Table 3 Time-to-event melanoma recurrence prediction by GB-T and RF-T models.

Data	Sample size	Validation	GB-T		RF-T
Data	Sample size	Validation	Time-dependent AUC	Concordance index	Time-dependent AUC	Concordance index
Original cohorts^a	MGB: 215 recurrences 645 non-recurrences DFCI: 95 recurrences 285 non-recurrences	Internal	0.853 CI^e:0.849–0.857	0.820 CI:0.816–0.824	0.845 CI:0.841–0.850	0.813 CI:0.809–0.816
		External	0.820 CI:0.819–0.821	0.809 CI:0.808–0.810	0.810 CI:0.809–0.811	0.807 CI:0.807–0.808
		p-value^d	<0.001	0.012	<0.001	0.248
Core complete cohorts^b	MGB: 142 recurrences 516 non-recurrences DFCI: 74 recurrences 276 non-recurrences	Internal	0.829 CI:0.819–0.840	0.788 CI:0.783–0.793	0.788 CI:0.783–0.793	0.783 CI:0.775–0.791
		External	0.804 CI:0.802–0.806	0.808 CI:0.807–0.810	0.781 CI:0.778–0.783	0.793 CI:0.791–0.795
		p-value^d	0.001	0.001	0.057	0.312
Complete cohorts^c	MGB: 116 recurrences 365 non-recurrences DFCI: 45 recurrences 175 non-recurrences	Internal	0.808 CI:0.800–0.816	0.768 CI:0.760–0.777	0.795 CI:0.786–0.804	0.769 CI:0.761–0.776
		External	0.673 CI:0.671–0.675	0.752 CI:0.75–0.753	0.675 CI:0.67–0.68	0.734 CI:0.732–0.736
		p-value^d	<0.001	0.007	<0.001	<0.001

^aThe original cohorts (Supplementary Table 5) in which there were no missing values for sex, insurance type, age at diagnosis, HPCM, histological type, tumor site, AJCC stage, Breslow thickness, anatomic level, and laterality (Supplementary Table 1).
^bThe “core complete” cohorts were based on the original cohorts with no missing values for additional core features: negative or not indicated regional lymph node histology, no missing value for ulceration, and no missing value for mitotic rate.
^cThe “complete” cohorts were based on the core complete cohorts with additional constraints: no missing values for median income and all tumor characteristics. Considering the small sample size for time-to-vent prediction, twofold cross-validation was used for internal validation.
^dp-value: comparison between the internal validation and the external validation.
^eCI: 95% confidence interval.

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