Cardiological Safety of 5-Fraction Whole Breast Irradiation

Abstract

Our study aims to assess heart toxic effect using a reliable cardiac assessment with standard and 3-dimensional (3D) echocardiography and left ventricular (LV) global longitudinal strain (GLS) in patients receiving a 5-fraction (total dose 26 Gy) postoperative radiation therapy (RT) for breast cancer (BC). SAFE-FORWARD is an observational prospective cohort study (NCT04842409). Inclusion criteria were: (1) patients with invasive BC receiving ultra-hypofractionated whole breast irradiation (WBI) (26 Gy in 5 fractions) after breast conserving surgery (BCS) (2) without cardiovascular comorbidity and (3) previous thoracic irradiation. All enrolled patients are prospectively monitored for 12 months, receiving a complex cardiological assessment before RT start (baseline), and at 2-, 6-, and 12-month after RT end of treatment. Both acute and early-late toxicity are evaluated according to CTCAE (v.5) scales. The primary endpoint is defined as detection of any subclinical impairment in myocardial function and deformation (decrease ≥10%) measured with standard and 3D echocardiography and LV GLS. Overall, 40 women (median age 66 years; range, 48-84) were enrolled in the study. We analyzed patients who had completed the cardiological assessment at 12 months. Baseline patient's characteristics are summarized in Table 1. All patients received ultra-hypofractionated WBI (26 Gy in 5 fractions), 25 patients also received adjuvant endocrine therapy. GLS worsened 4% or less, both for the left- and right-side treated breast, and remained in normal range for all the time points. The only exception was for RVGLS at 6 months for right-sided treatment where it reached a borderline value (-17.4±4.9 SE). 3D-LVEF remains stable during observation, both for the left- and right-side treated breast CONCLUSION: The 5-fraction schedule after BCS is well tolerated and the intensive 1-year cardiological monitoring showed no significant differences overtime in cardiac functioning. DIBH, deep inspiration breath hold; AI, aromatase inhibitors; BCCT, Breast Cancer Conservation Treatment.