Comparing the effectiveness and safety of combined therapy of pertuzumab with trastuzumab versus single trastuzumab therapy in patients with HER2-positive advanced breast cancer

The study compared the effectiveness and safety of pertuzumab (Perjeta) and trastuzumab (Herceptin) combined therapy with trastuzumab alone in patients with HER2-positive (HER2+) advanced breast cancer (BC). The study found that the combined therapy was more effective and well tolerated compared to single therapy in these patients. 

HER2+ BC is a type of BC that tests positive for a protein known as human epidermal growth factor receptor 2 (HER2). This protein promotes the growth of breast cancer cells. The current treatment for HER2+ BC is a combination of surgery, chemotherapy, and targeted cancer drugs.

Trastuzumab is a targeted cancer drug that attaches to the HER2 protein on cancer cells and stops the growth of BC cells. It is more effective when it is combined with chemotherapy. Another targeted cancer drug that works the same way is pertuzumab. Pertuzumab is also more effective when used together with trastuzumab or chemotherapy. Both drugs are used to treat early-stage or advanced breast cancer.

It has been proven that dual therapy is effective and safe but can cause heart-related problems. However, it is unknown whether combined trastuzumab and pertuzumab therapy will increase the frequency of side effects compared to single trastuzumab therapy.

This study analyzed the results of 14 other studies including a total of 8,738 patients with HER2+ BC. Patients were treated with either pertuzumab plus trastuzumab or trastuzumab emtansine (Kadcyla) – group 1 (4241 patients) or trastuzumab or trastuzumab emtansine alone – group 2 (4137 patients). The effectiveness and safety were compared among groups. 

Patients in group 1 had a 23% higher chance of a better overall survival compared to group 2. Patients in group 1 also had a 26% higher chance of surviving without cancer worsening compared to group 2.   

There was an increase in the frequency of side effects such as low red and white blood cell counts, diarrhea, and heart failure in group 1 compared to group 2. Overall there was no significant difference in serious side effects between the groups. However, in Asian patients, there was a significantly higher risk of serious side effects associated with combined therapy compared to trastuzumab alone. 

The study concluded that dual therapy of trastuzumab and pertuzumab is safe and has better outcomes for patients with HER2+ advanced BC compared to using trastuzumab alpne.

A longer duration of study is needed to evaluate the serious adverse effects of dual therapy in Asian patients.