A recent real-world study conducted in Northwest China has affirmed the efficacy and tolerability of Palbociclib in combination with endocrine therapy (ET) for patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC). The study, published in BMC Cancer, provides valuable data on the use of Palbociclib in a real-world setting, reflecting the challenges and patient characteristics often underrepresented in clinical trials.
The research, led by investigators in China, retrospectively analyzed data from MBC patients treated with Palbociclib plus ET. The primary objective was to evaluate the real-world effectiveness of this treatment regimen in a population with potentially different characteristics and healthcare access compared to those in pivotal clinical trials like PALOMA-2 and PALOMA-3.
Progression-Free Survival and Overall Response
The study found that patients receiving Palbociclib plus ET as first-line treatment had a median progression-free survival (PFS) of 12.2 months, consistent with other retrospective studies. Notably, the data strongly supported earlier initiation of Palbociclib, with median PFS of 14.2, 10.6, and 8.7 months in the first-, second-, and later-line settings, respectively. While the overall response rate (ORR) was 21.8%, the disease control rate (DCR) reached 90.5%, indicating a substantial proportion of patients experienced disease stabilization.
Impact of Prior Therapies and Patient Characteristics
The study also identified factors associated with patient outcomes. Patients with no prior chemotherapy for MBC had a better PFS compared to those who had received prior chemotherapy (HR = 0.55; P = 0.004). Similarly, patients with no prior endocrine therapy for MBC also experienced improved PFS (HR = 0.62; P = 0.023). These findings suggest that prior treatments can influence the effectiveness of Palbociclib-based therapy.
Furthermore, the study revealed that low progesterone receptor (PgR) expression negatively impacted PFS. This observation aligns with some previous studies suggesting a potential association between PgR levels and response to CDK4/6 inhibitors.
Comparison with Clinical Trials
Compared to the PALOMA trials, the real-world study included a higher proportion of patients with characteristics often excluded from clinical trials, such as those with poor performance status, visceral metastasis, and prior chemotherapy. These differences may explain some of the variations in outcomes observed between the real-world study and the clinical trials.
For instance, the ORR in the first-line setting was lower in the real-world study (27%) compared to the PALOMA-2 trial (42%). This difference may be attributed to the inclusion of more premenopausal women and patients with prior (neo)adjuvant chemotherapy in the real-world cohort.
Implications for Clinical Practice
Despite these differences, the study provides valuable insights into the use of Palbociclib in a real-world setting. The findings suggest that Palbociclib-based therapy is a viable treatment option for MBC patients in China, even in later lines of therapy. However, the study also highlights the importance of considering patient characteristics and prior treatments when making treatment decisions.
Limitations
The authors acknowledge several limitations to the study, including the potential for selection bias due to the retrospective design and the lack of uniform imaging evaluation. Additionally, the follow-up period was relatively short, and further analysis will be needed after a longer period of follow-up.
Despite these limitations, this study represents the largest Chinese cohort treated with Palbociclib in an unselected real-world setting, providing a considerable amount of data in support of the efficacy and tolerability of Palbociclib.
