Table 1.

Characteristics of the studies selected for the systematic review

Characteristics	Model development studies	Internal validation studies	External validation studies
Number of studies	54 studies	42 studies	49 studies
Number of models	58 models	42 models	17 models
Year of publication	1982–2016	1982–2016	1987–2016
Study design
Prospective	2 studies	2 studies	0 study
Retrospective	32 studies	23 studies	30 studies
Unknown	20 studies	18 studies	19 studies
Source of data
Population-based	14 studies	11 studies	12 studies
Hospital-based	31 studies	29 studies	33 studies
RCT-based	6 studies	1 study	4 studies
Unknown	3 studies	2 studies	0 study
Sample size	75–433,272	30–433,272	48–387,262
Number of events
Deaths	27–24,610	27–24,610	11–3902
Recurrences	5–1030	5–950	9–1188
Country of participants
Europe	24 studies	22 studies	29 studies
North America	13 studies	8 studies	7 studies
Asia	11 studies	10 studies	11 studies
Others	2 studies (Australia)	0 study	3 studies (1 Australia. 1 New Zealand, 1 Brazil)
Strengths concluded by the authors of the selected studies
Adhere to good practice	1 study	1 study	0 study
Large sample size	2 studies	2 studies	4 studies
Patients diagnosed recently	1 study	1 study	0 study
Homogeneous source of data	2 studies	2 studies	1 study
Low proportion of missing data	0 study	0 study	1 study
Weaknesses concluded by the authors of the selected studies
Missing data	11 studies	11 studies	8 studies
Small sample size	3 studies	3 studies	9 studies
Patients treated with obsolete methods	4 studies	4 studies	3 studies
Heterogeneous source of data	3 studies	3 studies	0 study
Selection bias	2 studies	2 studies	0 study
Short-time follow-up	1 study	1 study	0 study