Changes in Left Ventricular Function after Radiation Therapy and Trastuzumab: Analysis of North Central Cancer Treatment Group Phase III Trial N9831

Results: At 2‐4 months after RT, the percentage of patients with . = 5% absolute decline from prior to RT in LVEF for left- vs. right-sidedRTwas22/94(23%)vs.30/119(25%)(p=0.76)inarmA,26/97(27%)vs.40/112(36%)(p=0.17)inarmB,and16/74 (22%) vs. 20/80 (25%) (p = 0.62) in arm C. Only 11/576 (2%) of patients had . = 15% absolute decline at this time point (2 leftsided arm A; 5 left- and 4 right-sided arm B). At 10‐14 months after RT, the percentage of patients with . = 5% absolute decline from prior toRT inLVEFfor left- vs.right-sided RTwas17/84 (20%)vs.22/106(21%)(p= 0.93)inarm A, 20/51(39%) vs.15/46 (33%) (p = 0.50) in arm B, and 21/75 (28%) vs. 18/77 (23%) (p = 0.51) in arm C. Only 12/439 (3%) of patients had . = 15% absolute decline at this time point (2 left- and 3 right-sided arm A; 1 left- and 1 right-sided arm B; 3 left- and 2 right-sided arm C). Conclusions: Administration of adjuvant RT with H in early-stage breast cancer patients is not associated with a significant difference in LVEF change between patients receiving left- vs. right-sided RT. The same was observed in the arm without H. Further follow-up is warranted to assess longer-term effects of H and RT.