Trastuzumab therapy in Australia: which patients with HER2+ metastatic breast cancer are assessed for cardiac function?

PURPOSE: To manage the potential trastuzumab mediated cardiotoxicity, clinical guidelines recommend pre-treatment cardiac function assessment and 3-monthly reassessment during therapy. This study examined rates of cardiac function assessment and predictors of assessment among patients receiving trastuzumab for HER2+ metastatic breast cancer treatment in routine clinical care.

METHODS

Our cohort comprised 3418 women receiving trastuzumab for HER2+ metastatic breast cancer under Australia's nationally funded Herceptin Program (2001-2010). We examined rates of pre-treatment and during-treatment assessment. We used logistic regression and zero-inflated Poisson regression to examine predictors of pre-treatment and during-treatment assessment respectively.

RESULTS

37.7% of patients were assessed pre-treatment, 50.4% during therapy, and 26.4% both before and during therapy. Among patients assessed for cardiac function, reassessment occurred regularly (median of 3.9 months). History of cardiovascular conditions and prior anthracycline use predicted pre-treatment assessment (OR = 1.32, 95% CI: 1.08-1.61; OR = 1.23, 95% CI: 1.05-1.44 respectively). Concurrent trastuzumab and taxane use, exposure to anthracyclines, and older age predicted during-treatment assessment (IRR = 1.17, 95% CI: 1.06-1.29; IRR = 1.12, 95% CI: 1.02-1.23; and IRR = 1.05, 95% CI: 1.01-1.09 respectively). Patients with multi-morbidities were less likely to receive during-treatment assessment.

CONCLUSION

Over the last decade, cardiac function assessment in a large cohort of patients receiving trastuzumab was not consistent with guideline recommendations. The association between cardiac monitoring and risk factors for cardiac dysfunction suggest clinicians are triaging patients prior to implementing cardiac assessment. Efforts are needed to identify barriers to implementing current guidelines for cardiac monitoring in metastatic breast cancer patients undergoing trastuzumab treatment, particularly those with multi-morbidities.