Ki67 and PR to predict sensitivity of palbociclib: A real-world study.

e13032 Background: Palbociclib combined with endocrine therapy are approved as a front-line treatment for hormone receptor (HR)-positive, HER2-negative advanced breast cancer (ABC). A key challenge remains to uncover biomarkers to identify those patients who may benefit from palbociclib treatment. Methods: We retrospectively analyzed the values of Ki67 and progesterone receptor (PR), detected by immunohistochemistry, in 81 ABC patients with palbociclib and hormone therapy treatment, and evaluated the impact on progression-free survival (PFS). Results: In total population, women with Ki67≥14% had marginal significant shorter PFS than those with Ki67<14%. Patients with Ki67≥30% had significant shorter PFS than those with Ki67<30% ( P=0.048). While PR≥ 20% was associated with longer PFS. And what’s more, the change trend of Ki67 or PR from primary tissue to metastatic lesions was related to PFS. In regard with hormone therapy subgroup, there were significant association between Ki67 and PR levels and PFS in aromatase inhibitors (AIs) subgroup. Patients with Ki67≥14% or Ki67≥ 30% had shorter PFS than those with Ki67<14% or Ki67<30%, respectively ( P=0.024, P <0.001). Additionally, the change trend of Ki67 or PR from primary tissue to metastatic lesions was related to PFS. When both Ki67 and PR are considered, there were significant differences between different cohort. Compared with those with Ki67≥14% and PR <20%, patients with Ki67<14% and PR≥20% had significant longer PFS. In addition, patients with Ki67<30% and PR≥20% had significant longer PFS than those with Ki67≥30% and PR<20%. Besides, in AIs cohort, patients with Ki67<14% and PR≥20% had significant longer PFS than those with Ki67≥14% and PR <20%. Women with Ki67<30% and PR≥20% had significant longer PFS than those with Ki67≥30% and PR<20%. Conclusions: The present study indicates that both Ki67 and PR have a greater impact on palbociclib and hormone therapy and may help selecting a more effective partner of palbociclib.