Meta-analysis of the prognostic value of circulating tumor cells detected with the CellSearch System in colorectal cancer

Background: The prognostic value of circulating tumor cells (CTCs) detected with the CellSearch System in patients with colorectal cancer (CRC) is controversial. The aim of our meta-analysis was to evaluate whether the detection of CTCs in the peripheral blood with the standardized CellSearch System has prognostic utility for patients with CRC. Methods: The PubMed, Science Citation Index, Cochrane Database, Embase, and the references in relevant studies were systematically searched (up to December, 2014). No search restrictions were imposed. Our meta-analysis was performed in Stata software, version 12.0 (2011) (Stata Corp, College Station, TX, USA), with the odds ratio (OR), risk ratio (RR), hazard ratio (HR), and 95% confidence interval (95% CI) as the effect measures. Subgroup and sensitivity analyses were also conducted. Results: Eleven studies containing 1847 patients with CRC were analyzed. There was a significantly higher incidence of CTCs in the metastasis-positive group than in the metastasis-negative group (OR = 4.06, 95% CI [1.74, 9.50], P < 0.01, I-2 = 0%). For hepatic metastasis, a type of metastasis, a higher incidence of CTCs was observed in the hepatic-metastasis-positive group than in the -negative group (OR = 2.61, 95% CI [1.73, 3.96], P < 0.01, I-2 = 0%). The presence of CTCs was significantly related to overall survival (HR = 2.00, 95% CI [1.49, 2.69], P < 0.01, I-2 = 67.1%) and progression-free survival (HR = 1.80, 95% CI [1.52, 2.13], P < 0.01, I-2 = 43.9%) of patients with CRC, regardless of the sampling time. The response rate for the CTC+groups was significantly lower than that for the CTC-groups at baseline and during treatment (baseline: 33% versus 39%, RR = 0.79, 95% CI [0.63, 0.99], P = 0.04, I-2 = 7.0%; during treatment: 17% versus 46%, RR = 0.41, 95% CI [0.22, 0.77], P = 0.01, I-2 = 0.0%;). Conclusions: Our meta-analysis indicates that the detection of CTCs in the peripheral blood with the CellSearch System has prognostic utility for patients with CRC.