Table 2: Annual hospital volume in relation to insufficient cardiac monitoring and cardiotoxicity in patients with breast cancer who underwent treatment with adjuvant trastuzumab in Ontario from 2003 to 2009 (n = 3777)

Outcome	Annual hospital volume, OR (95% CI)			p value
Outcome	Tercile 1	Tercile 2	Tercile 3	p value
Insufficient monitoring
Model 1*	1 (Reference)	1.01 (0.75-1.36)	1.15 (0.75-1.77)	0.8
Cardiotoxicity
Model 1*	1 (Reference)	0.72 (0.56-0.92)	0.75 (0.56-1.01)	0.02
Model 2†	1 (Reference)	0.93 (0.68-1.27)	0.74 (0.49-1.12)	0.3

Note: OR = odds ratio, tercile 1 = low, tercile 2 = medium, tercile 3 = high.

*Model 1 was adjusted for age, Charlson-Deyo index, previous heart failure, hypertension, previous myocardial infarction, diabetes mellitus, income, rural residence, cumulative physician volume, calendar period of treatment, hospital clustering, physician clustering and Local Health Integration Network clustering.

†Model 2 was adjusted for all variables in model 1 and further adjusted for sufficiency of cardiac monitoring.