Effect of adjuvant trastuzumab for HER2 positive breast cancer combined with radiation therapy and anthracyclines on left ventricular function

Abstract Funding Acknowledgements Type of funding sources: None. Background Although trastuzumab has benefits in treatment of HER2 positive breast cancer, its use is associated with an increased risk of cardiotoxicity. Purpose To assess the effect of adjuvant trastuzumab in HER2 positive breast cancer pts, in addition to prior radiation and antracyclines therapy, on left ventricular function. Methods Fifty HER2 positive female breast cancer patients (mean age, 59.57±9.6 years) were enrolled in the study. In all patients (pts) left ventricular left ventricular ejection fraction-LVEF(%) and left ventricular mass – LVM (g) were assesed at the beginning and after the therapy with trastuzumab. All pts were on sequential therapy with anthracyclines (IV cycles) within the FAC regimen (fluorouracil 500 mg/m2, doxorubicin 50 mg/m2, cyclophosphamide 500 mg/m2) on day 21, and after that followed with trastuzumab (6 mg/kg of body weight on day 21) for the period of one year. The pts are divided in two groups: the group of patients (N=32 pts) who had prior radiation therapy (25 daily sessions of 2 Gy dose each, up to the total dose of 50 Gy) and group without radiation therapy (N=18). Results After completion of trastuzumab therapy pts who underwent radiation therapy, reduced LVEF by 2.24 % (from 66.58 ± 5.36 % to 64.34±7.34 %; p=0.048) and increased LVM by 17.95 g (from 160.38 ± 46.21 g to 178.33 ± 53.14 g; p=0.018) . The group of pts without radiation therapy, reduced LVEF by 0,72 % (from 63.33±7.60 % to 62.61±6.92 %; p=0.979) and increased LVM 23.34 g (from 141.98±35.82 g to 165.32±47.45 g; p=0.062). Conclusion The results of the study showed that the decline of LVEF and increase of LVM after completion of adjuvant trastuzumab therapy for HER2 positive breast cancer iz related with previous prior radiation administration. The pts with radiation had greater reduction of LVEF and increase of LVM than those without radiation.