Induction Therapy of PTX+BV Followed by Atezolizumab+Nab-PTX for PD-L1+ TNBC

The objective of this research is to evaluate the efficacy of the treatment strategy to administer atezolizumab + nab-PTX following 2 cycles of induction therapy with PTX + bevacizumab (induction treatment strategy) in PD-L1-positive mTNBC in comparison with the standard atezolizumab + nab-PTX therapy in a rondomized phase II design. It is hypothesized in this research that in patients with PD-L1-positive mTNBC, 2 cycles of PTX+ bevacizumab induction therapy induce early response and an immune microenvironment conducive to the benefits of immunotherapy, and improve progression-free survival as compared with the standard treatment with atezolizumab + nab-PTX therapy (standard treatment group). The primary objective of this research is to investigate this hypothesis. A key secondary objective is to compare the 2-year PFS rate between the induction therapy group and the standard treatment group in order to assess the long-term effect of the induction treatment strategy. Furthermore, in patients in the induction therapy group who are not assessed as PD in the first imaging assessment, the 2-year PFS rate will be compared to the reference value expected in a historical control to examine the benefits of the induction therapy. Other secondary objectives are to compare the response rate and the disease control rate as efficacy endpoints and to evaluate the effect of the induction treatment strategy on early PD. Overall survival (OS) will also be compared. In addition, with the aim of exploring the mechanism by which the induction treatment strategy contributes to enhancement of the effect of the standard treatment with atezolizumab + nab-PTX therapy, the immune status in the tumor microenvironment and peripheral blood will be evaluated, and its relationship with antitumor effects will be investigated. For evaluation of efficacy and safety in the induction therapy group, 2 cycles of induction therapy + immunochemotherapy will be evaluated as a series of treatments.