PD-L1 expression and pattern of immune cells in pre-treatment specimens are associated with disease-free survival for HR-NMIBC undergoing BCG treatment.

PURPOSE: To assess the association between PD-L1 expression and disease-free survival (DFS) in High-Risk Non-Muscle Invasive Bladder Cancer (HR-NMIBC) patients treated with intravesical Bacillus Calmette-Guerin (BCG) instillations (IBI). METHODS: Retrospective study in five French centres between 2001 and 2015. Participants were 140 patients with histologically confirmed HR-NMIBC. All patients received induction and maintenance IBI. Pathological stage/grade, concomitant carcinoma in situ, lesion number and tumour size were recorded. CD3, CD8 and PD-L1 expression in tumour cells and in T cells in the tumour microenvironment (TME) was determined immunohistochemically. Median follow-up was 54.2 months. The primary outcome measure was DFS. Univariable and multivariable analyses were performed using the log rank test and Cox proportional hazards model. RESULTS: Of the 140 NMIBC, 52 (37.1%) were Ta, 88 (62.9%) were T1 and 100% were high grade. Median number of maintenance IBI was six (range 1-30). Twenty-five (17.9%) patients had recurrence/progression. In multivariable analysis, age (HR 1.07 [95% CI 1.02-1.13], p = 0.009), PD-L1 expression in tumour cells (HR per 10 units = 1.96 [95% CI 1.28-3.00], p = 0.02) and CD3/CD8 ratio (HR per 10 units = 3.38 [95% CI 1.61-7.11], p = 0.01) were significantly associated with DFS. However, using the cut-off corresponding for each PD-L1 antibodies, PD-L1 + status was not associated with DFS. CONCLUSION: Despite an association between PD-L1 expression and BCG failure in HR-NMIBC, the PD-L1 + status was not a prognostic factor in the response of BCG. Moreover, we confirmed the key role played by the IC within the microenvironment in BCG treatment. These findings highlighted the rationale to combine BCG and PD-L1/PD-1 antibodies in early bladder cancer.