**4.8. Other cancers**

significantly associated with shorter disease free survival (DFS, HR 4.62, 95% CI 2.51–8.52).

Early in 2004, Vona et al. have reported that the presence (*P* = 0.01) and number (*P* = 0.02) of CTCs and microemboli (CTMs) were significantly associated with a shorter survival [161]. Fan et al. [297] reported a meta‐analysis consisting of 23 trials and found that CTC positivity was significantly associated with RFS (HR 3.03, 95% CI: [1.89–4.86]; *P* < 0.00001) and overall survival (OS) (HR 2.45, 95% CI: [1.73–3.48]; *P* < 0.00001). CTC positivity were also significantly associ‐ ated with TNM Stage (RR 1.30, 95% CI: [1.02–1.65]; *P* = 0.03), Tumor size (RR 1.36, 95% CI: [1.09–1.69]; *P* = 0.006), Vascular invasion (RR 1.99, 95% CI: [1.43–2.77]; *P* < 0.0001), Portal vein tumor thrombus (RR 1.73, 95% CI: [1.42–2.11]; *P* = 0.0001), Serum alpha‐fetoprotein (AFP) level (RR 2.05; *P* = 0.01) [297]. Sun et al. found that Stem cell‐like phenotypes are observed in EpCAM <sup>+</sup> CTCs, and a preoperative CTCs of ≥2 is a novel predictor for tumor recurrence in hepatocel‐ lular carcinoma (HCC) patients after surgery, especially in patient subgroups with AFP levels of ≤400 ng/ml or low tumor recurrence risk. EpCAM+ CTCs could serve as a real‐time parameter for monitoring treatment response and a therapeutic target in HCC recurrence [137]. The prognostic value of overall survival of CTCs in HCC patients has been also revealed

Rink et al. (2012) found that using CellSearch™, CTC were detected in 23 of 100 patients (23%) with nonmetastatic urothelial carcinoma of urinary bladder. CTC‐positive patients had significantly higher risks of disease recurrence and cancer‐specific and overall mortality (*P* values ≤ 0.001). After adjusting for effects of standard clinicopathologic features, CTC posi‐ tivity remained an independent predictor for all end points (hazard ratios: 4.6, 5.2, and 3.5, respectively; *P* values ≤ 0.003). HER2 positivity was found in 3 of 22 patients (14%). There was concordance between CTC, primary tumors, and lymph node metastases in all CTC‐positive

Conventionally, melanoma cells lack of cytokeratin or EpCAM expression and CTCs by definition are very difficult to identify. However, investigators broke through the strait by combination with CTCs plus cfDNA. Salvianti et al. [299] enrolled 84 melanoma patients and 68 healthy controls for CTC and cell‐free DNA (cfDNA) testing to assess the diagnostic performance of a tumor‐related methylated cfDNA marker in melanoma patients and to compare this parameter with the presence of CTCs. The percentage of cases with methylated RASSF1A promoter in cfDNA was significantly higher in each class of melanoma patients (in situ, invasive and metastatic) than in healthy subjects (*P* < 0.001). The concentration of RASSF1A methylated cfDNA in the subjects with a detectable quantity of methylated alleles was significantly higher in melanoma patients than in controls. When the CTCs plus RASSF1A cfDNA are jointly considered, a higher sensitivity of the detection of positive cases in invasive

The presence of CTC indicates a worse DFS.

**4.5. Liver cancer**

164 Tumor Metastasis

[298].

cases (100%).

**4.6. Genitourinary tract cancer**

**4.7. Skin cancer and melanoma**

For ovarian cancer, Romero‐Laorden et al. [302] performed a meta‐analysis enrolling 14 studies. Results showed the presence of CTCs and DTCs is associated with adverse clinicopa‐ thological characteristics and poor clinical outcomes in ovarian cancer patients. They noticed that different CTC number obtained by different devices could not be compared. Using size‐ based isolation strategy (MetaCell®) in 118 ovarian cancer patients, CTCs might have add‐on values on current staging system and the cells could be cultivated after isolation [303, 304]. Furthermore, in another meta‐analysis, eight studies of 1184 ovarian cancer patients were included in the final analysis. In the PB group, it showed that patients with positive CTCs had significantly shorter overall survival (OS) and disease‐free survival (DFS) than patients with negative CTCs (HR, 2.09; CI, 1.13–3.88 and HR, 1.72; CI, 1.32–2.25, respectively). The same result was shown with DTCs in the BM group (HR, 1.61; CI, 1.27–2.04 and HR, 1.44; CI, 1.15– 1.80, respectively) [305].

For carcinoma of unknown primary (CUP), Matthew et al. [306] used a real‐time, single‐cell multiplex immunophenotyping of CTCs to inform diagnosis of tissue of origin in CUP patients. CellSearch™ plus multiplexed Q‐dot or DyLight conjugated antibodies were used for cyto‐ keratin 7 (CK7), cytokeratin 20 (CK20), thyroid transcription factor 1 (TTF‐1), estrogen receptor (ER), or prostate‐specific antigen (PSA) expression. The feasibility of staining multiple markers in CTCs presented in this work suggested CTCs could possibly have a non‐inferior role as that of cancer tissues in diagnostics.
