Researchers have conducted a multi-country Iberance Real World Insights (IRIS) study, which aims to provide country-specific real-world data that can be used to complement clinical trial data, with a larger and more diverse sample of patients receiving Palbociclib as a treatment for advanced breast cancer. The researchers hope that the IRIS study will address the evidence gap between clinical trials and the real-world clinical setting.
Advanced breast cancer and palbociclib
In Canada alone, it is estimated that there were around 27,000 breast cancer diagnoses and 5,100 deaths in 2020. Human receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2–) breast cancer is one of the most common subtypes in Canada. The complexity of breast cancer subtypes and their classification, as well as the emergence of resistance to endocrine agents, has led to the development of targeted treatments to improve health outcomes in patients with advanced breast cancer (ABC) and metastatic breast cancer (MBC).
Palbociclib was the first selective cyclin-dependent kinase (CDK) 4/6 inhibitor that was approved for use in Canada. It is used in combination with letrozole, for the treatment of post-menopausal women with estrogen receptor-positive (ER+) HER2– ABC. It has since been used in combination with fulvestrant for the treatment of women with HR+/HER2–, whose disease has progressed after previous endocrine therapy.
Although extensive clinical trial data is available for palbociclib, evidence for its use in real-world patients is still emerging. Moreover, the 5-year survival rate for patients with stage 4 breast cancer has been estimated at around 22%. Therefore, further research needs to be done to improve survival outcomes for these patients.
The IRIS study
The multi-country IRIS study was carried out with the aim to describe demographic, clinical characteristics, treatments and outcome data, including progression-free survival rates (PFRs) and survival rates (SRs), for patients who received palbociclib combinations in the real-world setting. Overall, the study worked to collect data from over 2,900 palbociclib-treated patients, across 13 countries in America, Europe and Asia. The researchers hoped that this study would provide country specific real-world data that could be used to complement clinical trial data, through assessment of a larger and more diverse sample. This could then be used to address the evidence gap between clinical trials and the real-world setting.
This article focused on findings from the Canadian cohort of patients. Previous articles have published the results from the US, German and Argentinian cohorts. The review included women with HR+/HER2− ABC and MBC receiving palbociclib and fulvestrant, or palbociclib and letrozole in Canada. The data was collected by reviewing medical records for up to 14 patients from each participating physician, abstracting demographic and clinical characteristics, treatment patterns and clinical outcomes. PFRs and SRs at 16, 12, 18 and 24 months were estimated using Kaplan–Meier analysis, a non-parametric statistic used to estimate the survival function from lifetime data.
As the IRIS study only included physicians that were willing to share patient data, selection biases had to be considered. To minimize the effect of this, physicians were asked to select consecutive patients in line with the index date.
Real-world results of Palbociclib treatment
Overall, thirty-three physicians were involved in the study, and the medical reviews for 247 patients were reviewed. This included 214 patients being treated with palbociclib and letrozole and 33 who were treated with palbociclib and fulvestrant. It was found that 78.2% of patients receiving palbociclib + letrozole remained progression-free after 18 months. Meanwhile, 91.0% of patients receiving palbociclib + fulvestrant were progression-free after 6 months. Furthermore, the SR at 18 months was 93.0% for patients receiving palbociclib + letrozole and 100.0% for palbociclib + fulvestrant treatment. Although differences in patient characteristics limit the level to which we can compare the outcomes of the IRIS study and clinical trial results, responses and survival data from IRIS complement the efficacy data for palbociclib combinations observed in trial results.
The IRIS study provided information regarded real-world treatment patterns and clinical outcomes associated with palbociclib in combination with letrozole or fulvestrant for patients with ABC and MBC in Canada. The results from this study complemented the findings reported from clinical trials. This suggests that the drug is well tolerated in the real-world setting. Further work is needed to deliver mature outcome data beyond 12/24 months in this setting, to further validate this study
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