A study that looked into France’s RENAPE Observational Registry, a database of rare peritoneal tumors, found that the presence of programmed death-ligand 1 (PD-L1) on immune cells in epithelioid peritoneal malignant mesothelioma (EPMM) could help to predict overall and progression-free survival.
Results of the study, “Immunohistochemical evaluation of two antibodies against PD-L1 and prognostic significance of PD-L1 expression in epithelioid peritoneal malignant mesothelioma: A RENAPE study,” were recently published online in the European Journal of Surgical Oncology.
Programmed death-ligand 1 (PD-L1) is a protein that may play a major role in suppressing the immune system. PD-L1 is emerging as a therapeutic and diagnostic tool, of use in identifying appropriate therapies for individual patients.
The ability of two different monoclonal antibodies to detect PD-L1 were compared, and one of them, E1L3N, proved to be useful in evaluating the presence of PD-L1 on tumor cells and immune cells in EPMM specimens.
Researchers looked for PD-L1 both on lymphocytes, a kind of immune cell, and on tumor cells in the 45 EPMM tumors using the two antibodies, E1L3N and SP142. They found that E1L3N detected PD-L1 in 31.1 percent of tumor cells and 15.6 percent of lymphocytes, while SP142 detected PD-L1 in 22.2 percent of tumor cells and 26.7 percent of lymphocytes. The results from the two antibodies agreed in a moderate number of cases and in positive cases, few (1-5 %) tumor cells had PD-L1 on their surfaces, according to this test.
The researchers found E1L3N to be preferable to SP142 in evaluating the presence of PD-L1. They studied 39 cases of EPMM to assess the relevance of PD-L1 expression on patient outcomes, and found that the presence of PD-L1 on lymphocytes, but not on tumors, was predictive of survival times.
“Using E1L3N, PD-L1 expression by lymphocytes was associated with better OS [overall survival] and PFS [progression-free survival] by both univariate and multivariate analysis,” they reported.
The study also looked at outcomes based on treatment and on tumor subtype. It reported that cytoreductive surgery with hyperthermic intraperitoneal chemotherapy — a two-step therapy that involves surgically removing any visible tumor or cancer, and then delivering heated chemotherapy drugs to the affected area — was more effective than other treatments. A solid subtype of tumor, one of five EPMM subtypes, was also associated with poorer survival times.
“E1L3N appeared easier to use than SP142 to evaluate PD-L1 expression. A minority of EPMM expressed PD-L1, and only a few cells were positive. PD-L1 expression by immune cells evaluated with E1L3N was an independent prognostic factor in EPMM,” the study concluded.