Programmed death ligand 1 expression in diffuse large B cell lymphoma: correlation with clinicopathological prognostic factors.

BACKGROUND

The prognostic value of the level of programmed death ligand 1 (PD-L1) expression in non-Hodgkin lymphoma (NHL) is still debatable. This study examined the effect of the level of PD-L1 expression on the clinicopathological characteristics and prognosis of diffuse large B cell lymphoma (DLBCL).

METHODS

A retrospective study was conducted on formalin-fixed paraffin-embedded tissue blocks of one hundred de novo DLBCL patients diagnosed from 2013 to 2016. PD-L1 expression was defined by a modified Combined-Positive Score (CPS) and their medical records were reviewed to collect their clinical, laboratory and radiological data, treatment, and outcome.

RESULTS

The included patients were aged from 23 to 85 years and treated by rituximab- cyclophosphamide, doxorubicin, oncovin, prednisone (R-CHOP); 49% were males; 85% of the cases were presented at Ann Arbor stages III, IV; 33% of patients were seropositive for HCV and 87% of cases were presented with intermediate and high IPI. All included cases expressed PD-L1 using modified CPS. 27% of patients showed low PD-L1 expression (≥ 5% to < 50% of total tumor cellularity) while 73% of patients showed high PD-L1expression (≥ 50% of total tumor cellularity). High PD-L1 expression is statistically correlated with advanced stage (p 0.01), high IPI score (p 0.017), high incidence of stationary and progressive disease (p 0.002) and high incidence of relapse (p value 0.01). Five-year disease-free survival (DFS) was 29% for patients with high PD-L1 expression compared with 84.8% for patients with low PD-L1 expression (p 0.001).

CONCLUSIONS

This study suggests that high PD-L1 expression in DLBCL is associated with aggressive clinicopathological features and a decreased response to R-CHOP. The level of PD-L1 expression could be an independent predictor of DFS of DLBCL. More research is mandatory to standardize the cutoff value and scoring methods.