Abstract CT071: Talazoparib (TALA) in germline BRCA1/2 (gBRCA1/2)-mutated human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer (ABC): Final overall survival (OS) results from randomized Phase 3 EMBRACA trial
Authors: Litton Jennifer K. , Hurvitz Sara A. , Mina Lida A. , Rugo Hope S. , Lee Kyung-Hun , Gonçalves Anthony , Diab Sami , Woodward Natasha , Goodwin Annabel , Yerushalmi Rinat , Roché Henri , Im Young-Hyuck , Eiermann Wolfgang , Quek Ruben G. , Usari Tiziana , Lanzalone Silvana , Czibere Akos , Blum Joanne L. , Martin Miguel , Ettl Johannes 
Published: September 2020

Background: TALA significantly prolonged progression-free survival vs physician's choice of chemotherapy (PCT) (hazard ratio [HR] 0.54 [95% CI 0.41-0.71]; P &lt; 0.001) and improved patient-reported outcomes (PRO) in patients (pts) with HER2- ABC (locally advanced/metastatic) with a gBRCA1/2 mutation. We report results of the final OS analysis (secondary endpoint).

Methods: Pts randomized 2:1 to TALA or PCT. OS HR was based on stratified Cox regression model (treatment as covariate); P value on stratified log-rank test.

Results: 431 pts were randomized (287 TALA/144 PCT), 412 treated (286 TALA/126 PCT). By Sept 30, 2019, 216 deaths (75.3%) occurred for TALA and 108 deaths (75.0%) PCT; median follow-up 44.9 and 36.8 months, respectively. HR for OS was 0.85 (95% CI 0.67-1.07; P = 0.17); survival probability was higher for pts receiving TALA at 24, 36, and 48 months (Table 1). OS results were consistent across subgroups, eg by prior platinum or hormone receptor status. Most pts received post-study therapies; 32.6% of pts in the PCT arm received a PARP inhibitor post-study (4.5% for TALA arm). Grade 3-4 AEs occurred in 69.6% (TALA) and 64.3% (PCT) pts; AEs leading to permanent treatment discontinuation (excluding progressive disease) occurred in 5.9% and 8.7% of pts. Extended follow-up showed statistically significant overall improvements and delays in time to definitive clinically meaningful deterioration in both global health status/QoL and breast symptoms scales favoring TALA vs PCT (P &lt; 0.01 for all), consistent with initial PRO analyses.

Table 1.OS and post-study therapy (intent-to-treat)Talazopariboral 1 mg QDN = 287PCTaN = 144Deaths (%)216 (75.3)108 (75.0)HR (95% CI)0.85 (0.67-1.07); P = 0.17Median, mo. (95% CI)b19.3 (16.6-22.5)19.5 (17.4-22.4)Survival probability (95% CI) at Monthc120.71 (0.66-0.76)0.74 (0.66-0.81)240.42 (0.36-0.47)0.38 (0.30-0.47)360.27 (0.22-0.33)0.21 (0.14-0.29)480.19 (0.14-0.25)0.07 (0.02-0.15)Post-study antineoplastic therapy, n (%)233 (81.2)110 (76.4)PARP inhibitor, n (%)13 (4.5)47 (32.6)Platinum-based therapy, n (%)133 (46.3)60 (41.7)CI, confidence interval; HR, hazard ratio; KM, Kaplan-Meier; mo., months; OS, overall survival; PARP, poly(ADP-ribose) polymerase; QD, once daily.aPCT, physician's choice of chemotherapy (capecitabine, eribulin, gemcitabine, vinorelbine).bDuration of OS based on KM estimates.cProbability estimated from the KM curve and CI calculated with product-limit method.

Conclusions: In gBRCA1/2-mutated HER2- ABC, TALA did not significantly improve OS over PCT (HR 0.85; 95% CI 0.67-1.07; P = 0.17); analysis not adjusted for subsequent therapies. TALA was generally well-tolerated with no new safety signals. PRO continued to favor TALA.

Funding: Pfizer (Medivation)

Citation Format: Jennifer K. Litton, Sara A. Hurvitz, Lida A. Mina, Hope S. Rugo, Kyung-Hun Lee, Anthony Gonçalves, Sami Diab, Natasha Woodward, Annabel Goodwin, Rinat Yerushalmi, Henri Roché, Young-Hyuck Im, Wolfgang Eiermann, Ruben G. Quek, Tiziana Usari, Silvana Lanzalone, Akos Czibere, Joanne L. Blum, Miguel Martin, Johannes Ettl. Talazoparib (TALA) in germline BRCA1/2 (gBRCA1/2)-mutated human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer (ABC): Final overall survival (OS) results from randomized Phase 3 EMBRACA trial [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT071.