Mammography activity in Norway 1983 to 2008

Figures & data

Table I. Number of mammography examination in Norway 1983 to 2008.

	Norwegian Radiation Protection Authority		Hofvind et al. [12,13]	Norwegian Breast Cancer Screening Program NBCSP
Year	Total number of mammograms	Total number of examined women, excl. NBCSP	Total number of examined women, excl. NBCSP	Total estimated number of examined women
1983	10 000	5 000	NR	0
1988	80 000	40 000	NR	0
1993	221 210	110 605	NR	0
1996	NR	NR	NR	49 505
1997	NR	NR	NR	67 106
1998	NR	NR	NR	66 535
1999	NR	NR	NR	74 940
2000	NR	NR	NR	103 900
2001	NR	NR	NR	128 688
2002	349 057^1	131 758^1	NR	164 025
2003	NR	NR	[86 570]^2	174 516
2004	NR	NR	NR	189 501
2005	NR	NR	100 907	186 052^3
2006	NR	NR	NR	194 603
2007	NR	NR	NR	194 778
2008	340 701	No conversion	99 613	196 073^2

NBCSP, Norwegian Breast Cancer Screening Program.

Notes:

¹349 057 included NBCSP examinations all counted as 1, and non-NBCSP examinations locally counted as 1 or 2. We used an algorithm based on local registration practice to calculated the 131 758 non-NBCSP examinations.

²Private sector only.

³As reported by Hofvind and Sanderud^13.

Figure 1. Number of women examined with mammography in Norway 1983 to 2008.

Table II. Proportion of Norwegian women reporting at least one previous mammography examination in the NOWAC study, and at least one previous mammography examination at first attendance in the organized screening mammography program, NBCSP.

	40–49 years			50–59 years			60–69 years			50–69 years
	N	N, yes	%	N	N, yes	%	N	N, yes	%	%
NOWAC, 1996
– 4 pilot NBCSP counties^1	957	358	37.5%	2167	1064	49.1%	1524	655	43.0%	46.6%
– Non screening counties	1488	514	34.5%	3411	1446	42.4%	2272	830	36.5%	40.0%
– Difference			3.0%			6.7%			6.5%	6.6%
NOWAC, 1997–1998
– 4 pilot NBCSP counties	12 344	3981	32.3%	8536	6275	73.5%	1197	819	68.4%	72.9%
– Non screening counties	19 331	5771	29.9%	14 118	6709	47.5%	1870	764	40.9%	46.7%
– Difference			2.4%			26.0%			27.5%	26.2%
NOWAC, 2002
– 4 pilot NBCSP counties (A)	148	103	69.6%	2841	2730	96.1%	2111	2097	99.3%	97.5%
– New NBCSP counties^2 (B)	194	125	64.4%	3761	3311	88.0%	2688	2323	86.4%	87.4%
– Non screening counties^3 (C)	48	28	58.3%	840	675	80.4%	622	484	77.8%	79.3%
– Difference (A) – (C)			11.3%			15.7%			21.5%	18.2%
NOWAC, 2002
– 4 pilot and new NBCSP counties	342	228	66.7%	6602	6041	91.5%	4799	4420	92.1%	91.8%
SCREENING PROGRAMME 1996–2002
– 4 pilot (A) and new NBCSP counties (B)	NR	NR	NR	202 307	133 871	66.2%	112 558	67 756	60.2%	64.0%
– Difference			NR			25.3%			31.9%	27.8%

Notes:

¹Rogaland; Oslo; Hordaland; Akershus.

²Telemark; Agder; Troms and Finnmark; Østfold; Nordland; Buskerud; Trøndelag; Oppland.

³Møre and Romsdal; Sogn and Fjordane; Hedmark; Vestfold.

Table III. Expected bias in the estimation of the effect of the organized screening mammography program in Norway, NBCSP, on breast cancer mortality.

	Breast cancer death rate per 100 000 before screening	Breast cancer death rate per 100 000 during screening	Relative risk
Expected numbers in the absence of opportunistic screening			0.75
– NBCSP counties	71	((0.22 × 67) + (0.78^1 × 67 × 0.68))^2 = 50
– Non-NBCSP counties	71	67
Expected numbers given the observed opportunistic screening
– NBCSP counties	((0.60 × 71) + (0.40^3 × 71 × 0.68)) = 62	((0.08 × 67) + (0.92^4 × 67 × 0.68)) = 47	0.89
– Non-NBCSP counties	((0.60 × 71) + (0.40^3 × 71 × 0.68)) = 62	((0.36 × 67) + (0.64^5 × 67 × 0.68)) = 53

Note:

¹Participation rate in NBCSP: 78%.

²(((0.22 × 67) + (0.78 × 67 × Y)) / 71) / (67/71) = 0.75, gives Y = 0.68, which is the estimated effect of screening in screened women. This Y is used for the other calculations.

³Proportion of women aged 50–69 with at least one previous mammography examination in NOWAC 1996 data, non-NBCSP counties: 40%.

⁴Proportion of women aged 50–69 with at least one previous mammography examination in NOWAC 2002 data, four pilot and new NBCSP counties: 92%.

⁵Proportion of women reporting at least one prior mammography examination at first NBCSP attendance, 1996–2002: 64%.

Hofvind S, Thoresen S, Langmark F. A pilot study of mammography activity in two private X-ray institutes in Norway. Report No.: 1. Oslo, Norway: Kreftregisteret; 2006. Norwegian.

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Hofvind S, Sanderud A. Use of mammography in Norway in 2005 and 2008. Oslo, Norway: Høgskolan i Oslo; 2010. Norwegian.

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