In the recently initiated Phase 2 randomized trial investigating the combination of maintenance atezolizumab with talazoparib versus atezolizumab alone for patients with SLFN11-positive extensive-stage SCLC (ES-SCLC) (SWOG1929, NCT04334941), SLFN11 expression by IHC is clinically feasible because it can be easily assessed as positive (H score > 1) or negative, and has been found to be positive in ~50% of ES-SCLC [51]. The gene discussed is SLFN11; the disease is small cell lung carcinoma.