Meta-analysis of associations between telomere length and colorectal cancer survival from observational studies.

Background: Telomere length (TL) has been reported to be associated with the risk and survival of several cancers. But it is unclear for the prognostic role of TL in colorectal cancer (CRC). Materials and Methods: Relevant citations were searched and identified using several major online databases through April 2017 which investigated associations between TL and CRC prognosis. We combined summary estimates using hazard ratios (HRs) with 95% confidence interval (CI), which were pooled using a random-effects model. Overall survival (OS) was set as the primary outcome of interest. Results: There are 8 cohort studies encompassing 1622 patients included in the meta-analysis. Pooled estimate indicated that long TL was not significantly associated with patient OS (HR 1.26, 95% CI, 0.76 to 2.08). When we conducted subgroup analyses based on baseline charcteristics, we found that long TL (versus short TL) was significantly associated with poor OS in studies conducted in Europe (n = 4, HR 2.73, 95% CI, 1.65 to 4.52, I-2 = 0), using Southern blot to measure TL (n = 3, HR 2.93, 95% CI, 1.69 to 5.10, I-2 = 0) and patients' age more than 60 years (n = 3, HR 2.65, 95% CI, 1.22 to 5.76, I-2 = 0). We found no significant associations between TL and patient disease-free, recurrence-free or progression-free survival (HR 1.19, 95% CI, 0.45 to 3.15). Conclusions: Current evidence did not provide solid indication that long TL is significantly associated with improved or poor survival for patients with CRC. Further large sample size prospective cohort studies are warranted to determine the true relationship for specific patients.