What factors can predict if melanoma patients respond to anti-PD-1 immunotherapy?

This study investigated whether there was a relationship between specific tumor characteristics (biomarkers) in melanoma patients and response to anti-PD-1 immunotherapy. This study found that patients with certain tumor characteristics had a better response to anti-PD-1 immunotherapy and experienced increased survival.

Anti-PD1 immunotherapy works by activating the body's immune system to kill tumor cells.The presence of a protein called PD-L1 in the tumors of patients with melanoma is associated with a better response to anti-PD-1 immunotherapy. However, it can be difficult to determine if this protein is present in tumors. It is important to investigate if there are other proteins or specific tumor characteristics that can be used to predict if melanoma patients will respond to anti-PD1 immunotherapy.

This study analysed data previously collected from 70 patients  with melanoma before they started anti-PD1-immunotherapy. The tumor samples were analysed for specific tumor characteristics and the patients overall response rate to therapy at 6 months after treatment was also analysed.

Specific tumor characteristics included: metachronous metastases (MM – tumor spreading to new area 3 months after an operation), if the tumour or immune cells contained the protein PD-L1, if the immune cells around the tumor contained a protein called CD163, if the tumour had a mutation (change) in the gene NRAS.

The results found that patients with melanoma who had MM, PD-L1 on their tumor- and/or immune-cells, CD163 on the immune cells around the tumor, and a change in the gene NRAS in the melanomas responded better to anti-PD1 immunotherapy.

CD163 on immune cells around the tumor was also associated with longer progression-free survival (PFS – survival without disease getting worse), and MM was associated with longer overall survival and PFS.

The study concluded that PD-L1 status alone cannot be used to reliably predict response to anti-PD-1 immunotherapy but could be combined with other criteria such as type of spread and proteins on the cancer cells.

This study analysed data that was previously collected and from a small number of patients which may have affected the results.