Table 1. Patients baseline characteristics.

	Total (n = 53)	OR+Group (n = 19)	OR-PD+Group (n = 20)	OR-PD−Group (n = 14)
Age (years)
Median (range)	64 (27–90)	65 (35–82)	64 (31–90)	61,5 (27–82)	P = 0.837
Sex
Female	24 (45.3%)	11 (57.9%)	7 (35.0%)	6 (42.9%)	P = 0.204
Male	29 (54.7%)	8 (42.1%)	13 (65.0%)	8 (57.1%)
Stage
III non-resectable	11 (20.8%)	4 (21.1%)	3 (15.0%)	4 (28.6%)	P = 0.793
IV	42 (79.2%)	15 (78.9%)	17 (85.0%)	10 (71.4%)
Somatic mutation
BRAF (codon 600)	24 (45.3%)	7 (36.8%)	9 (45.0%)	8 (57.1%)	P = 0.621
NRAS (exon 2 or 3)	29 (54.7%)	12 (63.2%)	11 (55.0%)	6 (42.8%)
Tumor thickness (mm)
Mean ± SD	3.04 ± 2.20	2.78 ± 1.25	3.23 ± 2.83	3.08 ± 2.25	P = 0.971
Ulceration
No	21 (39.6%)	6 (31.6%)	10 (50.0%)	5 (35.7%)	P = 0.346
Yes	15 (28.3%)	5 (26.3%)	4 (20.0%)	6 (42.9%)
Unknown	17 (32.1%)	8 (42.1%)	6 (30.0%)	3 (21.4%)
Treatment
Nivolumab	49 (92.5%)	17 (89.5%)	19 (95.0%)	13 (92.9%)	P = 0.788
Nivo + Ipilimumab	4 (7.5%)	2 (10.5%)	1 (5.0%)	1 (7.1%)
Previous treatment
None (1st line)	26 (49.1%)	11 (57.9%)	9 (45.0%)	6 (42.9%)	P = 0.664
Chemotherapy	2 (3.8%)	1 (5.3%)	1 (5.0%)	0
Immunotherapy	5 (9.4%)	3 (15.8%)	1 (5.0%)	1 (7.1%)
Targeted therapy	20 (37.7%)	4 (21.0%)	9 (45.0%)	7 (50.0%)
Number of metastatic sites
Mean ± SD	4.7 ± 3.3	4.4 ± 3.3	5.3 ± 3.4	4.2 ± 3.4	P = 0.340
Baseline LDH (UI/L)
Mean ± SD	246 ± 222	185 ± 66	255 ± 149	314 ± 385	P = 0.319
ctDNA detectability
Detectable ctDNA	23 (43.4%)	6 (31.6%)	11 (55.0%)	6 (42.8%)	P = 0.337
Undetectable ctDNA	30 (56.6%)	13 (70.4%)	9 (45.0%)	8 (57.2%)
ctDNA concentration (mutated copies/mL)
Mean ± SD	857 ± 3695	91 ± 195	581 ± 1079	2291 ± 7047	P = 0.330