Table 1

Baseline characteristics stratified by ICI

Characteristic	Total	Single-agent anti-PD-1	Single-agent anti-CTLA-4	Combination anti-PD-1/anti-CTLA-4	Combination anti-PDL-1/MEK inhibitor
Characteristic	n (%) or median (range)	n (%) or median (range)	n (%) or median (range)	n (%) or median (range)	n (%) or median (range)
Sex
Female	27 (50)	20 (50)	5 (63)	2 (40)	0
Male	27 (50)	20 (50)	3 (38)	3 (60)	1 (100)
Age when commenced ICI treatment, years (range)	75 (26–94)	78 (26–94)	68 (34–89)	69 (58–79)	75 (75)
Site of primary
Lower limb	34 (63)	25 (63)	5 (63)	3 (60)	1 (100)
Trunk	3 (6)	2 (5)	1 (13)	0	0
Upper limb	3 (6)	3 (8)	0	0	0
Head/neck	9 (17)	6 (15)	1 (13)	2 (40)	0
Unknown	5 (9)	4 (10)	1 (13)	0	0
Primary tumor thickness, mm (range)	3 (0.6–40)	3 (0.6–40)	2.9 (1.2–8)	2.4 (1–3.9)	9 (9)
Ulcerated primary tumor
Yes	15 (28)	12 (30)	2 (25)	1 (20)	0
No	34 (63)	24 (60)	5 (63)	4 (80)	1 (100)
Unknown	5 (9)	4 (10)	1 (13)	0	0
BRAF
Mutation	10 (19)	6 (15)	3 (38)	1 (20)	0
Wildtype	42 (78)	32 (80)	5 (63)	4 (80)	1 (100)
Untested	2 (4)	2 (5)	0	0	0
NRAS
Mutation	15 (28)	10 (25)	3 (38)	2 (40)	0
Wildtype	19 (35)	12 (30)	4 (50)	2 (40)	1 (100)
Untested	20 (37)	18 (45)	1 (13)	1 (20)	0
AJCC 8th edition stage at time of ICI
IIIB	12 (22)	9 (23)	3 (38)	0	0
IIIC	40 (74)	30 (75)	4 (50)	5 (100)	1 (100)
IIID	2 (4)	1 (3)	1 (13)	0	0
No of lesions when treated with ICI
1	19 (35)	16 (40)	2 (25)	1 (30)	0
02/05/20	11 (20)	7 (18)	1 (13)	3 (60)	0
>5	20 (37)	15 (38)	3 (38)	1 (20)	1 (100)
Unknown	4 (7)	2(5)	2 (25)	1	0
Concurrent nodal disease at time of ICI treatment
Yes	35 (65)	26 (65)	5 (63)	4 (80)	0
No	19 (35)	14 (35)	3 (38)	1 (20)	1 (100)