Abstract P5-18-14: Cardiac monitoring during adjuvant trastuzumab therapy for breast cancer

Cardiac assessment in Australian patients receiving (neo)adjuvant trastuzumab for HER2-positive early breast cancer: a population-based study

PURPOSE

Cardiac function assessment is important for detecting and managing trastuzumab-associated cardiotoxicity. Our study estimates rates and predictors of cardiac assessment among patients receiving trastuzumab for HER2-positive early breast cancer (HER2+EBC) in Australia.

METHODS

We conducted a retrospective cohort study of Australians initiating (neo)adjuvant trastuzumab for HER2+EBC between 1 January 2015 and 15 April 2019. We used administrative claims to determine the number of patients receiving guideline-recommended assessment, i.e. evidence of baseline cardiac assessment (between 120 days before and 30 days after trastuzumab initiation) and regular on-treatment cardiac assessments (at least every 120 days). We examined factors associated with baseline and regular on-treatment cardiac assessment.

RESULTS

Our study includes 5621 patients (median age 56 years), of whom 4984 (88.7%) had a baseline cardiac function test. Among 4280 patients with at least 12 months of follow-up, 2702 (63.1%) had guideline-recommended cardiac assessment. Rates of guideline-recommended assessment increased with later year of diagnosis (60.9% in 2015 vs 68.3% in 2018, OR 1.34, 95% CI 1.06-1.69). Patients with higher baseline comorbidities and greater socioeconomic disadvantage were less likely to have guideline-recommended cardiac assessment. Cardiac assessment practices varied by State/Territory. There was no association between baseline cardiac risk or anthracycline use and the likelihood of receiving guideline-recommended cardiac assessment.

CONCLUSION

The majority of patients receiving (neo)adjuvant trastuzumab had guideline-recommended baseline and on-treatment cardiac assessment. Variations in cardiac assessment predominantly related to system-level factors, such as year of diagnosis and geography, rather than individual patient factors.

Cardiac Monitoring During Adjuvant Trastuzumab-Based Chemotherapy Among Older Patients With Breast Cancer

PURPOSE

Patients treated with adjuvant trastuzumab require adequate cardiac monitoring. We describe the patterns of cardiac monitoring and evaluate factors associated with adequate monitoring in a large population-based study of older patients with breast cancer.

PATIENTS AND METHODS

Patients age 66 years or older with full Medicare coverage, diagnosed with stage I to III breast cancer between 2005 and 2009, and treated with adjuvant trastuzumab-based chemotherapy were identified in the SEER-Medicare and the Texas Cancer Registry-Medicare databases. The adequacy of cardiac monitoring was determined. Chemotherapy, trastuzumab use, cardiac monitoring, and comorbidities were identified by using International Classification of Diseases, 9th revision and Healthcare Common Procedure Coding System codes. Prescribing physician characteristics were also evaluated. Analyses included descriptive statistics and multilevel logistic regression models.

RESULTS

In all, 2,203 patients were identified; median age was 72 years. Adequate monitoring was identified in only 36.0% of the patients (n = 793). In the multivariable model, factors associated with optimal cardiac monitoring included a more recent year of diagnosis (hazard ratio [HR], 1.83; 95% CI, 1.32 to 2.54), anthracycline use (HR, 1.39; 95% CI, 1.14 to 1.71), female prescribing physician (HR, 1.37; 95% CI, 1.10 to 1.70), and physician graduating after 1990 (HR, 1.66; 95% CI, 1.29 to 2.12). The presence of cardiac comorbidities was not a determinant for cardiac monitoring. Of the variance in the adequacy of cardiac monitoring, 15.3% was attributable to physician factors and 5.2% to measured patient factors.

CONCLUSION

A large proportion of patients had suboptimal cardiac monitoring. Physician characteristics had more influence than measured patient-level factors in the adequacy of cardiac monitoring. Because trastuzumab-related cardiotoxicity is reversible, efforts to improve the adequacy of cardiac monitoring are needed, particularly in vulnerable populations.