Introduction: Global longitudinal strain (GLS) can predict cancer therapeutics-related cardiac dysfunction (CTRCD) and guide initiation of cardioprotection (CPT) at the time of chemotherapy. No prospective randomized controlled trial (RCT) has identified the impact on LV function in survivors. Hypothesis: GLS-guided CPT provides less cardiac dysfunction in survivors of potentially cardiotoxic chemotherapy, compared with usual care. Methods: In this international (28 sites) multicenter prospective RCT, patients (pts) were included if they were administrated anthracyclines and had another risk factor for HF. They were randomly allocated into undergoing GLS-guided CPT for >12% relative reduction in GLS or EF-guided CPT for >10% absolute reduction of EF. Primary endpoint was the change in EF (ΔEF) from baseline to 3 years by 3D echocardiography. Results: Among 331 pts enrolled, 255 (77%, 60±16 years, 95% women) completed 3-year follow-up (123 in EF-guided group and 132 in GLS-guided). Most had breast cancer (236, 93%), 67 (26%) with hypertension and 32 (13%) with diabetes mellitus. A regimen of anthracycline and trastuzumab was the most common chemotherapy regimen (84%). The baseline LVEF was 61±4% with GLS of 20.7±2.3% in the entire population. CPT was administrated in 18 pts (15%) in EF-guided and 41 (31%) in GLS-guided (p=0.02). Most patients showed recovery in EF and GLS after chemotherapy (Figure). ΔEF was -2.0±4.8 in EF-guided and -1.4±5.4 in GLS-guided (p=0.25), but LVEF at 3 years in EF-guided was lower than that of GLS-guided (58.0±5.6% vs 59±4.9%, p=0.043). Ten pts in EF-guided developed CTRCD, and 6 in GLS-guided (p=0.24). Conclusions: Most of the enrolled pts were taking potentially cardiotoxic chemotherapy for breast cancer. Almost all improved LV function over 3 years, and although GLS-guided CPT was associated with higher EF at 3 years, there was no difference in ΔEF compared with EF-guided surveillance.