OBJECTIVES: To evaluate the effectiveness of palbociclib plus letrozole or fulvestrant in HR+/HER2- post-menopausal advanced or metastatic breast cancer patients.

METHODS: The effectiveness analysis of palbociclib plus letrozole/fulvestrant was based on a partitioned survival model, using data from PALOMA-1, PALOMA-2 and PALOMA-3 clinical trials. A combined analysis with KM data and parametric projections was used to estimate progression-free survival (PFS) and overall survival (OS) curves, defining patients’ distribution between the health states pre-progression, progressed disease and death. EQ-5D-3L utility weights were derived from EQ-5D-3L questionnaires from PALOMA-2 and PALOMA-3 for PFS and post-progression in active treatment and from the literature for post-progression in Best Supportive Care (BSC). Health outcomes were estimated for a lifetime horizon. Deterministic and probabilistic sensitivity analyses were conducted to assess the robustness of results.

RESULTS: Adding palbociclib to letrozole in patients without prior treatment for advanced disease increases average life expectancy by 0.41 life-years (LY) enabling a gain of 0.57 quality adjusted life years (QALY). Adding palbociclib to fulvestrant in patients who progressed or relapsed during previous endocrine therapy increases average life expectancy by 0.76 LY enabling a gain of 0.52 QALY. In both cases most gains of palbociclib are due to increased PFS. Deterministic sensitivity analyses show that results are robust to most scenarios but sensitive to parametric extrapolation of both PFS and OS and utility weights.

CONCLUSIONS:The treatment with palbociclib plus letrozole/fulvestrant showed a relevant incremental effectiveness both in terms of LY and QALY in the treatment of HR+/HER2- locally advanced or metastatic breast cancer in Portugal.