Does pembrolizumab improve survival of patients with metastatic non-small-cell lung cancer in the long term?

This study evaluated the long-term effectiveness of pembrolizumab (Keytruda) in patients with untreated metastatic non-small cell lung cancer (NSCLC). The authors showed that pembrolizumab increased the long-term survival of patients compared to chemotherapy.

NSCLC accounts for most lung cancers. Treatment choice might include surgery if the tumour is still localized in the lung, while radiotherapy, chemotherapy, and immunotherapies are chosen for more advanced disease. 

Immunotherapies are drugs that promote cancer death by enforcing the immune system to detect the cancer. An example of immunotherapy used for NSCLC is pembrolizumab. Some cancer cells have on their surface a protein that hides cancer cells from the immune system. Pembrolizumab blocks this protein, making the immune system able to detect and kill cancer cells. 

Pembrolizumab has improved the survival of patients with advanced NSCLC compared to standard chemotherapy. However, the long-term effectiveness of this treatment is still under investigation.

This trial included 305 patients with previously untreated advanced NSCLC. Patients were randomly assigned to receive either pembrolizumab (154 patients) or chemotherapy (151 patients). Among chemotherapy-treated patients, 66% switched on to receive immunotherapy after disease progression. The average follow-up was 59.9 months.

The average survival was significantly higher in the pembrolizumab group (26.3 months) compared to the chemotherapy group (13.4 months). Pembrolizumab was associated with a 38% higher chance of survival compared to chemotherapy.

31.9% of patients treated with pembrolizumab were still alive after 5 years, compared to 16.3% of patients treated with chemotherapy. 

The survival benefit with pembrolizumab was seen not only in patients with a complete or partial response to therapy, but also in patients with stable disease (cancer did not grow or spread).

No new side effects were reported to pembrolizumab treatment with longer follow-up. 

This study concluded that pembrolizumab improves the survival of patients with untreated metastatic NSCLC in the long term.

A high number of patients in the chemotherapy group crossed over to receive immunotherapy. This might have reduced the magnitude of the response to pembrolizumab. This study was funded by Merck, the manufacturer of pembrolizumab.