) | 63 (1.1) | 48 (1.0) |
| Lumpectomy and radiotherapy | 2543 (24.3) | 1393 (24.8) | 1149 (23.8) |
| Type of surgery unknown‡ and radiotherapy | 236 (2.3) | 126 (2.2) | 110 (2.3) |
| Untreated§ | 79 (0.8) | 44 (0.8) | 35 (0.7) |
| Vital status | |||
| Alive | 8916 (85.4) | 4775 (85.1) | 4135 (85.7) |
| Dead | 1319 (12.6) | 724 (12.9) | 595 (12.3) |
| Emigrated | 209 (2.0) | 114 (2.0) | 95 (2.0) |
| Patients ever uniquely identifiable during follow-up|| | 9470 (90.7) | 5081 (90.5) | 4389 (91.0) |
| Laterality | |||
| Left | 5613 (53.7) | ||
| Right | 4825 (46.2) | ||
| Unknown | 6 (0.1) | ||
| Differentiation DCIS | |||
| Well-differentiated | 968 (9.3) | 537 (9.6) | 430 (8.9) |
| Moderately differentiated | 1715 (16.4) | 909 (16.2) | 805 (16.7) |
| Poorly differentiated | 2788 (26.7) | 1462 (26.0) | 1326 (27.5) |
| Unknown¶ | 4973 (47.6) | 2705 (48.2) | 2264 (46.9) |
| History of cardiovascular disease# | 182 (1.7) | 97 (1.7) | 84 (1.7) |
| DCIS diagnosis 1989–1992** | NA | NA | NA |
| DCIS diagnosis 1993–1996** | 9 (0.1) | 4 (0.1) | 5 (0.1) |
| DCIS diagnosis 1997–2000 | 58 (0.6) | 33 (0.6) | 25 (0.5) |
| DCIS diagnosis 2001–2004 | 114 (1.1) | 60 (1.1) | 54 (1.1) |
| Second primary neoplasia | 2124 (20.3) | 1188 (21.2) | 936 (19.4) |
* DCIS = ductal carcinoma in situ of the breast; NA = not available.
† The numbers of left-sided and right-sided DCIS do not add up to the total because of six patients with missing laterality.
‡ Type of surgery was not registered in every region during the first years of the registry.
§ Excluded from analyses.
|| Linkage with the Hospital Discharge Registry is only possible for patients who were ever unique based on postal code, date of birth, and sex.
¶ Time dependent, with “unknown” coded more often during older years of diagnoses.
# History of cardiovascular disease defined as a hospital admission for cardiovascular disease or cardiovascular before the DCIS diagnosis.
** Data on cardiovascular disease is available since 1995.