AI Plus Trastuzumab, Pertuzumab Efficacious in HER2+, HR+ Breast Cancer

In patients with human epidermal growth factor receptor 2 (HER2)-positive, hormone receptor (HR)-positive, metastatic, or locally advanced breast cancer, the addition of pertuzumab to first-line trastuzumab and an aromatase inhibitor is well-tolerated, and is associated with an improvement in progression-free survival compared with trastuzumab and an aromatase inhibitor alone.¹

Results of the phase 2 PERTAIN trial (ClinicalTrials.gov Identifier: NCT01491737), which will be presented at the 2016 San Antonio Breast Cancer Symposium (SABCS), showed that adding pertuzumab to trastuzumab and an aromatase inhibitor significantly reduced the risk of progression or death by 35% vs treatment with trastuzumab and an aromatase inhibitor only (hazard ratio, 0.65; 95% CI, 0.48-0.89; P = .007).

Median progression-free survival was 18.9 months with pertuzumab, trastuzumab, and an aromatase inhibitor, vs 15.8 months with trastuzumab plus an aromatase inhibitor. Median overall survival has not yet been reached in either arm.

In addition, 63.3% (95% CI, 53.5-72.3) of patients who received the 3-drug combination achieved a response compared with 55.7% (95% CI, 45.7-65.3) of those in the 2-drug treatment group, though this difference was not statistically significant (P = .25). Median duration of response was 27.1 months and 15.1 months in the pertuzumab arm and the trastuzumab only arm, respectively (hazard ratio, 0.57; 95% CI, 0.36-0.91; P = .02).

For this study, researchers enrolled 258 postmenopausal women with HER2-positive, HR-positive, metastatic, or locally advanced breast cancer who had not received prior systemic therapy except for endocrine therapy. Participants were randomly assigned 1:1 to receive first-line pertuzumab plus trastuzumab and an aromatase inhibitor (anastrozole or letrozole), or trastuzumab plus an aromatase inhibitor, until disease progression or unacceptable toxicity.

Slightly more than half of patients also received induction therapy with docetaxel or paclitaxel for 18 to 24 weeks prior to the start of endocrine therapy.

Researchers found that 50.4% of patients who received trastuzumab and pertuzumab reported grade 3 or higher adverse events, vs 38.7% of those who received trastuzumab alone. The most common grade 3 or higher adverse events were hypertension, diarrhea, and neutropenia.

Editor’s Note: This article has been corrected to reflect that one arm of the study added pertuzumab to trastuzumab and an aromatase inhibitor.

Reference

1. Arpino G, Ferrero J-M, de la Haba-Rodriguez J, et al. Primary analysis of PERTAIN: A randomized, two-arm, open-label, multicenter phase II trial assessing the efficacy and safety of pertuzumab given in combination with trastuzumab plus an aromatase inhibitor in first-line patients with HER2-positive and hormone receptor-positive metastatic or locally advanced breast cancer. Paper presented at: 2016 San Antonio Breast Cancer Symposium (SABCS); December 6-10, 2016; San Antonio, TX.