The PD-1/PD-L1 pathway in advanced prostate cancer—have we milked this cow?

We would like to thank Dr. Fay and Dr. Antonarakis for their insightful comments on immunotherapy (IO) in advanced prostate cancer and specifically their commentary on the recently published KEYNOTE-028 study on the use of pembrolizumab in programmed cell death protein-1 ligand (PD-L1) positive metastatic castrate resistant prostate cancer (mCRPC) (1). As described by the authors, monotherapy with checkpoint inhibitors has not demonstrated the dramatic response rates in mCRPC that were shown in other cancer types such as melanoma and non-small cell lung cancer (NSCLC).