Two distinct molecular clusters in circulating tumor cells from patients with metastatic prostate cancer. Hierarchical clustering of gene expression data of 11 genes from 99 patients with prostate cancer identified two distinct clusters (cluster 1: C1 and cluster 2: C2). Serum PSA (ng/mL), prostate cancer type, treatment with ARSI or chemotherapy in CRPC setting, sites of metastases at time of blood draw, and serum PSA at time of blood draw are indicated. X indicates presence of metastases at indicted site. AR, androgen receptor; ARSI, androgen receptor signaling inhibitor; AR-V, androgen receptor splice variant; CRPC, castration-resistant prostate cancer; CSPC, castration-sensitive prostate cancer; LN, lymph node; NEPC, neuroendocrine prostate cancer; PSA, prostate-specific antigen.