Expression of Programmed Death Ligand 1 (PD-L1) in Breast Cancer patients in India and its Correlation with Prognostic Parameters

The PD-1/PD-L1 pathway represents an adaptive immune resistance mechanism that is exerted by tumor cells. The study was conducted to evaluate the expression of PD-L1 in breast carcinoma in India and to find out its correlation with prognostic parameters. Despite numerous studies, there is a lack of literature for such studies in Indian patients. Moreover, the results obtained from these studies have not been uniform.

A hospital-based cross-sectional study was conducted on 150 cases of breast carcinoma. The invasive cancer specimens were assessed for routine microscopy and classified into various histopathological subtypes. Bloom Richardson grading was done. Immunohistochemistry for surrogate molecularclassification as well as PD-L1 was performed. PD-L1 expression was then compared with several prognostic parameters such as tumor subtype, tumor grade, surrogate molecular classification and pTNM stage. Data analysis was done using Statistical Package for Social Sciences (SPSS) version 21.0. A P value of <0.05 was considered statistically significant.

PD-L1 was positive in 14.67% of patients with score 1 in 6% and score 2 in 8.67% of patients. The PD-L1 expression showed a positive correlation with the tumor of higher grades (grade3). It was significantly higher among IBC with medullary features as compared to IBC-NST, IBC with papillary features and the Lobular type. PD-L1 showed a significant association with surrogate molecular classification as well. Its expression was found to be the highest in Triple negative breast cancer subtype as compared to tumors showing ER/PR positivity (p<0.05). However, there was no significant association between PD-L1 and TNM staging.

This study revealed asignificant association between PD-L1 several prognostic factors such as higher tumor grade (grade3), Triple Negative breast cancer, and IBC with the medullary pattern subtype. The association between PD-L1 and such prognostic parameters signifies its role in tumor mechanism and makes it a potential target for immunotherapy especially in Triple Negative breast cancer cases which lack specific targeted therapies. Moreover, paucity of literature on PD-L1 in breast cancer patients in India and the data showing conflicting results make this study valuable. Our study shall be helpful in further adding to the knowledge of PD-L1 expression in breast cancer especially in Indian women.