Does pembrolizumab added to chemotherapy before surgery improve the outcomes of patients with early triple negative breast cancer?

The study assessed whether pembrolizumab (Keytruda) could be used in addition to neoadjuvant chemotherapy (NAC; chemotherapy before surgery) to improve the outcomes of patients with early triple-negative breast cancer (TNBC). The study found that more patients treated with pembrolizumab had a complete response.

Triple-negative breast cancer (TNBC) is a type of breast cancer that does not grow in response to female hormones or the protein HER2. TNBC accounts for 10-15% of all breast cancers (BC). TNBC is known to be difficult to treat and usually has a poorer prognosis when compared to other forms of BCs. Breast conservation (removal of the tumor only but not the breast completely) and mastectomy (removal of the entire breast) are often used as surgical treatment for BC. To ensure a better removal of the tumor, patients are often given NAC to shrink the tumor and to kill any cancer cells that have spread from the breast.

Pembrolizumab is an antibody (y-shaped protein produced by the immune system) that is used in the treatment of several cancers. Pembrolizumab has been approved for use as a first line treatment in metastatic TNBC. However, its effectiveness when added to NAC in patients with early TNBC is still under investigation.

There were 1174 patients with early TNBC in this study. Patients had never received treatment for their condition. Patients were randomly assigned to one of 2 treatment groups before undergoing surgery. Group 1 received pembrolizumab plus chemotherapy with paclitaxel (Taxol) and cisplatin (Platinol). Group 2 received a placebo plus paclitaxel and cisplatin. The average follow-up period was 15.5 months. 

In group 1, 64.8% of patients had a pathological complete response (pCR; no cancer left after surgery). In group 2, 51.2% of patients had a pCR. Survival without disease progression was significantly higher in group 1. At 18 months, 91.3% of patients in group 1 and 85.3% of those in group 2 were alive without disease progression. 

Before surgery, serious treatment-related side effects occurred in more patients in group 1 (32.5%) compared to group 2 (19.35%). The most common serious side effects were low white blood cell counts with fever, anemia, and fever. After surgery, side effects related to the treatment occurred in 48.1% of group 1 and 43% of group 2.

The authors concluded that in patients with early TNBC, pembrolizumab added to NAC led to improved responses and survival.

This study was sponsored by Merck, Sharp & Dohme, the manufacturers of pembrolizumab. This study is still ongoing. The long term outcomes of pembrolizumab added to NAC in patients with early TNBC are still under investigation.