Introduction—Current Treatment Landscape in PD-L1+ Metastatic Triple-Negative Breast Cancer (mTNBC)

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Tiffany A. Traina, MD: Hi everyone. I'm Tiffany Trina, breast medical oncologist at Memorial Sloan Kettering, and it's my privilege to kick us off for this session and set a little bit of groundwork in talking about triple-negative breast cancer, sort of at baseline. As we think about the first-line space for advanced TNBC, it is really critical that we consider PD-L1 status for the tumors here because that has really defined the algorithm and the way in which we approach our treatment recommendations for patients. PD-L1 is expressed in about 40% of tumors that are triple negative, and this has been critically important because it is quite actionable. There have been several studies summarized here in this meta-analysis that have shown that when immune checkpoint inhibitors are added to traditional backbone chemotherapy like taxanes or platinum-based therapy, we see substantial improvements in progression-free survival and overall survival.  

I have to say, my practice has been caring for patients with primarily TNBC for a long time, and cytotoxic therapy in and of itself has been rather disappointing. So, when we had the ability to add a checkpoint inhibitor to that first-line chemo, it was one of the biggest differences we had seen for a long time in taking care of patients with advanced TNBC. Obviously, not perfect, and we still have room for improvement, and that's why we're here this morning to talk about some of the new exciting opportunities for our patients. The other big advantage that we really felt in our practices taking care of women with TNBC was the advent of antibody drug conjugates, and particularly the anti-TROP-2 ADC, sacituzumab govitecan, was a real game-changer for our patients. The ASCENT study looked at sacituzumab compared to chemotherapy in patients who were treated primarily third line and later, but allowed for patients being treated in the second-line setting. Sacituzumab as a single ADC was quite superior to chemotherapy in this population, with improvements in PFS as well as improvements in overall survival. As you can see here, and as we'll hear from our speakers, plenty of other studies have been looking at moving sacituzumab govitecan up earlier than the second-line setting into the first-line setting, even among those high-risk folks who have residual disease after neoadjuvant treatment.