Real-World Palbociclib Use in HR+/HER2- Advanced Breast Cancer in Canada: The IRIS Study

Abstract

Background: Palbociclib is a selective cyclin-dependent kinase (CDK) 4/6 inhibitor used in combination with aromatase inhibitors or fulvestrant for patients with hormone receptor-positive (HR+) human epidermal growth factor receptor 2 (HER2)-negative advanced/metastatic breast cancer (ABC/MBC). Palbociclib was the first CDK 4/6 inhibitor approved for HR+/HER2- ABC/MBC treatment in Canada in combination with letrozole (P+L) as an initial endocrine-based therapy (approved March 2016), or with fulvestrant (P+F) following disease progression after prior endocrine therapy (approved May 2017). The Ibrance Real World Insights (IRIS) study (NCT03159195) collected real-world outcomes data for palbociclib-treated patients in several countries, including Canada.

Methods: This retrospective chart review included women with HR+/HER2- ABC/MBC receiving P+L or P+F in Canada. Physicians reviewed medical records for up to 14 patients, abstracting demographic and clinical characteristics, treatment patterns, and clinical outcomes. Progression-free rates (PFRs) and survival rates (SRs) at 6, 12, 18, and 24 months were estimated via Kaplan-Meier analysis.

Results: Thirty-three physicians examined medical records for 247 patients (P+L, n = 214; P+F, n = 33). Median follow-up was 8.8 months for P+L and 7.0 months for P+F. Most patients were initiated on palbociclib 125 mg/d (P+L, 90.2%; P+F, 84.8%). Doses were reduced in 16.6% of P+L and 14.3% of P+F patients initiating palbociclib at 125 mg/d. The PFR for P+L was 90.3% at 12 months and 78.2% at 18 months; corresponding SRs were 95.6% and 93.0%. For P+F, 6-month PFR was 91.0%; 12-month SR was 100.0%.

Conclusions: Dose reduction rates were low and PFR and SR were high in this Canadian real-world assessment of P+L and P+F treatments, suggesting that palbociclib combinations are well tolerated and effective.

Keywords: Canada; medical chart review; metastatic breast cancer; palbociclib; real-world; retrospective.

Conflict of interest statement

We have read and understood Current Oncology’s policy on conflicts of interest disclosure and declare the following interests: D.M. and L.Z. are employees of Pfizer Inc. K.M., G.T.-S., and G.M. are employees of Adelphi Real World and were paid consultants to Pfizer in connection with the development of this manuscript.

Figures

Figure 1

Progression-free rate (A) and survival rate (B) in patients treated with palbociclib + letrozole (P+L) and palbociclib + fulvestrant (P+F). N/A = not applicable. a Censored data from patients who remained on treatment in whom a progression event did not occur during the 18–24-month time period. b Censored data from patients who remained on treatment in whom a death event did not occur during the follow-up period. P+F: No 12-, 18-, and 24-month progression-free or 24-month survival data available because of the insufficient follow-up period. For patients who remained on treatment, no death events occurred during the follow-up period. P+L: For patients who remained on treatment, no progression or death events occurred during the 18–24-month follow-up period.

Figure 2

Progression-free rate (A) and survival rate (B) in patients treated with palbociclib + fulvestrant as first-line or second- and later-line therapy. Rates were estimated using Kaplan–Meier analyses.