Impact of physician and center case volume on the adequacy of cardiac monitoring during adjuvant trastuzumab in breast cancer.

Abstract

128 Background: A recent study suggests that cardiotoxicity from adjuvant trastuzumab (T-mab) is associated with inadequate cardiac monitoring (Ng et al. SABCS 2012). Few studies have examined the impact of centre or physician (MD) case volume (vol) on the quality of care in systemic therapy, including the adequacy of cardiac monitoring during T-mab treatment. Methods: All breast cancer patients treated with adjuvant T-mab in Ontario between 2003-2009 were identified through a provincial drug funding program. Patient demographics, hospitalizations, cardiac risk factors, cardiac imaging, comorbidities, treatment centres and MDs were ascertained. Annual case vol was calculated as the number of patients treated per year with adjuvant T-mab by each MD and centre. Cumulative case vol was calculated as the total number of patients treated with adjuvant T-mab. Centre and MD vol were divided into terciles (T1, T2 and T3) by the year of diagnosis. Inadequate cardiac monitoring was defined as per recent guidelines and per Ng et al. Hierarchical multivariable logistic regression models were constructed to examine factors associated with inadequate cardiac monitoring. Results: Our cohort consisted of 3,777 patients, 214 MDs and 68 centres. Of the total patients, 16.5% were over age 65; 30.3%, 9.4%, and 1.2% had previous diagnoses of hypertension, diabetes, and heart failure (HF), respectively; 24.3% did not receive adequate cardiac monitoring. Inadequate cardiac monitoring was associated with lower cumulative MD vol (T1: 27.9%, T2: 23.3%, T3: 20.8%, p < 0.0001) and lower annual centre vol (T1: 32.5%, T2: 19.7%, T3: 20.7%, p < 0.0001) in univariate analyses, and remained significant after adjusting for age, comorbidities, previous HF, socioeconomic status based on income, rural residence and calendar period. After adjusting for patient clustering at the MD, centre, and regional levels, lower cumulative MD vol (p=0.012), but not annual centre vol, remained a significant predictor for inadequate cardiac monitoring. Conclusions: Our findings suggest improved cardiac monitoring with greater MD experience, supporting the notion of centralization of systemic therapy to high vol MDs to optimize outcomes.