Abstract 239P
Background
The majority of metastatic invasive lobular carcinoma (mILC) are hormone receptor (HR)-positive, HER2-negative and initially responds well to endocrine therapy (ET) in combination with targeted therapies (TT). However, once ET-refractory, data on the efficacy of single-agent chemotherapy regimens are limited. We investigated the efficacy of capecitabine (CAP) versus taxanes (TAX) in ET-refractory HR+ HER2- mILC patients.
Methods
In an observational investigation using data from the MD Anderson breast cancer prospectively collected electronic database, we searched for patients with a diagnosis of HR+ HER2- mILC who were exposed to prior lines of ET (either alone or in combination with TT) and who received first-line chemotherapy in the metastatic setting (ET-refractory mILC). We collected data on clinicopathological features, chemotherapy type, treatment duration and survival status. The Kaplan-Meier product-limit method was used to compare progression-free survival (PFS) and overall survival (OS) between the two different groups. Backward model selection was used to find the final multivariate Cox model for PFS and OS.
Results
We reviewed 269 subjects: 173 (65%) received CAP and 96 (35%) received TAX. Patients characteristics were well balanced between the 2 groups: median age 52, 80% White, 61% had non-visceral disease, and 47% received only one prior ET. Subjects who received CAP had statistically significant better median PFS compared to TAX (8.8 vs 5.0 months, HR 0.63, P <0.0001). There was no statistically significant difference in OS between the two groups (42.7 vs 36.6 months in CAP vs TAX respectively, HR 0.85, P = 0.214). Multivariate Cox analysis for PFS showed that subjects who received CAP, had fewer metastatic sites, and were exposed to more lines of ET had better outcomes. Multivariate Cox analysis for OS showed that subjects who identified as Asian or Hispanic, and subjects exposed to more lines of ET had better outcomes, whereas subjects who identified as Black had worse outcomes compared to those who identified as White (HR 2.5; P = 0.0016).
Conclusions
The analysis suggest that ET-refractory mILC subjects treated with CAP were associated with longer PFS but not OS compared to those treated with TAX.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
J. Mouabbi: Financial Interests, Personal, Invited Speaker: BostonGene; Financial Interests, Personal, Advisory Board: Cardinal Health. D. Tripathy: Financial Interests, Personal, Advisory Board: Novartis, Pfizer, Exact Sciences, GlaxoSmithKline, AstraZeneca. R.M. Layman: Financial Interests, Personal, Funding: Pfizer, Eli Lilly, Novartis, GlaxoSmithKline, Puma, Zentalis, Celcuity. All other authors have declared no conflicts of interest.