Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Comparative Study
. 2010 Sep 23;363(13):1203-10.
doi: 10.1056/NEJMoa1000727.

Effect of screening mammography on breast-cancer mortality in Norway

Mette Kalager  1 , Marvin Zelen, Frøydis Langmark, Hans-Olov Adami
Affiliations
Free article
Comparative Study

Effect of screening mammography on breast-cancer mortality in Norway

Mette Kalager et al. N Engl J Med. .
Free article

Abstract

Background: A challenge in quantifying the effect of screening mammography on breast-cancer mortality is to provide valid comparison groups. The use of historical control subjects does not take into account chronologic trends associated with advances in breast-cancer awareness and treatment.

Methods: The Norwegian breast-cancer screening program was started in 1996 and expanded geographically during the subsequent 9 years. Women between the ages of 50 and 69 years were offered screening mammography every 2 years. We compared the incidence-based rates of death from breast cancer in four groups: two groups of women who from 1996 through 2005 were living in counties with screening (screening group) or without screening (nonscreening group); and two historical-comparison groups that from 1986 through 1995 mirrored the current groups.

Results: We analyzed data from 40,075 women with breast cancer. The rate of death was reduced by 7.2 deaths per 100,000 person-years in the screening group as compared with the historical screening group (rate ratio, 0.72; 95% confidence interval [CI], 0.63 to 0.81) and by 4.8 deaths per 100,000 person-years in the nonscreening group as compared with the historical nonscreening group (rate ratio, 0.82; 95% CI, 0.71 to 0.93; P<0.001 for both comparisons), for a relative reduction in mortality of 10% in the screening group (P=0.13). Thus, the difference in the reduction in mortality between the current and historical groups that could be attributed to screening alone was 2.4 deaths per 100,000 person-years, or a third of the total reduction of 7.2 deaths.

Conclusions: The availability of screening mammography was associated with a reduction in the rate of death from breast cancer, but the screening itself accounted for only about a third of the total reduction. (Funded by the Cancer Registry of Norway and the Research Council of Norway.)

PubMed Disclaimer

Comment in

  • Screening mammography--a long run for a short slide?
    Welch HG. Welch HG. N Engl J Med. 2010 Sep 23;363(13):1276-8. doi: 10.1056/NEJMe1008369. N Engl J Med. 2010. PMID: 20860510 No abstract available.
  • More on screening mammography.
    Jørgensen KJ, Zahl PH, Gøtzsche PC. Jørgensen KJ, et al. N Engl J Med. 2011 Jan 20;364(3):284; author reply 285-6. doi: 10.1056/NEJMc1011881. N Engl J Med. 2011. PMID: 21247320 No abstract available.
  • More on screening mammography.
    Fletcher SW, Elmore JG. Fletcher SW, et al. N Engl J Med. 2011 Jan 20;364(3):283; author reply 285-6. doi: 10.1056/NEJMc1011881. N Engl J Med. 2011. PMID: 21247321 No abstract available.
  • More on screening mammography.
    Duffy SW, Smith RA. Duffy SW, et al. N Engl J Med. 2011 Jan 20;364(3):283; author reply 285-6. doi: 10.1056/NEJMc1011881. N Engl J Med. 2011. PMID: 21247322 No abstract available.
  • More on screening mammography.
    van Ravesteyn NT, Heijnsdijk EA, de Koning HJ. van Ravesteyn NT, et al. N Engl J Med. 2011 Jan 20;364(3):282-3; author reply 285-6. doi: 10.1056/NEJMc1011881. N Engl J Med. 2011. PMID: 21247323 No abstract available.
  • More on screening mammography.
    Burke JP, Barry M, Kell MR. Burke JP, et al. N Engl J Med. 2011 Jan 20;364(3):281-2; author reply 285-6. doi: 10.1056/NEJMc1011881. N Engl J Med. 2011. PMID: 21247324 No abstract available.

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

Publication types