Safety and effectiveness of pembrolizumab and radiotherapy in patients with metastatic triple-negative breast cancer

This study aimed to investigate the effectiveness and safety of pembrolizumab and radiotherapy in patients with metastatic triple-negative breast cancer. 

This study concluded that this combination was found to be safe and promising in these patients. 

Pembrolizumab (Keytruda) is a targeted therapy used in cancer immunotherapy (targets the immune system to attack cancer cells). It has previously been used to treat melanoma, Hodgkin lymphoma, head, lung, stomach and neck cancers.  

Radiotherapy is a commonly used cancer treatment. It uses high doses of radiation to kill cancer cells and shrink tumors. It can be used after surgery for patients with breast cancer (BC).  

It was not known if the combination of pembrolizumab and radiotherapy was safe and effective in patients with metastatic (spread to distant organs and tissues) triple-negative BC (mTNBC) and poor-prognosis. 

This study involved 17 patients with mTNBC. Patients were treated with pembrolizumab and radiotherapy. Patients were followed for an average of 34.5 weeks. The main outcome measured was the overall response rate (ORR) at week 13. The other outcome measured was safety and progression-free survival (PFS).  

The ORR for the group was 17.6%. Three patients had complete responses (CRs), one had stable disease and thirteen had progressive disease. Of the nine women who were assessed at week 13, three (33%) achieved a CR, with a 100% reduction in tumor volume outside of the irradiated area. The CRs lasted for 18, 20 and 108 weeks.  

29% of patients experienced mild skin inflammation as a side effect. Fatigue, lymphopenia (low level of white blood cells) and infection were moderate side effects related to pembrolizumab. No serious side effects or treatment-related deaths were reported. 

This study concluded that the combination of pembrolizumab and radiotherapy was found to be safe and promising in patients with poor-prognosis mTNBC. 

This was a very small phase 2 study. Larger and longer-term studies are needed to evaluate the safety and effectiveness of this treatment combination.