403P - Breast cancer specific survival (BCSS) in HR+/HER2- metastatic breast cancer (mBC) from 2010 to 2019

Background

Treatment advances, e.g., CDK 4/6 inhibitors (CDK 4/6is) have become standard of care over time in HR+/HER2- mBC in the US since the first approval in 2015. However, whether survival has improved in this patient population post 2015 has not been studied.

Methods

This retrospective study used Surveillance, Epidemiology, and End Results (SEER) registry data to assess BCSS in HR+/HER2- mBC patients from 2010-2019. Kaplan-Meier and Cox Proportional Hazards (CPH) models were used to compare BCSS in two patient cohorts: those diagnosed before (2010-2013 with follow-up [FUP] to 2014), and after (2015-2018 with FUP to 2019) guideline recommendations for CDK 4/6i use.

Results

A total of 11,467 women with de novo HR+/HER2- mBC with a mean age at diagnosis of 62.3 years were included. Unadjusted median BCSS was 39 months for patients diagnosed post 2015 (95% CI: 38-42) and 35 months for patients diagnosed pre 2015 (95% CI: 33-37). After adjusting for age, race & ethnicity, SEER geographic region and site, household income, and marital status, patients diagnosed post 2015 had a 10% reduced risk of BC specific death compared with patients diagnosed pre 2015 (hazard ratio [HR]: 0.90, p<0.01, Table). Table: 403P

Multivariable analysis of predictors of BCSS (CPH)*

*Not all variables included in the model are shown in this table.Significant at **p<0.05 and ***p<0.01Ref: Referent

Conclusions

Using the largest US population-based longitudinal dataset, we observed improvements in BCSS post 2015 in patients with HR+/HER2- mBC. While the limitations of the current analysis prevent attribution to specific treatments, advances such as the introduction of CDK 4/6is in HR+/HER2- mBC may have contributed to population-level improvement in BCSS over time. This is consistent with other RWE studies that have shown an association between CDK4/6i treatment and improved survival.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Pfizer, Inc.

Funding

Pfizer, Inc.

Disclosure

A.M. Brufsky: Financial Interests, Institutional, Research Grant: Agendia, AstraZeneca; Financial Interests, Institutional, Speaker, Consultant, Advisor: AstraZeneca, Pfizer, Novartis, Eli Lilly, Genentech/Roche, Seagen, Daiichi Sankyo, Merck, Agendia, Sanofi, Myriad, Gilead, Puma. R. Sandin: Financial Interests, Personal, Stocks/Shares, Rickard Sandin is an employee and stockholder of Pfizer: Pfizer. S. Karanth: Financial Interests, Institutional, Funding, Full-time employee of RTI Health Solutions, an independent non-profit research organization, which was retained by Novartis to conduct the research that is being submitted to ESMO. Compensation is unconnected to the studies on which I work.: Novartis; Financial Interests, Institutional, Funding, Full-time employee of RTI Health Solutions, an independent non-profit research organization, which was retained by Pfizer to conduct the research that is being submitted to ESMO. Compensation is unconnected to the studies on which I work.: Pfizer. A. Cha-Silva: Financial Interests, Personal, Stocks/Shares, Ashley Cha-Silva is an employee and stockholder of Pfizer.: Pfizer. D. Makari: Financial Interests, Personal, Stocks/Shares, Doris Makari is an employee and stockholder of Pfizer: Pfizer. S. Stergiopoulos: Financial Interests, Personal, Stocks/Shares, Stella Stergiopoulos is an employee and stockholder of Pfizer: Pfizer; Financial Interests, Personal, Stocks/Shares: EQRx Inc, Roche. R. Goyal: Financial Interests, Institutional, Funding, Full-time employee of RTI Health Solutions, an independent non-profit research organization, which was retained by Pfizer to conduct the research that is being submitted to ESMO. Compensation is unconnected to the studies on which I work: Pfizer. All other authors have declared no conflicts of interest.