Clinical interest of PD-L1 immuno-histochemistry expression as a predictive factor of Bacillus Calmette Guerin (BCG) efficacy in refractory high-risk non-muscle-invasive bladder cancer (NMIBC)

Objective To assess PD-L1 expression in tumor (TC) and tumor infiltrating immune cells (IC) as a predictive factor of BCG therapy failure in high-risk NMIBC. Materials and methods Patients treated with complete resection followed by bladder BCG instillation for high-risk NMIBC were included. Early recurrence (ER) was defined as tumor recurrence after BCG induction course. The association between ER and immuno-histochemistry PD-L1 (E1L3N clone) expression by tumors cells (TC) and tumor infiltrating immune cells (IC) was investigated using an exact Fisher test variant. Results A total of 186 patients were included, of whom 38 (20.4%) were ER, 35 (18.8%) were positive for TC PD-L1 expression and 60 (32.3%) were positive for IC PD-L1. ER was not significantly ( p = 0.97) more frequent in the TC PD-L1 ≥ 1% group ( n = 7, 20.0%) than in the TC PD-L1-negative group ( n = 31, 20.5%). Patients with IC PD-L1 negative had ER in 15 (19.2%) cases and patients with IC PD-L1 ≥ 1% had ER in 23 (21.3%) cases. PD-L1-positive expression for IC (threshold > 1%) was correlated with immune infiltrate density (95.2% dense immune infiltrate vs 47.2% low immune infiltrate, p < 0.05), with increased expression of PD-L1 by IC after BCG therapy ( p = 0.006). Conclusion No association was observed between immuno-histochemistry PD-L1 positivity and ER after BCG therapy. Nevertheless, the relationship between immune infiltrate and PD-L1 positivity confirmed the interest of assessing the immune infiltrate density to define tumor’s profile.