Breast Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_12_3436 - Changes in Cardiac MRI Derived Left Ventricular Segmental Strain in Left Sided Breast Cancer Patients Treated With Tangential Radioation Therapy Alone Correlated With Dose

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Changes in Cardiac MRI Derived Left Ventricular Segmental Strain in Left Sided Breast Cancer Patients Treated With Tangential Radioation Therapy Alone Correlated With Dose
S. C. Tang1,2, E. S. Koh1,3, R. Rai1,3, J. Otton3, A. Herschtal4, D. Tran5, G. Delaney2, L. Holloway6, L. Thomas7, B. Schmitt8, G. Liney1, and S. Ananthapadmanachan9; 1Liverpool Cancer Therapy Centre, Liverpool, Australia, 2Ingham Institute of Applied Medical Research, Liverpool, Australia, 3University of New South Wales, Sydney, Australia, 4Centre for Biostatistics and Clinical Trials, Peter MacCallum Cancer Centre, Victoria, Australia, 5Department of Cardiology Liverpool Hospital, Liverpool, Australia, 6Institute of Medical Physics, School of Physics, University of Sydney, Sydney, Australia, 7University of Sydney, Sydney, Australia, 8Siemens Healthcare Pty Ltd, Sydney, Australia, 9Department of Cardiology, Liverpool Hospital, Liverpool, Australia

Purpose/Objective(s): Reduction in left ventricular global and segmental myocardial strain following tangential radiotherapy (RT) for left sided breast cancer treatment has been demonstrated using advanced echocardiographic techniques. This study aimed to determine if cardiac MRI (CMR), a more sensitive and precise imaging modality, could detect similar changes in segmental myocardial strain as per the American Heart Association(AHA) 16 segment model of the left ventricle in left sided breast cancer patients, and correlate this to RT dose.

Materials/Methods: For 21 patients receiving left-sided breast RT, two serial CMR scans were obtained; immediately prior, and 4-6 weeks following RT. Single breath-hold Steady-State Free Precession (SSFP) Cine 2, 3, 4 chamber and short axis views were acquired, and using cvi42 tissue tracking software, two independent readings of 2D and 3D strain values were obtained, with the average being used for analysis. A linear mixed effects model was used to account for potential clustering of values between patients and segments. Multiple RT dosimetric values (including mean, max, V25) of each segment were calculated and their relationship with delta 2D/3D strain values explored.

Results: Median age was 59 years (range 38-76 years). Comprehensive nodal treatment using modified wide tangents using a deep inspiration breath hold technique (n=1) and the remainder received tangential breast radiation alone (n=20). No patient received chemotherapy. Two patients received 50Gy in 25 fractions, with 19/21 receiving 42.4Gy in 16 fractions. Median mean heart dose was 2.6Gy (1.5-3.9Gy). No difference was found between any pre and post RT strain parameters. These results are summarised in the table below.
Strain Parameter Pre-RT Mean Post-RT Mean Difference 95% CI
Radial 2D (Short Axis) 54.59 50.23 -3.43 [-8.8, 1.9]
Circumference 2D (Short Axis) -23.11 -22.15 0.73 [-0.51, 2.0]
Radial 2D (Long Axis) 48.56 47.46 0.07 [-3.7, 3.8]
Longitudinal 2D (Long Axis) -22.45 -22.27 -0.08 [-0.80, 0.63]
Radial 3D 40.77 37.85 -2.17 [-7.4, 3.1]
Circumference 3D -20.05 -19.20 0.72 [-0.62, 2.1]
Longitudinal 3D -19.49 -18.92 0.47 [-0.79, 1.7]
Note the calculated differences are modelled quantities taking into account patients as a random effect and missing data. Therefore values in Difference column are not equal to pre RT mean minus post RT mean. When correlated with several radiation measures, there were no significant relationships between any radiation parameters and change in serial strain.

Conclusion: No differences in left ventricular segmental strain were detected using CMR 4-6 weeks following left-sided breast radiotherapy, nor was there a clear relationship between RT dose and delta strain. Changes below the threshold of CMR detection given the lower temporal scanning resolution of CMR cannot be excluded. Longer term follow-up of this cohort will help determine if more delayed effects of radiation on LV function become manifest.

Author Disclosure: S.C. Tang: Research Grant; RANZCR 2016 Research Grant. E. Koh: None. J. Otton: None. A. Herschtal: None. D. Tran: None. G. Delaney: None. L. Holloway: None. L. Thomas: None. S. Ananthapadmanachan: None.

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