BCL2 gene expression and clinical response. Quantitation of BCL2 performed on CD138-selected BMMCs collected at baseline using droplet digital PCR. BATTing was used to estimate a threshold value for BCL2 (>3) messenger RNA expression that would provide optimum selection of patients likely to have a clinical response (≥PR) vs nonresponse (<PR). Presented are the ORRs (A) and TTP (B) for patients with high BCL2 expression and low BCL2 expression. In panel B, censored events are indicated by a tick mark. PCR, polymerase chain reaction.