Multinomial logistic regression predicting treatment in a low vs. high immunotherapy prescribing hospital (accounting for the middle quintiles)

	Relative risk ratio	95% Confidence Interval	p-value
Age
≤ 30	Ref.
41–50	1.04	0.20–5.32	0.964
51–60	0.84	0.17–4.18	0.834
61–70	1.28	0.25–6.49	0.766
71–80	1.19	0.25–5.68	0.831
81–90	2.24	0.46–10.9	0.318
Gender
male	Ref.
female	0.86	0.62–1.18	0.346
Race
White	Ref.
Black	0.36	0.11–1.14	0.081
Other/unknown	1.97	0.71–5.46	0.193
Year of Diagnosis
2011	Ref.
2012	1.28	0.82–2.01	0.287
2013	1.08	0.69–1.70	0.728
2014	1.40	0.89–2.22	0.147
2015	1.83	1.17–2.87	0.008
Charlson Deyo Index
0	Ref.
1	1.11	0.73–1.71	0.623
2	1.30	0.50–2.21	0.888
> =3	1.93	0.77–4.87	0.162
Primary Site
Head and Neck	Ref.
trunk	1.41	0.74–2.71	0.294
extremities	1.30	0.72–2.33	0.379
overlapping	1.25	0.60–2.63	0.550
Histology
Melanoma, NOS	Ref.
nodular	0.78	0.44–1.39	0.396
Lentigo	0.35	0.04–3.44	0.369
superficial	0.87	0.38–2.00	0.749
Acral	0.47	0.07–3.01	0.424
other	0.91	0.43–1.93	0.798
Metastatic stage
M1, NOS	Ref.
M1a	0.42	0.15–1.17	0.097
M1b, lung	0.39	0.14–1.10	0.075
M1c, visceral	0.22	0.08–0.62	0.004
Brain involvement	0.44	0.15–1.23	0.116
Ulceration
No ulceration	Ref.
ulceration	0.88	0.54–1.46	0.631
unknown	0.63	0.35–1.15	0.132
Breslow (continuous)	1.00	1.00–1.00	0.141
Insurance
Private	Ref.
Medicare	1.13	0.74–1.71	0.576
Medicaid	2.10	1.12–3.92	0.020
Other	1.11	0.34–3.63	0.850
No insurance	2.44	1.28–4.67	0.007
unknown	0.28	0.07–1.16	0.080
Income*
≥ $63,000	Ref.
$48,999–$62,999	1.25	0.65–2.40	0.509
$38,000–$47,999	0.93	0.36–2.41	0.887
< $38,000	1.71	0.57–5.14	0.339
unknown	0.29	0.02–3.54	0.333
Education,*
≥ 21%	Ref.
13%-20,9%	1.14	0.55–2.37	0.730
7–12,9%	0.97	0.40–2.33	0.943
< 7%	0.61	0.21–1.76	0.360
unknown	6.10	0.38–98.55	0.203
Distance
< 12.5mi	Ref.
12.5-50mi	0.58	0.38–0.88	0.011
≥ 50mi	0.14	0.07–0.30	< 0.001
unknown	0.38	0.07–2.23	0.285
Facility Location
Northeast	Ref.
South	5.06	0.98–26.03	0.052
Midwest	0.97	0.15–6.06	0.973
West	1.81	0.35–9.30	0.475
Facilitytype
Academic	Ref.
CCCP	5.18	1.69–15.88	0.004
INCP	6.60	1.06–41.14	0.043
County
Metro	Ref.
Urban	2.58	1.34–4.96	0.005
Rural	1.93	0.32–11.74	0.476
unknown	1.25	0.45–3.45	0.671

Abbreviations: NOS = not otherwise specified, mi = miles; CCCP = comprehensive community cancer program; INCP = integrated network cancer program

Significant p-values in italic

*ZIP-code level variable

**Percentage of residents in home county with no high school degree from 2012 American County Survey Data