Long-term outcomes of pertuzumab added to trastuzumab and docetaxel treatment for patients with advanced HER2-positive breast cancer

This study looked at whether pertuzumab (Perjeta) benefits patients with metastatic HER2-positive breast cancer when added to trastuzumab (Herceptin) and docetaxel (Taxotere) treatment. They found that adding pertuzumab improved long-term patient outcomes.

Breast cancer can now be tested for some of the signals involved in its growth. HER2 kinase is a protein that activates growth in breast tissue. Breast cancer which has an abnormally high amount of HER2 tends to grow aggressively. This is particularly true when the cancer is metastatic, meaning it has spread outside the breasts.

Trastuzumab was the first therapy to target HER2. It utilizes antibodies (small molecules from the immune system) that bind to a specific target. Trastuzumab improved outcomes for metastatic HER2-positive breast cancer. Docetaxel is a chemotherapy used for the treatment of breast cancer. It blocks cell division and caused cancer cells to die.

Pertuzumab is another HER2-targeted antibody therapy. Adding pertuzumab to trastuzumab and chemotherapy improves short-term outcomes for metastatic HER2-positive breast cancer. It is unclear whether pertuzumab improves long-term outcomes in these patients.

This study followed 808 patients in 25 countries with metastatic HER2-positive breast cancer. 402 patients received pertuzumab, and 406 received a placebo. Additionally, all patients received treatment with trastuzumab and docetaxel. Patients were followed for an average of 99.9 months for the pertuzumab group and 98.7 months for the placebo group.

The five-year survival rate was significantly higher in the pertuzumab group than the placebo group (49% vs. 35%). The eight-year survival was also significantly higher in the pertuzumab group (37% vs. 23%).

The average time before the cancer progressed (became worse) was significantly longer for the pertuzumab group (18.7 vs. 12.4 months). 16% of patients in the pertuzumab group had no progression after eight years. A long-term response was more common when the cancer did not have a PIK3CA mutation.

The most common serious side effect for both groups was low white blood cell count (49% for pertuzumab vs. 46% for placebo). Diarrhea and rash were more common in the pertuzumab group.

This study found that adding pertuzumab to trastuzumab and docetaxel improved long-term outcomes for patients with metastatic HER2-positive breast cancer.

This was a continuation of the Phase III study which led to FDA approval of Perjeta for HER2-positive metastatic breast cancer. The authors work with pharmaceutical companies including Genentech, which developed Perjeta.