Efficacy of Palbociclib Combinations in Hormone Receptor-Positive Metastatic Breast Cancer Patients After Prior Everolimus Treatment.

PURPOSE

Outcome data on hormone receptor positive (HR), human epidermal growth factor receptor 2 (HER2) nonamplified (HER2) metastatic breast cancer (MBC) treated with palbociclib after treatment with everolimus are lacking. The PALOMA-3 trial, showing benefit of palbociclib plus fulvestrant compared to fulvestrant alone in HRHER2 MBC after progression while receiving endocrine therapy excluded women previously treated with everolimus. The objective of this study was to examine outcomes of HRHER2 MBC with prior exposure to everolimus while receiving palbociclib-based therapy.

PATIENTS AND METHODS

A retrospective, single-institute review was conducted of HRHER2 MBC from January 2014 to November 2016 in patients treated with palbociclib after prior treatment with everolimus. Progression-free survival (PFS) was defined as the time from initiation of palbociclib to the date of progression as determined by the treating physician based on radiologic, biochemical, and/or clinical criteria. Response rates were determined on the basis of available radiologic data. Objective response rate (ORR) was defined as the rate of any complete or partial responses; clinical benefit rate (CBR) was the rate of complete response, partial response, or stable disease for at least 24 weeks.

RESULTS

Twenty-three patients with a mean (range) age of 68 (42-81) years were identified. Kaplan-Meier estimate showed median PFS of 2.9 months (95% confidence interval, 2.1-4.2); ORR was 0 of 23 and CBR was 4 (17.4%) of 23. In the PALOMA-3 trial, median PFS, ORR, and CBR of palbociclib cohort were 9.5 months (95% confidence interval, 9.2-11.0), 19%, and 67%, respectively.

CONCLUSION

There is a limited clinical activity of palbociclib combinations after progression with everolimus combination therapy. Further studies are necessary to confirm these findings.