How do you reconcile data from the PATINA trial and DESTINY-Breast09 with respect to CDK4/6 inhibitor maintenance in metastatic ER+ HER2+ breast cancer?

We don't have data on using T-DXd with palbociclib concurrently, but the data from DB09 and PATINA does lead to questions about the optimal 1st line approach in ER+HER2+ metastatic disease. DB09 allowed for concurrent endocrine therapy with T-DXd + P, and the ADC was continued until intolerance or p...

I think of PATINA and DESTINY-Breast09 as addressing different treatment phases rather than offering competing strategies. PATINA clearly supports the ongoing role of estrogen receptor signaling in ER-positive, HER2-positive metastatic disease and shows that adding a CDK4/6 inhibitor to endocrine th...

I am not adding CDK4/6 inhibitors to T-DXd outside of a clinical trial. In patients with ER+/HER2+ MBC who received 1L THP, I am routinely offering HP/palbociclib/ET in the maintenance setting. For patients with ER+/HER2+ MBC who received 1L T-DXd/P, it is unknown what the outcomes will be with some...

This is a difficult decision as both trials suggest substantial benefit. It would depend in part on the DFI from the last adjuvant HP. If short, then endocrine therapy was not very effective, and HP is unlikely to be particularly useful, therefore T-DXd is probably a better approach.