Adjuvant Escalation and Long-Term Benefit: Rethinking Sequencing After Early HER2 Exposure

This segment explores how emerging data from the adjuvant and post-neoadjuvant settings are reshaping expectations for treatment sequencing later in metastatic HER2-positive breast cancer. Dr. Bill Gradishar begins by describing this as a rapidly evolving area, driven by the movement of highly active agents into earlier lines of therapy. Historically, the KATHERINE trial established T-DM1 as the standard for patients with residual disease after neoadjuvant treatment, demonstrating improved outcomes regardless of residual disease burden. However, newer data now suggest that T-DXd may be superior to T-DM1 even in this post-surgical context.

These advances raise critical downstream questions. As patients increasingly receive potent antibody–drug conjugates in the adjuvant or neoadjuvant setting, clinicians must reconsider options at the time of metastatic recurrence. Dr. Gradishar notes that whether a drug can be reused may depend heavily on the interval between treatment and relapse. A long disease-free interval may justify reintroduction of T-DXd, whereas early recurrence could prompt a switch to a different mechanism of action, such as a tucatinib-based regimen like HER2CLIMB. He emphasizes that this remains an open question, with multiple new agents and strategies under investigation.

Dr. Jason Mouabbi then contextualizes these decisions through lessons from the 10-year follow-up of the APHINITY trial. Long-term data showed a sustained, though modest, benefit from adding pertuzumab in the adjuvant setting, particularly for node-positive patients. He highlights that traditional “naked” antibodies lack cytotoxic payloads and have limited immune activation, which may constrain their durability later in metastatic sequencing. As the field shifts toward earlier use of ADCs and dual HER2 blockade, Dr. Mouabbi suggests moving away from simply recycling older antibodies. Instead, he points to newer engineered antibodies, enhanced ADCs, and emerging bispecific agents as promising options to deliver more durable benefit. Together, the panel underscores how early treatment intensification is fundamentally redefining long-term sequencing strategies in HER2-positive breast cancer.