25 A Retrospective Cohort Study of Demographic, Clinical, and Treatment Characteristics of Patients With Metastatic Breast Cancer Who Have Received PARP Inhibitors

Jenna Collins, MPH¹; Beth Nordstrom, PhD, MPH¹; Stella Mokiou, PhD²; Brian Murphy, MS¹; Melissa Pavilack, PharmD³

¹Evidera, Waltham, MA

²AstraZeneca, Cambridge, United Kingdom

³AstraZeneca Pharmaceuticals, Gaithersburg, MD

Background

PARP inhibitors (PARPi) were approved in 2018 as treatment for metastatic breast cancer (mBC) and have demonstrated efficacy in patients with a germline BRCA mutation (gBRCAm). Limited real-world data exist on the characteristics of patients who are treated with PARPi, and at what point during their treatment they are receiving these agents.

Material and methods

This is a retrospective cohort study of patients receiving a PARPi for mBC in routine clinical practice, using data from the Flatiron Health electronic health record–derived database. The study population comprised adult patients in the United States, diagnosed between 2013 and 2019 with mBC, identifiable as hormone receptor–positive (HR+) or with triple-negative breast cancer (TNBC). Patients were treated with a PARPi (olaparib [Lynparza] or talazoparib [Talzenna]) between December 1, 2014, when the first PARPi approval for any indication occurred, and December 31, 2019. Patient demographic and clinical characteristics were examined. Treatment patterns prior to first PARPi use were described, both overall and by line of therapy. Results were stratified for patients with HR+ and TNBC.

Results

In total, 137 patients were included; 100 patients (73%) had HR+ mBC and 37 (27%) had TNBC, and the median age at PARPi initiation was 54 and 49 years, respectively. Stage at initial diagnosis was most commonly stage II (35.0% and 32.4% for HR+ and TNBC, respectively), or III (32.0% and 32.4%, respectively). The gBRCAm status was documented for 87.0% of patients with HR+ and 83.8% with TNBC and 88.5% and 80.6% of those patients, respectively, had a gBRCAm. Most TNBC patients first received a PARPi in the first or second line (35.1% each); patients with HR+ disease typically received a PARPi in later lines (23.0% in the third and 43.0% in the fourth line or later). Most patients received their first PARPi as monotherapy (75.0% and 83.8% of patients with HR+ and TNBC, respectively). Of the patients with first PARPi use in the second line or later, 27.6% of patients with HR+ status and 50.0% of those with TNBC received platinum chemotherapy prior to PARPi initiation; 60.9% of patients with HR+ mBC received cyclin-dependent kinases 4 and 6 inhibitors before their first PARPi.

Conclusions

This study provides an early look at PARPi utilization before and during the 2 years following approval for mBC. Patients with HR+ mBC most often received PARPi during later lines of therapy, whereas those with TNBC received the inhibitor earlier. PARPi were typically used as monotherapy. Further assessment of clinical outcomes by line of therapy in future studies is warranted.