Table 1. Multivariate Cox proportional hazard model clustered by patients.

	HROS	95% CIOS	POS	HRCMSS	95% CICMSS	PCMSS
Synchronous MPM	2.213	2.087–2.346	<0.0001	1.980	1.776–2.207	<0.0001
Age at diagnosis	1.088	1.086–1.091	<0.0001	1.054	1.050–1.059	<0.0001
Year of diagnosis	0.993	0.990–0.996	<0.0001	0.987	0.979–0.995	0.001
Sex	1.341	1.277–1.408	<0.0001	1.427	1.301–1.566	<0.0001

Note:

HR, hazard ratio; CI, confidence interval; OS, overall survival; CMSS, cutaneous melanoma specific survival; MPM, multiple primary cutaneous melanoma.