How would you treat frontline metastatic ER+HER2- breast cancer with activating PI3K mutations?

Outside of a clinical trial, I would still treat patients with HR+/HER2-, PIK3CA mutant, metastatic breast cancer with hormone therapy + CDK 4/6 inhibitor. At this moment, we are still awaiting approval of alpelisib. In the phase 3 SOLAR-1 trial, 341 patients with PIK3CA mutant tumors were randomized to fulvestrant +/- alpelisib. Of these, 177 were treated "first line." The PFS in the alpelsilb arm was 11.0 vs. 6.8 in the placebo arm (HR: 0.71). These included patients who progressed < 1 year from (neo)adjuvant endocrine therapy (endocrine resistant) and those > 1 year (endocrine sensitive - later excluded). The numbers are very small and hypothesis generating - but the HR for the endocrine sensitive was 0.87 (n=39) and 0.69 for endocrine r...