Permanent longitudinal strain damage of cardiotoxic drugs in childhood cancer: What is the safe level?

Objective: Anthracycline administration in children is associated with cardiac dysfunction. Speckle-tracking echocardiography (STE) can detect subclinical cardiac damage that may go undetected by conventional two-dimensional (2D) echocardiography. This study aims to investigate medium-term anthracycline cardiotoxicity using STE and determine a safer administrable level of anthracyclines (ACs).

Methods: This observational case-control study enrolled 37 healthy controls and 78 pediatric cancer survivors who received chemotherapy. The patients were divided into two groups: cardiotoxic received (CR) and cardiotoxic free (CF). Data on segmental longitudinal strain (LS), global LS (GLS), and 2D echocardiographic parameters were collected after a drug-free period of at least one year.

Results: A total of 115 children with a mean age of 108 ± 55 months, of whom 66% were males, were included in the study. Both the groups of cancer survivors exhibited significantly reduced GLS compared to healthy controls (CR vs. controls, P = 0.001; CF vs. controls, P = 0.013), but no significant difference in left ventricular ejection fraction (LVEF) was observed (P = 0.75). Overall, cancer survivors treated with ACs demonstrated a significant reduction in strain in 10 left ventricular segments, particularly in the basal segments (P < 0.05). Among CR patients, those with impaired GLS (n = 43, GLS worse than -21.9) had significantly higher mean age and cumulative anthracycline dose compared to CR patients with normal GLS (age, P = 0.024; anthracycline dosage, P = 0.036). Using an anthracycline cutoff of 223 mg/m² resulted in a higher detection rate (49% vs. 25%) and fewer missed cases (51% vs. 74%) compared to the 360 mg/m² anthracycline cutoff.

Conclusion: Childhood cancer survivors demonstrate significantly reduced GLS while preserving a normal LVEF, which does not differ significantly from reference values of healthy children. The reduction in strain appears to be associated with higher anthracycline doses and older age. Lowering the anthracycline threshold to 223 mg/m² may improve the predictability of a decline in cardiac function using strain imaging at medium-term follow-up.