Treatment discontinuation, patient-reported toxicities and quality-of-life by age following trastuzumab emtansine or paclitaxel/trastuzumab (ATEMPT).

In the ATEMPT trial, adjuvant trastuzumab emtansine (T-DM1) compared to paclitaxel plus trastuzumab (TH) for stage I HER2-positive breast cancer improved patient-reported outcomes (PROs), while maintaining excellent disease outcomes. We report treatment discontinuation and use multivariable models to compare, patient-reported toxicity and quality-of-life (QOL) by age (≤50, >50) and treatment arm at 18 months post-enrollment among 366 eligible participants randomized in a 3:1 ratio to T-DM1 or TH. T-DM1 discontinuation was higher among women >50 vs. ≤50 (23% vs. 9%, p = 0.003, Fisher's Exact test) with 4%, 8%, and 17% of older patients discontinuing treatment by 3, 6, and 9 months, respectively. Superior QOL with T-DM1 vs. TH was observed among women ≤50 with estimated mean difference of 6.48 (95% confidence interval (CI) 0.51-12.46) and driven by better social/family well-being and breast cancer-specific sub-scores. Among women >50, T-DM1 was associated with superior physical well-being and less activity impairment, with no differences in global QOL. Older women had decreased neuropathy with T-DM1 vs. TH. De-escalated treatment regimens for HER2 positive breast cancer may have age-varying impact on treatment tolerance, toxicities and subsequent QOL, which should be considered when selecting therapy options.Clinical Trial Registration: ClinicalTrials.gov, NCT01853748.