title: The Association between Telomere Length and Cancer Prognosis: Evidence from a Meta-Analysis.
abstract: BACKGROUND
  Telomeres are essential for chromosomal integrity and stability. Shortened telomere length (TL) has been associated with risk of cancers and aging-related diseases. Several studies have explored associations between TL and cancer prognosis, but the results are conflicting.
  
  
  METHODS
  Prospective studies on the relationship between TL and cancer survival were identified by a search of PubMed up to May 25, 2015. There were no restrictions on the cancer type or DNA source. The quality of the included studies was assessed using the Newcastle-Ottawa Scale. Meta-analysis approaches were conducted to determine pooled relative risks and 95% confidence intervals.
  
  
  RESULTS
  Thirty-three articles containing forty-five independent studies were ultimately involved in our meta-analysis, of which twenty-seven were about overall cancer survival and eighteen were about cancer progression. Short TL was associated with increased cancer mortality risk (RR = 1.30, 95%CI: 1.06-1.59) and poor cancer progression (RR = 1.44, 95%CI: 1.10-1.88), both with high levels of heterogeneity (I2 = 83.5%, P = 0.012for overall survival and I2 = 75.4%, P = 0.008 for progression). TL was an independent predictor of overall cancer survival and progression in chronic lymphocytic leukemia. Besides, short telomeres were also associated with increased colorectal cancer mortality and decreased overall survival of esophageal cancer, but not in other cancers. Cancer progression was associated with TL in Asian and America populations and short TL predicted poor cancer survival in older populations. Compared with tumor tissue cells, TL in blood lymphocyte cells was better for prediction. In addition, the associations remained significant when restricted to studies with adjustments for age, with larger sample sizes, measuring TL using southern blotting or estimating risk effects by hazard ratios.
  
  
  CONCLUSIONS
  Short TL demonstrated a significant association with poor cancer survival, suggesting the potential prognostic significance of TL. Additional large well-designed studies are needed to confirm our findings.
authors.affiliation: Institute of Orthopedics, the First Affiliated Hospital of Chinese People's Liberation Army General Hospital, Beijing, China; Medical School of Chinese People's Liberation Army, Beijing, China.
authors.forename: Chunli
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Laboratory Medicine, No 161 Hospital of People's Liberation Army, Wuhan, China.
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Chen
authors.affiliation: Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Li
authors.affiliation: Institute of Orthopedics, the First Affiliated Hospital of Chinese People's Liberation Army General Hospital, Beijing, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of General Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.affiliation: Institute of Orthopedics, the First Affiliated Hospital of Chinese People's Liberation Army General Hospital, Beijing, China; Medical School of Chinese People's Liberation Army, Beijing, China.
authors.forename: Shuxun
authors.initials: S
authors.lastname: Hou
mesh_terms: D018450:Disease Progression; D006801:Humans; D009369:Neoplasms / Q000175:diagnosis* / Q000473:pathology; D011379:Prognosis; D017594:Publication Bias; D016019:Survival Analysis; D059505:Telomere Homeostasis