Table 3.

Significance of each variable included in the mixed effects Cox models.

Clinical model					Treatment-adjusted model
Covariates	Rank	AIC	LRT	P-value	Covariates	Ran k	AIC	LRT	P-value
Hospital	1	130132	65.61	<0.0001	Hospital	1	129913.1	80.4	<0.0001
Stage	2	129653.44	820.99	<0.0001	Stage	2	129068.52	682.85	<0.0001
Year	3	129253.6	425.15	<0.0001	Year	3	128732.12	356.45	<0.0001
Age	4	128988.4	151.94	<0.0001	Brachytherapy	4	128670.9	281.23	<0.0001
Race	5	128926.02	89.55	<0.0001	Chemotherapy	5	128536.3	148.64	<0.0001
Insurance status	6	128911.56	77.1	<0.0001	Race	6	128473.24	89.57	<0.0001
Histology	7	128890.16	51.7	<0.0001	Age	7	128461.02	77.36	<0.0001
Grade	8	128888.34	49.88	<0.0001	Grade	8	128439.54	53.88	<0.0001
Hospital volume	9	128849.1	6.65	0.01	Insurance status	9	128436.56	54.89	<0.0001
Hospital type	10	128841.56	1.11	0.57	Histology	10	128431.18	45.51	<0.0001
Hospital region	11	128840.86	2.41	0.49	Hospital volume	11	128391	1.32	0.25
					Hospital type	12	128388.38	0.71	0.70
					Hospital Region	13	128386.08	0.41	0.94

AIC, Alkaike information criterion. LRT, likelihood ratio test.

The null model has an AIC of 114468.18. AIC was calculated as minus twice log likelihood plus 2 df. The LRT compares the full model (including all variables) with a reduced model omitting 1 variable at a time. The higher the AIC, the greater importance of the omitted variable.