Adherence to breast cancer guidelines is associated with better survival outcomes: a systematic review and meta-analysis of observational studies in EU countries

Table 2a Characteristics of the included studies (n = 21)

Study characteristics	n (%)	References
Country
France	2 (10%)	[38, 39]
Germany	15 (71%)	[18,19,20,21,22, 30, 37, 41,42,43, 45,46,47,48,49]
Italy	2 (10%)	[17, 40]
Netherlands	2 (10%)	[36, 44]
Publication year
2015–2019	8 (35%)	[17,18,19,20,21,22, 45, 49]
2009–2014	11 (52%)	[30, 40,41,42,43,44] [37, 39, 46,47,48]
≤ 2008	2 (10%)	[36, 38]
Study design
Non-controlled before-after study	3 (14%)	[21, 38, 40]
Retrospective cohort study	18 (86%)	[17,18,19,20, 22, 30, 36, 37, 39, 41,42,43,44,45,46,47,48,49]
Guideline scope
Diagnosis	2 (10%)	[17, 40]
Follow-up	1 (5%)	[38]
Treatment	20 (95%)	[17,18,19,20,21,22, 30, 36, 37, 39,40,41,42,43,44,45,46,47,48,49]
Outcomes‡
Overall survival	18 (86%)	[12,13,14,15,16,17, 24,25,26,27, 29, 31,32,33,34,35,36,37, 49]
Disease free survival	16 (76%)	[13,14,15, 17, 24, 26, 28, 29, 31,32,33,34,35,36,37, 49]
Costs associated to CGs adherence	2 (10%)	[38, 39]
Quality of life	0 (0%)	–
Incidence-based mortality	0 (0%)	–
Harm	0 (0%)	–
Risk of bias
Low	17 (81%)	[17, 20,21,22, 36, 37, 39,40,41,42,43,44, 46,47,48,49]
Moderate	4 (20%)	[18, 19, 38, 45]
High	0 (0%)	–

‡ Percentages exceed 100% because the categories are not mutually exclusive (i.e. some studies involved more than one type of guideline and more than one type of outcome)

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