ST2 levels increased and were associated with changes in left ventricular systolic function during a three-year follow-up after adjuvant radiotherapy for breast cancer

OBJECTIVES: To search for biomarkers of RT-induced cardiotoxicity, we studied the behavior of ST2 during RT and three years after RT, and the associations with echocardiographic changes. MATERIALS AND METHODS: We measured soluble ST2 (ng/ml) in serum samples from 63 patients receiving RT for early breast cancer. Sampling and echocardiography were performed at baseline, after RT and at the three-year follow-up. Patients were grouped by >15% (group 1) and ≤15% (group 2) relative worsening in global longitudinal strain (GLS). RESULTS: ST2 levels tended to increase during RT, from a median (interquartile range; IQR) of 17.9 (12.4-22.4) at baseline to 18.2 (14.1-23.5) after RT (p = 0.075). By the three-year follow up, ST2 levels increased to 18.7 (15.8-24.2), p = 0.018. The increase in ST2 level was associated with worsening cardiac systolic function at three-year follow-up, GLS (rho = 0.272, p = 0.034) and left ventricular ejection fraction (LVEF) (rho = ─0.343, p = 0.006). Group 1 (n = 14) had a significant increase in ST2 levels from 17.8 (12.3-22.5) at baseline to 18.4 (15.6-22.6) after RT, p = 0.035 and to 19.9 (16.0-25.1) three years after RT, p = 0.005. ST2 levels were stable in group 2 (n = 47): 17.8 (12.3-22.0) at baseline, 17.7 (12.6-23.5) after RT and 18.0 (15.5-22.4) at three years. CONCLUSION: ST2 may be useful for determining which patients are at risk for long-term cardiovascular toxicity following adjuvant breast cancer RT, but prospective clinical studies are needed to confirm this hypothesis.