Survival following adjuvant trastuzumab-based treatment among older patients with HER2-positive early invasive breast cancer: A national population-based cohort study using routine data.

In this national dataset, adjuvant trastuzumab was associated with improvements in survival, with an OS effect size similar to RCT evidence. The effect size was not found to vary by patient age or fitness. Chronological age and fitness alone should not be barriers to receipt of effective adjuvant targeted treatment.