The Yield of Routine Cardiac Imaging in Breast Cancer Patients Receiving Trastuzumab-Based Treatment: A Retrospective Cohort Study

Background: There are limited data on the yield of routine cardiac imaging for trastuzumab-treated patients with breast cancer. Methods: We conducted a retrospective cohort study of patients with breast cancer treated with adjuvant trastuzumab between 2007 and 2012 at Princess Margaret Cancer Centre (Toronto, Canada). We classified imaging tests as clinically prompted or routinely ordered and determined whether each test led to changes in patient care. A generalized estimating equation model was used to determine if pa-tient characteristics predicted routine studies more likely to change care. We analysed routine tests that were exclusively preceded by consecutive tests that did not change care to determine if their yield differed by time since trastuzumab start and the number of prior tests that did not change care. Results: We identified 448 patients who received 1735 cardiac im-aging studies after trastuzumab initiation. Of 1555 routine tests, 44 led to changes in care (2.8%) for 43 patients, whereas 50 of 180 clinically prompted tests (27.8%) altered care in 29 patients (P-value < 0.001). Earlier stage cancer, diabetes, prior anthracyclines, and prior cardiovascular disease were associated with a higher likelihood of changes in care following routine tests (P-value 0.05). Among routine tests that were exclusively preceded by consecutive tests that did not change care, tests ordered outside months 3-9 and those that followed >= 3 tests were even less likely to change care. Conclusions: Routine cardiac imaging tests rarely changed care for trastuzumab-treated patients with breast cancer, particularly among lower risk anthracycline-naive women who had multiple prior tests that did not change care.