A Phase III Trial of Pertuzumab Retreatment in Previously Pertuzumab Treated Her2-Positive Advanced Breast Cancer

The purpose of this study is to evaluate the efficacy and safety of pertuzumab, trastuzumab and chemotherapy as a pertuzumab retreatment compared to trastuzumab and chemotherapy in locally advanced or metastatic breast cancer patients for previously treated with pertuzumab

The American Society of Clinical Oncology (ASCO) Clinical Practice Guidelines recommend the use of pertuzumab, trastuzumab and taxane as first-line treatment for patients with MBC. As a second-line treatment, trastuzumab emtansine (T-DM1) is also recommended. After a pertuzumab-containing regimen and T-DM1, other HER2-targeted therapeutic regimens, including lapatinib-containing regimens and trastuzumab plus chemotherapy, are recommended as third-line treatments and beyond. However, continual pertuzumab use for progression after a pertuzumab-containing regimen and retreatment with pertuzumab are unclear based on evidence. The efficacy and the safety of two distinct modalities of a trastuzumab plus pertuzumab-containing regimen after pertuzumab use should be assessed in MBC: continual treatment and retreatment. However, it is clinically difficult to examine the efficacy of continual treatment with a trastuzumab plus pertuzumab-containing regimen because of several circumstances including the results of the MARIANNE study. In addition, it is also important to evaluate the usefulness of retreatment with a pertuzumab-containing regimen. Continual pertuzumab treatment for progression after pertuzumab treatment is not same as pertuzumab retreatment. HER2-HER3-signaling suppressed by pertuzumab-containing regimens could potentially be restored by anti-HER2 therapy without pertuzumab. Pertuzumab retreatment could potentially re-suppress HER2-HER3-signaling. Therefore, Pertuzumab retreatment can be more effective than trastuzumab-containing treatment without pertuzumab.