Role of circulating tumor cells in patients with metastatic clear-cell renal cell carcinoma

Purpose: Circulating tumor cells (CTC) have been demonstrated to have prognostic and predictive role in certain human cancers. However, studies exploring their role in metastatic renal cell carcinoma (mRCC) are scarce. We aimed to evaluate the prognostic and predictive role of CTC in mRCC. Materials and methods: In this prospective study, 35 patients with mRCC were analyzed for the presence of CTC before starting tyrosine kinase inhibitors (TKI). Progression-free and overall survival rates were estimated using the Kaplan-Meier curves and log-rank test. The prediction to TKI therapy was calculated with the response to treatment determined by standard imaging techniques. Results: Outcomes were assessed according to the CTC positivity at baseline, before the patients started TKI for mRCC. At a mean follow-up of 12.4 ± 4.1 months, disease progression was noted in 17 patients (48.6%) including 8 deaths (22.9%). CTC positive patients had a significantly lower progression-free survival rate (12.5% vs. 64.1%, respectively; P = 0.009) but not in the overall survival rate (75% vs. 76.3%, respectively; P = 0.88) in the Kaplan–Meier estimation curves. CTC positivity at baseline significantly predicted a poorer response to TKI (87.5% vs. 37.1%, P = 0.01). The multivariate Cox proportional hazards analysis showed that CTC at baseline was the most significant predictor of progression-free survival (hazard ratio 4.17, 95% confidence interval 1.41–11.99, P = 0.01). Conclusions: Baseline CTC detection can be an important prognostic factor of progression-free survival and significant predictor of poor response to TKI in patients with metastatic RCC.