Comparing the effectiveness and safety of trastuzumab emtansine plus pertuzumab versus taxane plus trastuzumab plus pertuzumab in patients with high-risk HER2+ early breast cancer.

This study compared the effectiveness and safety of trastuzumab emtansine (T-DM1; Kadcyla) plus pertuzumab (Perjeta) versus taxanes plus trastuzumab (Herceptin) plus pertuzumab (THP) in patients with high-risk HER2-positive (+) early breast cancer (BC) after previous treatment with anthracycline-based chemotherapy. The data showed that both regimens had similar effectiveness and the THP regimen remained the standard of care for these patients.

BC is classified into different subtypes depending on the presence or absence of certain receptors (proteins found on the surface of the cancer cells). HER2 (human epidermal growth factor receptor 2) is a protein that promotes the growth of some BC. This subtype of BC is called HER2-positive (HER2+) BC. There are many treatment options for early-stage HER2+ BC.

The standard care for advanced HER2+ BC is THP (taxanes + trastuzumab + pertuzumab). Trastuzumab and pertuzumab are targeted therapy drugs used to treat metastatic HER2+ BC. Trastuzumab and pertuzumab lock onto HER2 and inhibit its actions. Taxanes are chemotherapy drugs such as docetaxel (Taxotere) or paclitaxel (Taxol). Trastuzumab emtansine (T-DM1) is a drug like trastuzumab used in patients with BC that have high levels of HER2. This is a molecule that specifically targets cancer cells and reduces the side effects to normal cells.

It is not known whether T-DM1 plus pertuzumab or THP works better in patients with high-risk HER2+ early BC after previous treatment with anthracycline-based chemotherapy.

This study involved 1846 women with high-risk HER2+ early BC. Patients were randomly assigned into 2 groups after previous treatment with anthracycline-based chemotherapy. Group 1 included 918 patients who received THP regimen. Group 2 included 928 patients who received T-DM1 plus pertuzumab. The average follow-up time was 57 months for group 1 and 57.1 months for group 2.

After 3 years, 94.2% of the patients in group 1 were alive without any signs or symptoms of cancer (disease-free) compared to 93.1% of the patients in group 2. This difference was not significant.

Overall, 88.4% of the patients in group 1 completed the treatment compared to 65% of the patients in group 2.

The rate of serious side effects was similar between the 2 groups (23.3% in group 1 vs 21.4% in group 2).

This study concluded that both regimens showed similar effectiveness. The authors suggested that the THP regimen should remain the standard of care for patients with high-risk HER2+ early BC.

This study was sponsored by F. Hoffmann-La Roche Ltd and Genentech, the manufacturers of T-DM1.