442P - Menopausal status may derive in different second-line treatment benefits in breast cancer patients that experienced disease progression with CDK4/6 inhibitors (SUMA-001)

Background

CDK4/6 inhibitors added to hormone therapy (CDKi-HT) is the standard first-line (1L) treatment for patients with HR+/HER2- advanced breast cancer (ABC). After CDKi-HT, treatment strategies are associated with shorter progression-free survival (PFS), and therapeutic strategies are usually tailored to clinical factors and predictive biomarkers. Our aim was to explore prognostic factors in the second-line (2L) treatment setting and determine clinical factors associated with treatment efficacy.

Methods

Retrospective cohort of HR+/HER2- ABC patients, from 17 public and private facilities in Argentina. Patients were included if started 2L treatment between November 2015 and October 2022. Clinical factors associated with treatment decisions were evaluated with t and chi-square tests. Kaplan-Meier method was used for survival analysis. Cox regression tests were applied to explore prognostic factors. p<0,05 was considered statistically significant.

Results

280 patients were analyzed (Mean age 52.4+/-14, 57% postmenopausal). 98.5% received CDKi-HT in the 1L setting (med. PFS 17.8m, CI95% 8.1-28.4). Among the 240 patients with evaluable data, 39.2% received chemotherapy (CT) for the 2L setting and 53.7% received hormone therapy with or without other agents. With a median follow-up of 26 months, med. 2L-PFS was 6.6 months (CI 95% 5.8-7.6). After applying multivariate analysis, menopausal status (adj. HR 0.65 CI95% 0.44-0.98; p=0.038) and primary sample Ki67 (adj. HR 2.37 CI95% 1.14-4.9, p=0.02) were associated with 2L-PFS. An interaction was observed between selected treatment agents and menopausal status (p=0.015). In patients that did not receive CT, Median 2L-PFS was 4.66 (CI95% 4.06-6.03) and 8.7 (CI95 7-11.16) months for premenopausal and postmenopausal patients respectively (p=0.0006).

Conclusions

Real-world evidence is relevant to obtain further information regarding prognostic and predictive factors. Treatment selection should be carefully individualized in patients that experienced disease progression after CDKi-HT. The implications of our results should be carefully analyzed incorporating the experiences of other collaborative efforts.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.