Subclinical left ventricle impairment following breast cancer radiotherapy: Is there an association between segmental doses and segmental strain dysfunction?

Background: Cardiotoxicity following breast cancer radiotherapy (RT) represents one of the most redoubtable toxicities. The Global longitudinal strain measurement (GLS) based on 2D speckle tracking imaging (STI) allows detection of left ventricular (LV) dysfunction at a subclinical stage. The aim of this prospective study was to detect patients at risk of cardiotoxicity using echocardiographic parameters and to determine the association between segmental RT doses and early cardiac toxicity.

Material and methods: The STI was performed prior to RT and at 3, 6 and 12 months after. The association between subclinical LV dysfunction, defined as a reduction of GLS more than 10% from the initial value, radiation doses to different LV segments and non-radiation factors were performed based on multivariate analyses.

Results: From June 2017 to August 2018, a total of 103 female patients were included. Sixty patients had left sided RT. Seven patients (7.8%) developed a GSL impairment. The segmental alterations predominated in the anteroseptal and apical LV segments. The mean Dmean in altered segments was significantly higher than in non-altered segments (6.7 ± 8.8Gy-7.8 ± 8.9Gy vs 4.9 ± 7.9-5.4 ± 8.2Gy; p < 0.05). Age > 55 years and obesity were important confounding factors that should be considered during radiotherapy planning.

Conclusion: The results of our study show that radiation dose is correlated with the subclinical LV segments' alteration. Global heart delineation seems to be insufficient during the breast radiotherapy planning. Segmental delineation of the LV may be an interesting alternative to limit segmental doses and to reduce the risk of subclinical alterations. A mean dose of 5Gy could be proposed in exposed heart segment.