The Study: As a reminder, it was a UK trial that randomized over 4K women receiving chemo to 6 versus 12 months of trastuzumab. It was designed to prove the non-inferiority of disease-free survival (DFS) at 4 years (within an absolute difference of 3%). Close to 60% of women had N0 disease and another 25-30% had 1-3 involved nodes. Most (69%) also had ER(+) tumors. Final results are here, and at 4 years the absolute difference in DFS was 0.4% (89.4 versus 89.8%), which believe it or not achieved non-inferiority. The secondary endpoint of overall survival was also non-inferior. 12 months of trastuzumab resulted in a 5% absolute increase in grade 3+ toxicity that were mainly seen in the >6 months time frame. Roughly 90% of chemo regimens included an anthracycline, and heterogeneous outcomes were suggested among the subset receiving taxanes. So with TCH +/- P being a more common contemporary regimen, some question the direct applicability of this trial to non-anthracycline regimens.
Bottom Line: Among women with fairly early-stage and mostly ER(+) HER2(+) breast cancer receiving mostly anthracycline-based chemo, 6 months was non-inferior to 12 months of adjuvant trastuzumab. | Earl, Lancet 2019