Real-world treatment patterns and sequencing in patients with advanced / metastatic HR+/HER2- breast cancer in Europe and the United States.

[BACKGROUND] For patients with advanced breast cancer (ABC), standard-of-care (SOC) treatment in first line (1L) with CDK4/6 inhibitors (CDK4/6i) in combination with endocrine therapy (ET) is well established. However, data on treatment patterns in second line (2L), where the treatment landscape is evolving, are lacking. This large real-world study investigated treatment sequencing from 1L to 2L in patients with HR+/HER2- ABC in the post-CDK4/6i era.

[METHODS] Data leveraged the Adelphi ABC Disease Specific Programme (DSP)™, a cross-sectional survey conducted in Europe and the United States between July 2022 and March 2023. Physicians provided data for consecutively consulting patients, including current and historic clinical status, treatment sequencing and biomarker testing history. All analyses were descriptive.

[RESULTS] Data for 767 patients with HR+/HER2- ABC receiving 2L treatment at data collection were analyzed. In 2L, 31.6% received chemotherapy-based regimens, 17.7% received ET monotherapy, 21.5% received CDK4/6i + ET, and 26.3% received a targeted therapy (mTOR/PARP/PI3K inhibitors). Of those receiving 2L, 58% previously received a CDK4/6i regimen in 1L, in line with treatment guidance, while 21% received chemotherapy. Use of targeted therapies in 2L was driven by biomarker testing. Country/region-specific variation in biomarker testing and treatments were likely due to differences in local guidance and practice.

[CONCLUSION] This study provides insights into treatment sequencing in patients with HR+/HER2- ABC who progress to 2L in the post-CDK4/6i era. For patients without targetable mutations, there is no clear SOC at 2L and treatment options are limited. New treatments may further shape this developing landscape.