(UroToday.com) Among men with metastatic castration-resistant prostate cancer (mCRPC), there is a subset who develop aggressive variant or neuroendocrine/small-cell-like (NE/SC) tumors.  These men display particularly poor outcomes. Although a field of active investigation of underlying mechanisms of development, effective therapies remain a clear unmet clinical need.  The current standard of care is typically platinum- or taxane-based chemotherapies.  The investigators conducted a single arm, two-stage phase II trial (PICK-NEPC1) to evaluate whether men these tumors respond to treatment with avelumab, a PD-L1 inhibitor.