Does anti PD-1 therapy in melanoma correlate with PD-1 protein level?

The authors investigated the correlation between the level of PD-1, an important protein in immune system, and clinical response of melanoma patients treated with anti-PD1 therapy. The authors concluded that the level of PD-1 was significantly associated with clinical response in metastatic melanoma patients receiving anti-PD1 therapy. 

In advanced melanoma (stage 3 or 4), cancer spreads from the skin to other parts of the body (metastasis). PD-1, an important protein in immune system, is often elevated in this cancer (PD-1 positive). Anti-PD1 therapy, an immunotherapy, is a treatment option for advanced melanoma. This therapy blocks the PD-1 protein using the body's own immune system. This blocking triggers the system to attack tumor cells and kill them.

However, it is not clear whether level of PD-1 is directly correlated with the clinical response of patients to an anti-PD1 therapy.

In this review, the authors analyzed results from 20 clinical trials examining anti-PD1 therapy in different types of cancer. 11 of these studies, including 4230 patients, looked specifically at metastatic melanoma. 

Patients who had positive PD-1 had a 53% decrease in mortality from melanoma after anti-PD1 therapy, compared to PD-1 negative patients.  The objective response rate (partial or complete disappearance of detectable tumors) for PD-1 positive patients was 45%. This was compared to 27% for PD-1 negative patients.

The authors concluded that PD-1 level was significantly associated with clinical response in metastatic melanoma patients receiving anti-PD1 therapy.