An exploratory analysis of patients with advanced breast cancer (ABC) participating in the PALOMA-3 trial identified prognostic factors for overall survival (OS) in patients treated with the cyclin-dependent kinase 4/6 (CDK4/6) inhibitor palbociclib. The researchers reported their findings in the journal The Oncologist.

The post hoc, exploratory analysis was based on data from the phase 3 PALOMA-3 trial (ClinicalTrials.gov Identifier: NCT01942135). This trial evaluated the use of palbociclib with fulvestrant in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer that progressed on prior endocrine therapy. In the trial, patients were randomly assigned on a 2:1 basis to receive either palbociclib with fulvestrant or placebo with fulvestrant. This post hoc study used multivariable analyses to evaluate survival outcomes with respect to multiple patient clinical and treatment characteristics.

A total of 521 patients were included in this analysis. Multivariable analyses revealed endocrine sensitivity, nonvisceral disease, Eastern Cooperative Oncology Group performance status of 0, and lack of prior chemotherapy for advanced breast cancer to be prognostic factors for improved OS outcomes in this study.


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Notably, median OS in patients who had received no prior chemotherapy was longer in the palbociclib-fulvestrant arm (39.7 months) than in the placebo-fulvestrant arm (29.5 months; hazard ratio [HR], 0.75; 95% CI, 0.56-1.01). In patients who had received prior chemotherapy, median OS was similar in both arms (25.6 months and 26.2 months, respectively; HR, 0.91; 95% CI, 0.63-1.32).

The researchers noted that this OS difference based on prior chemotherapy treatment was in contrast to a more consistent progression-free survival benefit seen with palbociclib-fulvestrant in the primary analysis regardless of prior chemotherapy status.

“Taken together, these findings in combination with the current body of literature regarding OS benefit with CDK4/6 inhibitors suggest that patients receive greater clinical benefit from palbociclib plus fulvestrant if the combination is received prior to chemotherapy for treatment of HR+/HER2- [advanced breast cancer],” the researchers concluded.

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

Reference

Rugo HS, Cristofanilli M, Loibl S, et al. Prognostic factors for overall survival in patients with hormone receptor-positive advanced breast cancer: analyses from PALOMA-3. Oncologist. 2021;26(8):e1339-e1346. doi:10.1002/onco.13833