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Table 1 Baseline characteristics of women with incident breast cancer in Norway 1985 to 2004, diagnosed before (pre-program) and after (post-program) introduction of population-based mammography screening program in their county of residence

From: Improved breast cancer survival following introduction of an organized mammography screening program among both screened and unscreened women: a population-based cohort study

  Pre-program
n = 26,883
Post-program
n = 7990
Characteristic Number (%) Number (%)
Age (years 0)     
<40 1492 5.6 658 8.2
40 to 49 4533 16.9 2119 26.5
50 to 69 10,339 38.5 1383 17.3
≥ 70 10.519 39.1 3830 47.9
Stage*     
I 13,035 48.5 3977 50.0
II 10,338 38.5 3201 40.1
III 1414 5.3 348 4.4
IV 1750 6.5 444 5.6
unknown# 346 1.3 20 0.3
Pathologic size     
1 (0 to 20 mm) 7782 28.9 3162 39.6
2 (>20 to 50 mm) 5657 21.0 2270 28.4
3 (>50 mm) 621 2.3 190 2.4
4 (growth) 1429 5.3 443 5.5
unknown# 11,394 42.4 1925 24.1
Treatment     
Radiation therapy 5323 19.8 2942 36.8
unknown# 5113 19.0 1847 23.1
Hormone therapy 8230 30.6 3128 39.2
unknown# 4810 17.9 2041 25.5
Chemotherapy 6792 25.3 2044 25.6
unknown# 5523 20.5 2678 33.5
Surgery 24,694 91.9 6997 87.6
BCT 2160 8.0 2045 25.6
Mastectomy 20,661 76.9 4885 61.1
SN** 572 4.2 1859 23.3
Ax** 10,356 75.6 4486 56.2
  1. #unknown represents either missing values or values we were not able to classify.
  2. * staging is based on the classification of tumor-stage in the Cancer Registry of Norway: I = localized cancer, II = regional cancer (represents no of node 0 positive tumors), III = cancer fixed to either skin or to the chest wall, IV = cancers with distant metastases.
  3. the treatment variable indicates that treatment was given.
  4. **surgical procedures in the axilla were not specified until 1993 in the database; percentage is calculated based on breast cancer patients diagnosed from 1993 to 2004.
  5. Ax = axillary dissection; BCT = breast-conserving surgery; SN = sentinel-node dissection.