Lack of Uniformity in Cardiac Assessment during Trastuzumab Therapy

Adjuvant therapy with trastuzumab is standard in women with early stage HER-2-positive breast cancer. Following reports of left ventricular (LV) dysfunction with trastuzumab in metastatic disease, trials of adjuvant trastuzumab specified LV monitoring schedules. This study analyzes the pattern of cardiac testing and the incidence of heart failure (HF) in women treated with adjuvant trastuzumab in a real-world setting. De-identified medical and pharmacy claims data for women <65 years of age who began trastuzumab therapy between January 1, 2007 and December 31, 2007 were obtained from an integrated database at Medco Health Solutions, Inc. Patients receiving trastuzumab for ≥90 days were assessed for compliance with standard LV testing, defined as testing at baseline, at 4-month intervals, and at the end of trastuzumab therapy. Cardiac risk factors and HF were identified by ICD-9-CM diagnosis codes, by medical claims, and by pharmacy claims for drugs used to treat diabetes, hypercholesterolemia, or HF. A total of 631 women received trastuzumab ≥30 days, and 585 continued for ≥90 days (median duration 356 days [±1Q = 322-378]). Seventy nine patients had no LV tests. Ninety three were fully compliant with baseline, interval, and final testing. Seven women were identified as having new-onset HF. In this retrospective analysis, clinicians did not routinely follow LV testing protocols used in clinical trials or published recommendations. As breast cancer specific survival rates improve, the long-term contribution of cardiotoxic therapies to cardiac morbidity and mortality in survivors will gain attention. Early efforts to ensure compliance with testing could contribute to use of preventive therapies to mitigate future long-term consequences.