Breast cancer screening

Women of 50-69 years of age are invited by personal letter to take part in breast cancer screening, or mammography, every two years.

More than 80% of the women invited to attend are screened. Fewer than 3 % of participants are invited for further testing, i.e. ultrasound examination and biopsy, and of these cases about 20 % have breast cancer.

A total of about 5 000 women in Finland each year are diagnosed with breast cancer. Of those, over half belong to the screening age-group of 50-69. Some two-thirds of female breast cancers are detected by screening. The remaining breast cancers are found in non-screened individuals or among participants that had been screened but whose cancer did not appear in screening or was only developed after mammography (1.).

The impact of screening on breast cancer mortality has been studied in Finland since the 1990s. Between 1992 and 2003, mortality among women who had been invited to take part in screening was 22 % lower compared to the situation without breast cancer screening (2.). The mortality of  participants who were actually screened was 28 % lower than that would have been expected without screening. The impact of screening on breast cancer mortality was also investigated in the late 2000s and the result has remained unchanged (3.).

International studies have reported that proactive screening reduces breast cancer mortality even over the age range of 70-74 (4.). Extending screening to this age group should be considered.

HARMS OF SCREENING

In addition to its benefits, screening of breast cancer also has harms, such as overdiagnosis. One in five women regularly participating in screening are unnecessarily referred for further tests on at least one occasion (5.).

Screenings also indicate small early stage tumours, some of which will not cause symptoms during a woman’s lifetime. Studies have reported, however, that these constitute only one-tenth, at most, of the breast cancer tumours among women who have participated in screening (6., 7.).

The main indicators of breast cancer screening can be found in screening statistics (in Finnish).

References:

  1. Sarkeala T, Luostarinen T, Dyba T, Anttila A. Breast carcinoma detection modes and death in a female population in relation to population-based mammography screening. SpringerPlus 2014; 3: 348.
  2. Sarkeala, Heinävaara S, Anttila A. Organised mammography screening reduces breast cancer mortality: A cohort study from Finland. Int J Cancer 2008; 122: 164–9.
  3. Heinävaara S, Sarkeala T, Anttila A. Impact of organised mammography screening on breast cancer mortality in a case-control and cohort study. Br J Cancer, doi: 10.1038/bjc.2016.68.
  4. Lauby-Secretan B, Scoccianti C, Loomis D ym. Breast cancer screening – viewpoint of the IARC working group. NEJM 2015; 372: 2353-58.
  5. Hofvind S, Ponti A, Patnick J ym. False-positive results in mammographic screening for breast cancer in Europe: a literature review and survey of service screening programmes. J Med Screen 2012; 19 (Suppl 1): 57–66.
  6. Puliti D, Duffy SW, Miccinesi G ym. Overdiagnosis in mammographic screening for breast cancer in Europe: a literature review. J Med Screen 2012; 19 (Suppl 1): 42–56.
  7. Heinävaara S, Sarkeala T, Anttila A. Overdiagnosis due to breast cancer screening: updated estimates of the Helsinki service study in Finland. Br J Cancer 2014; 111(7): 1463–8.