Table 2.

Patients clinico-pathological characteristics according to metformin use (n = 382).

Variable		Metformin
		No		Yes		Total		χ2
		N	Column %	N	Column %	N	Column %	p
Sex	Male	207	60.3%	15	38.5%	222	58.1%	0.009
	Female	136	39.7%	24	61.5%	160	41.9%
Age at diagnosis	<50	66	19.2%	1	2.6%	67	17.5%	0.017
	50–59	53	15.5%	2	5.1%	55	14.4%
	60–69	66	19.2%	10	25.6%	76	19.9%
	70–79	106	30.9%	17	43.6%	123	32.2%
	≥80	52	15.2%	9	23.1%	61	16.0%
Charlson comorbidity index (without diabetes)	0	277	80.8%	30	76.9%	307	80.4%	0.537
	1	46	13.4%	7	17.9%	53	13.9%
	2	12	3.5%	0	0.0%	12	3.1%
	3	6	1.7%	2	5.1%	8	2.1%
	4	1	0.3%	0	0.0%	1	0.3%
	5	1	0.3%	0	0.0%	1	0.3%
Charlson comorbidity index (without diabetes)	0	277	80.8%	30	76.9%	307	80.4%	0.568
	≥1	66	19.2%	9	23.1%	75	19.6%
BMI	Underweight	1	0.3%	0	0.0%	1	0.3%	<0.001
	Normal weight	96	28.0%	3	7.7%	99	25.9%
	Overweight	124	36.2%	14	35.9%	138	36.1%
	Obesity	74	21.6%	20	51.3%	94	24.6%
	N/A	48	14.0%	2	5.1%	50	13.1%
BMI	Under-normal weight	97	28.3%	3	7.7%	100	26.2%	0.002
	Overweight–obese	198	57.7%	34	87.2%	232	60.7%
	N/A	48	14.0%	2	5.1%	50	13.1%
Statin	No	282	82.2%	29	74.4%	311	81.4%	0.232
	Yes	61	17.8%	10	25.6%	71	18.6%
ASA	No	274	79.9%	25	64.1%	299	78.3%	0.024
	Yes	69	20.1%	14	35.9%	83	21.7%
Localization ICDO-3	C44.0 Lip skin	1	0.3%	1	2.6%	2	0.5%	0.445
	C44.1 Eyelid	16	4.7%	2	5.1%	18	4.7%
	C44.2 Outer ear	54	15.7%	5	12.8%	59	15.4%
	C44.3 Other parts of the face	164	47.8%	18	46.2%	182	47.6%
	C44.4 Scalp and neck	108	31.5%	13	33.3%	121	31.7%
Localization	Scalp and neck	108	31.5%	13	33.3%	121	31.7%	0.814
	Face	235	68.5%	26	66.7%	261	68.3%
AJCC stage	IA	185	53.9%	20	51.3%	205	53.7%	0.590
	IB	59	17.2%	10	25.6%	69	18.1%
	II	81	23.6%	7	17.9%	88	23.0%
	III	18	5.2%	2	5.1%	20	5.2%
AJCC stage	I	244	71.1%	30	76.9%	274	71.7%	0.447
	II + III	99	28.9%	9	23.1%	108	28.3%
Tumor thickness (mm)	<1	204	59.5%	24	61.5%	228	59.7%	0.938
	1–2	57	16.6%	6	15.4%	63	16.5%
	2–4	37	10.8%	5	12.8%	42	11.0%
	>4	45	13.1%	4	10.3%	49	12.8%
Tumor size (TNM)	1	209	60.9%	25	64.1%	234	61.3%	0.752
	2	60	17.5%	6	15.4%	66	17.3%
	3	32	9.3%	5	12.8%	37	9.7%
	4	42	12.2%	3	7.7%	45	11.8%
Nodal status (TNM)	0	325	94.8%	37	94.9%	362	94.8%	0.975
	1	18	5.2%	2	5.1%	20	5.2%
Ulceration	No	270	78.7%	33	84.6%	303	79.3%	0.625
	Yes	70	20.4%	6	15.4%	76	19.9%
	N/A	3	0.9%	0	0.0%	3	0.8%
Histological subgroup	Lentigo-maligna melanoma	140	40.8%	14	35.9%	154	40.3%	0.555
	Nodular melanoma	53	15.5%	6	15.4%	59	15.4%
	Superficial spreading melanoma	106	30.9%	16	41.0%	122	31.9%
	Melanoma n. o. s. and other	44	12.8%	3	7.7%	47	12.3%
Surgical margin (mm)	<5	86	25.1%	7	17.9%	93	24.3%	0.152
	5–9	131	38.2%	13	33.3%	144	37.7%
	≥10	125	36.4%	18	46.2%	143	37.4%
	N/A	1	0.3%	1	2.6%	2	0.5%
Neck dissection	No	316	92.1%	36	92.3%	352	92.1%	0.969
	Yes	27	7.9%	3	7.7%	30	7.9%
Adjuvant radiotherapy	No	339	98.8%	39	100.0%	378	99.0%	0.498
	Yes	4	1.2%	0	0.0%	4	1.0%
Adjuvant chemo/immunotherapy	No	326	95.0%	38	97.4%	364	95.3%
	Yes	17	5.0%	1	2.6%	18	4.7%	0.504
	Total	343	100.0%	39	100.0%	382	100.0%

N: number of subjects; %: percentage of subjects.