Persistent reduction in global longitudinal strain in the longer term after radiation therapy in patients with breast cancer

Abstract

Background: More than 80% of breast cancer patients receive radiotherapy (RT). However, RT can lead to cardiotoxicity, which usually develops insidiously over years, making diagnosis difficult. It is also unknown whether early identification of at-risk patients might improve long-term outcome. We have previously described subclinical alterations, detected by two-dimensional speckle tracking strain echocardiography, in left ventricular (LV) function immediately following RT in breast cancer.

Hypothesis: Subclinical myocardial alterations in LV function consequent to RT cardiotoxicity, observed early, persist at 12 months.

Methods: 40 chemotherapy naive women with left-sided breast cancer, treated with surgery and adjuvant breast RT, were prospectively recruited from two tertiary hospitals. Transthoracic echocardiography was performed at baseline (pre-RT), 6 weeks post-RT, and 12 months post-RT.

Results: An increase in LV end diastolic and end systolic volumes was seen from baseline, consistent with persistent LV remodelling; however, due to the increase in both systolic and diastolic volumes over time, no change in LV ejection fraction (EF) was observed. Global longitudinal strain (GLS) and S' velocity remained significantly lower at 12 months post-RT. GLS dropped by >10% in 16 patients and by >20% in 4 patients compared to baseline.

Conclusions: Subclinical cardiac dysfunction using strain analysis, evident early, persists one year after RT, despite unchanged conventional indices such as LVEF. Persistent GLS reduction may be of particular importance in breast cancer patients receiving concomitant chemotherapy. Longer term prospective studies are required to determine if reductions in strain post-RT are associated with future adverse cardiovascular events.

Keywords: Breast cancer; Cardiotoxicity; Longitudinal strain; Radiotherapy.