Overall survival of palbociclib plus endocrine therapy in Japanese patients with HR+/HER2- advanced breast cancer in the first-or second-line setting: a multicenter observational study (P-BRIDGE study).

Background: Recently, we reported the real-world effectiveness of palbociclib plus endocrine therapy (ET) in HR+/HER2- advanced breast cancer (ABC) in Japan (NCT05399329). However, median overall survival (OS) was not reached because of limited follow-up (36 months). Here, we present follow-up data from this study, including real-world clinical outcomes and treatment patterns.

Methods: The P-BRIDGE study was a multi-center, observational study evaluating the real-world effectiveness and treatment patterns of patients diagnosed with HR+/HER2- ABC who received palbociclib plus ET in first (1L) or second line (2L) in Japan. The primary endpoint was real-world progression-free survival (rwPFS); secondary endpoints included OS and chemotherapy-free survival (CFS).

Results: Of the 693 eligible patients, 426 and 267 patients received palbociclib with ET as 1L and 2L treatment, respectively. After a median follow-up of 48.1 months, the median rwPFS (95% CI) was 26.2 months (21.4-30.4) for 1L and 14.9 months (11.7-18.3) for 2L, respectively. Median OS (95% CI) was 68.2 months (60.8-NE) for 1L and 50.7 months (42.2-57.2) for 2L, respectively. OS analysis was also performed in the following subgroups: TFI < 12 months/TFI ≥ 12months/de novo metastatic median OS was 56.3 months (43.9-68.2), NR (NE-NE), NR (56.3-NE), visceral metastasis was 65.0 months (56.3-NE), liver metastasis was 46.4 months (37.2-NE), and bone only metastasis was NR (57.8-NE) in 1L, respectively.

Conclusions: The updated results from this study further confirm the real-world effectiveness of palbociclib plus ET in routine clinical practice in Japan. More than 5 years of median OS in 1L was observed, supporting the use of palbociclib plus ET as 1L standard of care for HR+/HER2- ABC.