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

	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

^#unknown represents either missing values or values we were not able to classify.

* 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.

^‡the treatment variable indicates that treatment was given.

**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.

Ax = axillary dissection; BCT = breast-conserving surgery; SN = sentinel-node dissection.