. 2023 Sep 28;13(9):e073306. doi: 10.1136/bmjopen-2023-073306

Table 3.

Model development

Citation	Sample size	Follow-up period	End point	Events (n)	Candidate selection method	Final predictor selection	Final predictors (n)	Validation method
Baade et al²⁵	28 654	Median=7.2 years (86.4 months)	MSS	1700	Prespecification from existing data	Backward elimination	7	Internal-external cross validation
Balch et al²⁶	13 581	5–20 years	MSS	NR	Unclear	Unclear	8	External—geographic
Cochran et al²⁷	1042	Median=42.5 months	OS	NR	Prespecification+univariate analysis	Backward elimination	5	Internal sample validation
Cochran et al²⁷	1042	Median=42.5 months	Recurrence	NR	Prespecification+univariate analysis	Backward elimination	4	Internal sample validation
El Sharouni et al²⁸	DEV: 25 930 VALID: 2968	DEV: Median=6.7 years VALID: Median=12 years	LRFS	232	Prespecification from existing data	Backward elimination	6	Internal-external cross validation
El Sharouni et al²⁸	DEV: 25 930 VALID: 2968	DEV: Median=6.7 years VALID: Median=12 years	RRFS	564	Prespecification from existing data	Backward elimination	7	Internal-external cross validation
El Sharouni et al²⁸	DEV: 25 930 VALID: 2968	DEV: Median=6.7 years VALID: Median=12 years	DRFS	278	Prespecification from existing data	Backward elimination	6	Internal-external cross validation
Fonseca et al²⁹	259	Median=80.13 months	DRFS	117	Univariate analysis	Backward elimination	5	Bootstrap
Fonseca et al²⁹	259	Median=80.13 months	MSS	117	Univariate analysis	Backward elimination	5	Bootstrap
Gimotty et al³¹	DEV: 884 VALID: 114	At least 10 years	Metastasis	127	Multivariate analysis	Backward elimination	4	External—new cohort
Gimotty et al³⁰	DEV: 26 114	Median=4.6 years	OS	3593	Prespecification from existing data	Full model approach	4	External—geographic
Gimotty et al³⁰	VALID: 2389	Median=8.1 years	OS	1076	Prespecification from existing data	Full model approach	5	External—geographic
Maurichi et al³²	2243	124 months	12 year OS	240	Multivariate analysis	Full model approach	6	Congruence examination
Rosenbaum et al³³	DEV: 506 VALID: 149	Median=4.4 years	RFS	NR	Univariate analysis	Backward elimination	3	Internal k-fold validation
Soong et al³⁴	DEV: 14 760 VALID: 10 974	5 and 10 years	OS	NR	Multivariate analysis	Full model approach	6	External—geographic
Tsai et al³⁵	13 268	Not reported	OS	NR	Prespecification from existing data	Full model approach	6	Internal-external cross validation
Verver et al³⁶	3180	Median=61 months	Composite recurrence and/or MSM	Recurrence=496 Dead=277	Prespecification+univariate analysis	Backward elimination	3	Internal-external cross validation
Vollmer and Seigler³⁷	1910	Median=7.6 years	Mortality	NR	Prespecification	Full model approach	5	Internal k-fold validation
Xiao et al³⁸	DEV: 46 336 VALID: 19 856	3 and 5 years	OS	NR	Prespecification+univariate analysis	Full model approach	10	Internal sample validation

DEV, development set; DRFS, distant recurrence-free survival; EPV, events per variable; MSM, melanoma specific mortality; MSS, melanoma specific survival; NR, not reported; OS, overall survival; RFS, recurrence free survival; RRFS, regional recurrence free survival; VALID, validation set.