Assessment of PD-L1 Status in Urothelial Cancer.

Since 2016, the immunotherapeutic agents targeting PD-1 and PD-L1 are an integral part in first-line and second-line treatment of advanced or metastatic urothelial cancer. By PD-1 and PD-L1 inhibition with these drugs, the immune system is supposed to regain the capacity to actively kill cancer cells. Meanwhile, PD-L1 assessment is prescribed for patients not being eligible for platinum-based chemotherapy in first-line settings in metastatic disease (for monotherapy with atezolizumab or pembrolizumab) and for patients who are intended to receive adjuvant nivolumab treatment following radical cystectomy. Several challenges which are highlighted in this chapter affect PD-L1 testing in daily routine including availability of representative tissue materials, inter-observer variability, and different available PD-L1 immunohistochemistry assays with different analytical properties.