25 Remedy Patterns and Scientific Outcomes Following Endocrine Resistance Amongst HER2-Low Metastatic Breast Most cancers Sufferers— Retrospective Observational Research

Background

Endocrine remedy (ET) with or with out CDK4/6 inhibitors serves as an preliminary therapy for hormone receptor–optimistic/HER2-low (immunohistochemistry [IHC] 1+ or IHC 2+/in situ hybridization–damaging [ISH]–) metastatic breast most cancers (mBC). Nonetheless, many sufferers progress on ET-based regimens and obtain subsequent chemotherapy (CT). This research examined therapy patterns and outcomes of sufferers with HR+/HER2-low mBC in US group oncology practices after creating endocrine resistance.

Strategies

Oncologists from Cardinal Well being’s Oncology Supplier Prolonged Community supplied information from medical charts of grownup sufferers with HR+/HER2-low mBC who obtained at the very least 2 strains (2L) of systemic remedy, with the primary line (1L) initiated between February 19, 2016, and December 31, 2018. Sufferers who obtained CT after development on their final noticed line of ET-based routine have been analyzed. Affected person traits and therapy historical past have been described, and Kaplan-Meier analyses of therapy outcomes together with physician-reported real-world progression-free survival (rwPFS), time to therapy response (TTR), and time to therapy discontinuation (TTD) have been carried out.

Outcomes

Included have been 150 sufferers with HR+/HER2-low mBC [mean age, 61±11 years; 57.3% White; 32.7% African American] who had CT after ET resistance. The proportion of sufferers who stopped ET after 1L, 2L, and ≥3L of ET have been 23.3% (n = 35), 70.7% (n = 106) and 6.0% (n = 9), respectively. The imply (SD) length of ET-based regimens was 29.7 (13.12) months. Amongst sufferers who stopped ET after 1L (n = 35), most sufferers obtained fulvestrant plus palbociclib (48.6%) in 1L. Amongst those that stopped ET after ≥2L (n = 115), most sufferers obtained letrozole plus palbociclib (57.4%) in 1L and fulvestrant (46.1%) in 2L. The most typical CT utilized was capecitabine (47.0%) adopted by paclitaxel (28.0%).

The median rwPFS on CT was 8.12 months (95% CI, 7.36-9.24), with barely shorter median rwPFS amongst those that stopped ET after 1L at 7.82 months (95% CI, 7.07-9.53) vs 8.19 months (95% CI, 6.97-9.99) in 2L. The median TTD of CT was 7.82 months (95% CI, 7.07-8.61) and TTR was 4.96 months (95% CI, 4.24-5.72), with related estimates noticed between sufferers who stopped ET after 1L and 2L+.

Conclusion

On this small pattern of sufferers with HR+/HER2-low mBC, most sufferers switched to CT after 2L of ET-based regimens. Following ET resistance, sturdiness of CT response was brief and related regardless of variety of prior strains of ET-based regimens. The findings spotlight the unmet want for a simpler therapeutic different to CT after ET for sufferers with HR+/HER2-low mBC.