ESMO Congress 2026

The standing of T-DXd, a HER2-directed ADC, in high-risk HER2-positive early breast cancer rests on the published phase 3 DESTINY-Breast05: this open-label, international, randomized trial enrolled 1635 patients with residual invasive disease after neoadjuvant therapy (node-positive at surgery or inoperable at diagnosis), randomized 1:1 to T-DXd (5.4 mg/kg) versus the standard of care T-DM1 (3.6 mg/kg), with invasive disease-free survival as the primary endpoint and a median follow-up of approximately 30 months ^[1]; synthesized evidence reports an IDFS HR = 0.47, establishing T-DXd as a new standard in high-risk HER2+ early disease ^[2]. Its postneoadjuvant indication has received FDA approval ^[5][6], and Canada's 2025 HER2+ consensus update accordingly adjusted the placement of ADCs across early and metastatic settings ^[4].

What was reported at ESMO 2026, in a Rapid Oral session on early-stage breast cancer, was the patient-reported outcomes (PROs) from DESTINY-Breast05: in patients with high-risk HER2-positive early breast cancer and residual invasive disease, health-related quality of life was largely maintained in both the T-DXd and T-DM1 arms; by domain, the T-DXd arm showed a longer time to deterioration in pain and arm symptoms compared with T-DM1, while another post noted a tendency toward a longer time to social-functioning quality-of-life deterioration with T-DM1. The posts disclose no instrument, magnitude of score changes, or any specific values.

The step forward: with the efficacy evidence of DESTINY-Breast05 (primary endpoint IDFS and IDFS HR = 0.47) ^[1][2] and its approvals ^[5][6] already positioning T-DXd as the standard post-neoadjuvant choice, these PRO data add the patient perspective to that standard — overall quality-of-life experience was similar between the two drugs, with the T-DXd arm showing a longer time to deterioration in pain and arm symptoms and a tendency favoring T-DM1 in social functioning — providing a quality-of-life reference for shared decision-making in high-risk patients.

Limitations: the posts are qualitative only; the PRO instrument type, definition of deterioration, baseline completion rates, and statistical testing values are undisclosed pending full publication; and the phase 3 trial was open-label ^[1] with patient self-assessment, so interpretation should remain cautious.