Real-world effectiveness of palbociclib plus endocrine therapy in HR+/HER2- advanced breast cancer: final results from the POLARIS trial

Abstract

Background: Strict eligibility criteria for participation in randomized clinical trials (RCTs) often limit the generalizability of data when applied to a more heterogeneous real-world population. Thus, evidence generated directly from real-world populations, including subgroups underrepresented in RCTs, can help inform routine clinical practice. POLARIS (NCT03280303), a prospective, observational, multicenter, cohort study, evaluated patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC) receiving palbociclib + endocrine therapy (ET) in routine care.

Methods: Demographics, baseline characteristics, and treatment patterns were summarized descriptively. Real-world response and clinical benefit rates, real-world progression-free survival (rwPFS), and overall survival (OS) were summarized descriptively by line of therapy and endocrine partner in the overall cohort and various subgroups.

Results: Between January 2017 and October 2019, 1250 patients (median age of 64.0 years) initiated treatment with palbociclib-based therapy, including 901 in the first-line (1L) setting and 349 in the second-line or later (≥2L) settings. Real-world response and clinical benefit rates with palbociclib + ET were 34.0% and 69.4%, respectively, in 1L, and 21.8% and 57.9% in ≥2L. Median rwPFS was 20.9 (95% CI, 18.7-24.7) and 13.5 (10.6-17.1) months, and median OS was 48.5 (42.0-not estimable) and 37.2 (31.2-40.8) months, with 1L and ≥2L palbociclib + ET, respectively.

Conclusions: Outcomes in this large, heterogeneous, real-world population are generally consistent with previously reported results from clinical trials and other real-world studies, further supporting the use of palbociclib + ET in patients with HR+/HER2- ABC.

Trial registration: NCT03280303 (ClinicalTrials.gov).

Keywords: HR+/HER2−; advanced breast cancer; palbociclib; real-world.

Figure 1.

Treatment patterns at final data cutoff. ^aRepresents patients who, at study entry, received palbociclib with endocrine partners other than letrozole, anastrozole, exemestane, or fulvestrant or received palbociclib with no endocrine partners. Abbreviations: 1L, first-line; 2L, second-line; AI, aromatase inhibitor.

Figure 2.

Real-world response rates and real-world clinical benefit rates by line of therapy and endocrine partner. ^aIncludes data from 20 patients who received 1L treatment with other palbociclib regimens (defined as palbociclib with no endocrine partners, or palbociclib with endocrine partners other than letrozole, anastrozole, fulvestrant, or exemestane), which are reported in Supplementary Table S2. ^bIncludes data from 11 patients who received ≥2L treatment with other palbociclib regimens (defined as palbociclib with no endocrine partners, or palbociclib with endocrine partners other than letrozole, anastrozole, fulvestrant, or exemestane), which are reported in Supplementary Table S2. Abbreviations: 1L, first-line; 2L, second-line; AI, aromatase inhibitor; FUL, fulvestrant; PAL, palbociclib; rwCBR, real-world clinical benefit rate; rwRR, real-world response rate.