Table 3 Summary of the desirable and undesirable effects from RCTs and observational studies for different screening intervals and age groups.*

From: Benefits and harms of annual, biennial, or triennial breast cancer mammography screening for women at average risk of breast cancer: a systematic review for the European Commission Initiative on Breast Cancer (ECIBC)

Age group

Annual vs. Biennial

Triennial vs. Biennial

Annual vs. Triennial

Certainty of evidence

N° of studies, countries

Relative effect (95%CI)

Absolute reduction (95%CI)

N° of studies, countries

Relative effect (95%CI)

Absolute reduction (95%CI)

N° of studies, countries

Relative effect (95%CI)

Absolute reduction (95%CI)

 

Breast cancer (BC) mortality

40–49

–

–

–

–

–

–

1 (Finland) [39]

RR 1.14 (0.59 to 2.19)**

3 more (7 fewer to 21 more)

Very low

50–69

1 (Canada) [31]

IRR: 0.94 (0.68 to 1.31)

4 fewer (22 fewer to 21 more)

–

–

–

1 (UK) [18]***

RR 0.93 (0.76 to 1.12)

42 fewer (144 fewer to 72 more)

Very low for annual vs biennial and moderate vs triennial

BC stage (IIB–IV)

40–49

1 (US) [37]

OR 0.85 (0.75 to 0.96)

NE

1 (US) [38]

OR 0.78 (0.54 to 1.11)

NE

–

–

–

Very low for all comparisons

50–69

1 (US) [37]

OR: 0.93 (0.81 to 1.09)

NE

1 (US) [38]

OR: 0.83 (0.65 to 1.07)

NE

–

–

–

Very low for all comparisons

70–74

1 (US) [37]

OR 0.98 (0.76 to 1.27)

NE

–

–

–

–

–

–

Very low

Interval cancer

40–49

1 (US) [35]

RR 0.46 (0.16 to 1.36)

81 fewer (126 fewer to 54 more)

–

–

–

–

–

–

Very low

50–69

1 (US) [37]

A: 22% (21% to 30%) of BC cases

B: 27% (26% to 29%) of BC cases

1 (US) [7]

T: 44% (41% to 48%) of BC cases

B: 41% (39% to 42%) of BC cases

1 (US) [7]

A: 30% (29% to 31%) of BC cases

T: 44% (41% to 48%) of BC cases

Very low for all comparisons

70–74

1 (US) [30]

A: 23% (22% to 25%)

B: 33% (30% to 36%)

–

–

–

–

–

–

Very low

False positive results—10 year cumulative probability per woman

40–49

1 (US) [32]

A: 67% (65% to 68%)

B: 45% (44% to 46%)

1 (US) [32]

T: 30% (29% to 30%)

B: 41% (41% to 42%)

1 (US) [38]

A: 65% (63% to 65%)

T: 29% (29% to 30%)

Very low for all comparisons

50–69

1 (US) [32]

A: 54% (53% to 55%)

B: 34% (34% to 35%)

1 (US) [38]

T: 25% (25% to 25%)

B: 35% (35% to 36%)

1 (US) [38]

A: 55% (55% to 56%) T: 25% (25% to 25%)

Very low for all comparisons

70–74

1 (US) [30]

A: 47% (45% to 50%)

B: 27% (26% to 28%)

–

–

–

–

–

–

Very low

False positive biopsy recommendation—10 year cumulative probability per woman

40–49

1 (US) [32]

A: 11% (10% to 13%)

B: 6% (5% to 7%)

1 (US) [32]

T: 4% (4% to 4%)

B: 6% (6% to 6%)

1 (US) [38]

A: 11% (11% to 12%)

T: 4% (4% to 4%)

Very low for all comparisons

50–69

1 (US) [32]

A: 8% (7% to 9%)

B. 5% (4% to 5%)

1 (US) [38]

T: 4% (4% to 4%)

B: 5% (5% to 6%)

1 (US) [38]

A: 10% (9% to 10%)

T: 4% (4% to 4%)

Very low for all comparisons

70–74

1 (US) [30]

A: 9% (8% to 11%)

B: 4% (4% to 5%)

–

–

–

–

–

–

Very low

  1. To review the reference for each study and the reasons for downgrading the certainty of the evidence see Supplementary file Table S4–S12.
  2. *Only the study with the longest time of observation was included when there were several publications with overlapping time periods. When studies provided results stratified by women´s characteristics, we extracted data from subgroups more similar to European context (i.e. white women instead of other ethnic groups).
  3. **We calculated the confidence interval from the raw data reported in the publication as the original interval was not consistent with the main effect and lower interval bound.
  4. ***Randomized clinical trial study.
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