Abstract
Detecting circulating tumour cells (CTCs) is considered as effective and minimally invasive technique to predict the prognosis of patients with metastatic colorectal cancer (CRC), but its clinical validity is still conflicting in patients without metastasis. We performed this meta-analysis to evaluate whether detection of CTCs in the peripheral blood can be used as a prognostic marker for patients with non-metastatic CRC. We performed a comprehensive search of the EMBASE, PubMed, and Web of Science databases (up to September 2016). Meta-analyses were conducted using a random-effects model with the hazard ratio (HR) and 95% confidence interval (95% CI) as the effect measures. Twenty studies including 3,687 patients were eligible for inclusion. Overall analyses demonstrated that the presence of CTCs was significantly associated with aggressive disease progression (HR = 2.57, 95% CI = 1.64–4.02, Pheterogeneity < 0.001, I2 = 81.0%) and reduced disease survival (HR = 2.41, 95% CI = 1.66–3.51, Pheterogeneity = 0.002, I2 = 59.7%). Subgroup analyses further supported the prognostic effect of CTCs based on different subsets, including sampling time, detection method and cancer type. Our findings suggest that detection of CTCs in the peripheral blood has the clinical utility to indicate poor prognosis in patients with non-metastatic CRC.
Highlights
100 (27/27) DFS cut-off values were used
Sampling times seem to influence the prognostic effect of circulating tumour cells (CTCs). van Dalum et al surprisingly found that CTCs detected in the weeks after surgery were not significantly associated with colorectal cancer (CRC) progression whereas CTCs detected 2–3 years after surgery were significantly associated with CRC progression[28]
Twenty-three studies were further removed because of failure to distinguish data of early stage (M0) and metastatic stage (M1) CRC (n = 16), insufficient information to estimate the insufficient information to estimate the hazard ratio (HR) and 95% confidence interval (n = 4), failure to report CTC data of peripheral blood samples (n = 2), or having populations overlapping with another study (n = 1)
Summary
Sampling times seem to influence the prognostic effect of CTCs. van Dalum et al surprisingly found that CTCs detected in the weeks after surgery were not significantly associated with CRC progression whereas CTCs detected 2–3 years after surgery were significantly associated with CRC progression[28]. These discrepancies may result from the small sample size of individual studies, different time points of blood collection, or the use of various detection methods. The outcomes of interest were disease progression (including disease-free survival [DFS] and recurrence-free survival [RFS]) and disease survival (including overall survival [OS], cancer-related survival [CRS] and colon cancer related death [CCRD])
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