Association of positive Ki-67 and PD-L1 expressions in post neoadjvuant chemotherapy (NAC) radical cystectomy samples with lack of tumor downstaging (TD) and shorter overall survival (OS) in patients with muscle-invasive bladder cancer (MIBC).

Abstract

554 Background: Previous chart review studies have reported that adjuvant chemotherapy after NAC did not clearly increase OS in MIBC cases characterized by a lack of TD. There is an unmet need to develop biomarkers to guide adjuvant therapy for this patient population. High levels of expression of cell proliferation marker Ki-67 are associated with poor outcome in chemotherapy naïve bladder cancer. Expression of PD-L1 has been studied as a potential predictive biomarker for anti-PD1 or PD-L1 therapies in metastatic MIBC. We therefore studied Ki-67 and PD-L1 expression in post NAC radical cystectomy samples at Moffitt Cancer Center and correlate them with TD and OS. Methods: Tissue microarrays (TMAs) were constructed from 116 post NAC cystectomy samples. The expressions of Ki-67 were evaluated with immunohistochemistry (IHC) and considered positive if any of the cores per sample were stained positive for Ki-67. The Dako 22C3 assay was used for PD-L1 IHC and the combined positive score of 10 or above was considered positive for PD-L1. Results: The median survival of this cohort of 116 patients was 33.4 months (range: 1.13 -127 months). 40 patients (35%) had TD and 21 patients (18%) achieved pathological complete response. Using Cox regression for OS, positive Ki-67 expression in post NAC radical cystectomy sample was associated with poorer OS (hazard ratio=2.412, 95% CI:1.076-5.408, p=0.033), independent of the pathological N stage. Patients with Ki67/PD-L1 double-negative tumors had a significantly longer median OS of 98.2 months versus 29.9 and 26.9 months in PD-L1-/Ki67+ and PD-L1+/Ki67+ tumors respectively (Log-rank test, p=0.0361). Lack of TD was significantly associated with positive Ki-67 (P<0.001) and positive PD-L1 (p=0.003) in the post NAC samples with a multi-variable logistic regression model. Conclusions: Positive Ki-67 and PD-L1 expressions in post NAC radical cystectomy samples were associated with inferior OS and absence of TD. Adjuvant anti-PD1 therapy either alone or in combination with chemotherapy would be indicated for this subset of patients.