Programmed cell death ligand 1 (PD-L1) inhibitors are commonly used in treating advanced-stage urothelial carcinoma (UC). Therefore, this study evaluated the relationship between PD-L1 expression in circulating tumor cells (CTCs) and treatment response to PD-L1 inhibitors using blood samples collected from patients with UC (n = 23). Subsequently, PD-L1 expression and its clinical correlation were analyzed. All patients had CTCs before PD-L1 inhibitory treatment, of which 15 had PD-L1-positive CTCs. However, PD-L1-positive expression in CTCs was not correlated with PD-L1 expression in tumor biopsy samples. Patients with PD-L1-positive CTCs had better disease control (DC) rates than those without PD-L1-positive CTCs. Moreover, changes in the proportion of PD-L1-positive CTCs were associated with disease outcomes. Furthermore, the PD-L1-positive CTC count in 9 of 11 patients who achieved DC had significantly decreased (p = 0.01). In four patients with progressive disease, this was higher or did not change. PD-L1-positive CTCs at baseline could be used as a biomarker to identify patients suitable for PD-L1 blockade therapy. Dynamic changes in PD-L1-positive CTCs during the course of treatment are predictive factors of immunotherapy response and prognostic factors of disease control. Hence, PD-L1-positive CTCs could be employed as a real-time molecular biomarker for individualized immunotherapy.

Background: This study aimed to investigate the presence of circulating tumor cells (CTCs) in patients with penile squamous cell carcinoma (PSCC). Methods: CTCs were isolated from 14 patients with PSCC, 6 patients with balanoposthitis, and 6 healthy individuals. CTCs were enriched based on cell surface markers and filtered through the IsoFlux device, followed by identification according to cell morphology and immunofluorescence studies. Results: CTCs were found in all PSCC blood samples but not in balanoposthitis samples and samples from healthy individuals. Immunofluorescence studies confirmed the tumor origin. When the patients with PSCC were stratified according to metastatic inguinal lymph node status, a statistically significant difference was observed in the number of detected CTCs. Conclusion: Our study showed that CTCs in PSCC may represent a valuable marker for differentiating PSCC from other tumors. Based on the correlation with some clinical parameters, CTC analysis is possibly relevant for noninvasive monitoring of disease progression and prognosis. The results also suggested a potential role of CTCs in preventing overtreatment, such as inguinal lymph node dissection.