First-line therapy with palbociclib in patients with advanced HR+/HER2− breast cancer: The real-life study PALBOSPAIN

Abstract Purpose To evaluate the efficacy and safety of first-line therapy with palbociclib in a Spanish cohort treated after palbociclib approval. Methods PALBOSPAIN is an observational, retrospective, multicenter study evaluating real-world patterns and outcomes with 1 L palbociclib in men and women (any menopausal status) with advanced HR + /HER2– BC diagnosed between November 2017 and November 2019. The primary endpoint was real-world progression-free survival (rw-PFS). Secondary endpoints included overall survival (OS), the real-world response rate (rw-RR), the clinical benefit rate, palbociclib dose reduction, and safety. Results A total of 762 patients were included. The median rw-PFS and OS were 24 months (95% CI 21–27) and 42 months (40-not estimable NE) in the whole population, respectively. By cohort, the median rw-PFS and OS were as follows: 28 (95% CI 23–39) and 44 (95% CI 38-NE) months in patients with de novo metastatic disease, 13 (95% CI 11–17) and 36 months (95% CI 31–41) in patients who experienced relapse 12 months after the end of ET. rw-PFS and OS were longer in patients with oligometastasis and only one metastatic site and those with non-visceral disease. The most frequent hematologic toxicity was neutropenia (72%; grade ≥ 3: 52.5%), and the most common non-hematologic adverse event was asthenia (38%). Conclusion These findings, consistent with those from clinical trials, support use of palbociclib plus ET as 1 L for advanced BC in the real-world setting, including pre-menopausal women and men. Trial registration number NCT04874025 (PALBOSPAIN). Date of registration: 04/30/2021 retrospectively registered.