What criteria would you use to decide between trastuzumab-deruxtecan and sacituzumab govitecan in HER2 low metastatic TNBC given T-DXd approval in HER2 low breast cancer?

There are currently unfortunately no biomarkers to select participants for antibody drug conjugate therapies, including sacituzumab and trastuzumab deruxtecan for HER2 low metastatic TNBC.

The studies evaluating sacituzumab govitecan and trastuzumab deruxtecan had different I/E criteria, including with regard to prior lines of therapy.

1. The ASCENT trial for sacituzumab was a dedicated TNBC trial, required progression on 2 prior lines of therapy in the metastatic setting, and included 468 patients...

I think this question can now be broadened out beyond TNBC to ER+Her2- metastatic disease. While in TNBC the evidence supports (I think) using sacituzumab prior to leaning on TDXd, I would personally argue for using TDXd prior to trying sacituzumab in HR+ disease based on response rates and benefit seen in the respective trials.

Given that both antibodies use a similar drug conjugate, I will be interested to see what I anticipate will be data on response rates and duration of response as these d...