Cardiac toxicity is a potential side effect following radiotherapy (RT) to the chest.¹,² For left-sided breast cancer RT, Deep Inspiration Breath Hold (DIBH) has proved to be a very advantageous means of reducing RT doses to the heart as measured by planning dosimetry. This is especially pronounced when compared with free-breathing (FB).2,3 Our study aimed to investigate whether the dosimetric improvements as seen on RT treatment planning system Dose Volume Histograms, translated into improvements in clinical outcomes as measured by Echocardiography strain imaging.
Forty patients treated with curative intent adjuvant RT for left-sided breast cancer were prospectively recruited into the study. Echocardiography strain imaging was conducted at baseline, and at six months post RT completion. Ten patients were treated in FB, while 30 patients were treated in DIBH.
Standard echo and strain parameters were measured, with Left Ventricular Global Longitudinal Strain (LVGLS) analysed to investigate any cardiac dysfunction between the FB and DIBH groups.
Baseline comparisons showed no significant differences between the two groups in terms of Left Ventricular (LV) volume, ejection fraction, and GLS (p >0.2). LVGLS was impaired in both patient cohorts. There was a significant difference in LVGLS over time between the two groups (p <0.05). LVGLS worsened as FB RT progressed, with the trend continuing six months after RT completion.
This study demonstrated the changes that occur in myocardial tissue as measured by Echocardiography strain imaging in patients undergoing RT for left sided breast cancer. As an entire group, LVGLS worsened compared to baseline. However, DIBH significantly reduced LVGLS measurements as compared with patients treated in FB, confirming the protective benefit of DIBH.