Cardiac safety of reduced surveillance for cancer therapy related cardiac dysfunction in patients with breast cancer treated with HER2-targeted therapy

12083 Background: Non-anthracycline-based therapy is a treatment option for patients (pts) with HER2-positive breast cancer (BC) and is associated with lower risk of cancer therapy related cardiac dysfunction (CTRCD) compared to anthracycline-based treatment. Given the reduced CTRCD risk with non-anthracycline HER2-targeted therapies, updates to practice guidelines that recommend surveillance echocardiograms (TTE) every 3 months are needed. We evaluated the cardiac safety of reduced CTRCD surveillance in pts receiving non-anthracycline HER2-targeted therapies. Methods: Pts with BC treated with non-anthracycline HER2-targeted therapy were enrolled in this single-arm prospective study. Pts with previous anthracycline exposure, uncontrolled hypertension (systolic blood pressure ≥ 160 mmHg), or significant cardiovascular disease were excluded. TTEs were performed at baseline, 6 months, and 12 months during HER2-targeted treatment. The primary endpoint was a cardiac event, defined by clinical heart failure (New York Heart Association Class III/IV) or cardiovascular death, with a prespecified non-inferiority margin of 2.9% relative to a cardiac event rate of 1.1% based upon prior studies. Secondary endpoints were CTRCD, defined by decline of left ventricular ejection fraction (LVEF) ≥10% to < 53%, and interruption of HER2-targeted treatment secondary to CTRCD. Results: Between May 2019 and January 2022, 190 pts (age 52 ± 11 y) with HER2-positive BC were enrolled: 143 (75%) had stage I disease, 8 (4%) had diabetes, 38 (20%) had hypertension, and baseline LVEF was 64 ± 5% (Table). Additional TTEs outside the prespecified 6- and 12-month timepoints were performed for 35 (18%) pts, of which 20 were to assess for possible cardiac symptoms. After 1-year follow-up, there were 0 (0%; 97.5% CI 0- 1.9%) cardiac events. Two (1.1%) pts developed CTRCD and 1 (0.5%) pt had a temporary CTRCD-related treatment interruption. Conclusions: Reduced CTRCD surveillance every 6 months is feasible and safe for selected pts with HER2-positive BC receiving non-anthracycline HER2-targeted therapy. Our findings support the need to update cardio-oncology practice guidelines and allow for less frequent surveillance TTEs among pts at low-risk for CTRCD. Clinical trial information: NCT03983382 . [Table: see text]