Pertuzumab, Trastuzumab, Capecitabine May Prolong Overall Survival in HER2-Positive Breast Cancer
Although progression-free survival was not significantly increased, long-term overall survival may be improved with pertuzumab.
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Adding pertuzumab to trastuzumab and capecitabine prolongs overall survival (OS) among patients with HER2-positive metastatic breast cancer (MBC) who had previously failed trastuzumab-based therapy compared with trastuzumab and capecitabine alone, according to findings to be presented at the American Society of Clinical Oncology (ASCO) 2018 Annual Meeting in Chicago, Illinois.1
Results of the PHEREXA (ClinialTrials.gov Identifier: NCT01026142) previously demonstrated that although progression-free survival (PFS) was not significantly improved with the combination of pertuzumab, trastuzumab, and capecitabine in this population, longer-term data showed that there may be prolongations of OS.
In the two-arm, phase 3 PHEREXA study, researchers randomly assigned 452 patients with HER2-positive MBC to receive intravenous (IV) trastuzumab 8 mg/kg as a loading dose followed by 6 mg/kg every 3 weeks and oral capecitabine 1000 to 1250 mg twice daily. Patients in the experimental arm in addition received intravenous pertuzumab 840 mg loading dose followed by 420 mg every 3 weeks. Eligible patients had failed previous trastuzumab and taxane therapies.
At the time of data cutoff, the median time on study and follow-up was 23 months among patients in the control arm and 33 months in the experimental arm.
Results showed that PFS was 11.8 months among patients treated with pertuzumab compared with 9.0 months among patients who were not; an increase of 2.8 months that was not considered significant.
Median OS however, was 37.2 months and 28.1 among patients treated with pertuzumab and patients who only received trastuzumab and capecitabine, respectively; a difference of 9.1 months.
The toxicity profile remained consistent with those previously reported, and there were no signs of late-onset cardiac toxicity.
The authors concluded that “while final OS results of PHEREXA are descriptive, median OS of 37.3 months in arm B, with a 9.1-month increase versus arm A, shows that clinical efficacy of [trastuzumab plus pertuzumab] is maintained with longer follow-up.”
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- Urruticoechea A, Rizwanullah M, Im SA, et al. Final overall survival (OS) analysis of PHEREXA: A randomized phase III trial of trastuzumab (H) + capecitabine (X) ± pertuzumab (P) in patients with HER2-positive metastatic breast cancer (MBC) who experienced disease progression during or after H-based therapy. Poster presentation at: 2018 ASCO Annual Meeting; June 1-5, 2018; Chicago, IL.