Clinical relevance of the comparative expression of immune checkpoint markers with the clinicopathological findings in patients with primary and chemoreduced retinoblastoma.

The goal of this study is to identify the pathological findings and expression of immune checkpoint marker (PD-1, PD-L1, and CTLA-4) in the tumor microenvironment of both primary and chemoreduced retinoblastoma and correlate them with clinicopathological parameters and patient outcome. Total of 262 prospective cases was included prospectively in which 144 cases underwent primary enucleation and 118 cases received chemotherapy/radiotherapy before enucleation (chemoreduced retinoblastoma). Immunohistochemistry, qRT-PCR and western blotting were performed to evaluate the expression pattern of immune checkpoint markers in primary and chemoreduced retinoblastoma. Tumor microenvironment were different for both primary and chemoreduced retinoblastoma. Expression of PD-1 was found in 29/144 (20.13%) and 48/118 (40.67%) in primary and chemoreduced retinoblastoma, respectively, whereas PD-L1 was expressed in 46/144 (31.94%) and 22/118 (18.64%) in cases of primary and chemoreduced retinoblastoma, respectively. Expression pattern of CTLA-4 protein was similar in both groups of retinoblastoma. On multivariate analysis, massive choroidal invasion, bilaterality and PD-L1 expression (p = 0.034) were found to be statistically significant factors in primary retinoblastoma, whereas PD-1 expression (p = 0.015) and foamy macrophages were significant factors in chemoreduced retinoblastoma. Overall survival was reduced in cases of PD-L1 (80.76%) expressed primary retinoblastoma, and PD-1 (63.28%) expressed chemoreduced retinoblastoma. This is the first of its kind study predicting a relevant role of the immune checkpoint markers in both groups of primary and chemoreduced retinoblastoma with prognostic significance. Differential expression of these markers in both group of retinoblastoma is a novel finding and might be an interesting and beneficial target for chemoresistant tumors.