Paller CJ, Piana D, Eshleman JR, et al. - Through a retrospective examination of 96 men with metastatic castration-resistant prostate cancer (mCRPC) who underwent an assessment at medical oncology clinics, researchers carried out serial measurements of prostate-specific membrane antigen (PSMA) expression on circulating tumor cells (CTCs) in order to assess patterns of longitudinal PSMA dynamics over the course of multiple sequential therapies. A total of 15 had ≥ two sequential therapies and evaluable CTC samples, ≥ one expressing PSMA (PSMA+). Collectively, during a median follow-up of 18 months, 54 PSMA status assessments were conducted in the regards of 48 therapies. The PSMA signal was detected (“positive”) and could not be detected (“negative”) in 11 and 4 of 15, respectively, at baseline. The baseline collection corresponded with a variation in treatment in all but two individuals. In all 4/4 PSMA-negative patients and 8 of 11 PSMA-positive patients, PSMA raises were detected on the following evaluation. In a patient treated with 177Lu-PSMA-617, PSMA significantly diminished. In 7 of 8 of the treatment periods where PSMA decreased, serum prostate-specific antigen (PSA) drops were observed. Therefore, PSMA expression in CTCs was concluded as a dynamic marker. PSMA transcript declines seemed to be correlated with concurrent reductions in serum PSA. Moreover, for mCRPC, sequential CTC sampling could render a noninvasive response evaluation to systemic treatment.