title: Single-agent purine analogues for the treatment of chronic lymphocytic leukaemia: a systematic review and meta-analysis.
abstract: BACKGROUND
  Recent trials suggest improved response rates for purine analogues compared to alkylator-based regimens in the treatment of B-CLL. However, none was able to show a survival advantage. Thus, a systematic Cochrane review may be able to further define the role of purine analogues in the first-line treatment of B-CLL.
  
  
  METHODS
  Randomized controlled trials comparing single-agent purine analogues with alkylator-based regimens were included. Medical databases (Cochrane Library, MEDLINE, EMBASE), conference proceedings and trial registers were searched. We included full-text and abstract publications as well as unpublished data. Relative risks (RR) and hazard ratios (HR) were calculated under a fixed-effects model, clinical and statistical heterogeneity was examined with sensitivity analyses and meta-regression. If applicable, numbers needed to treat or harm (NNT, NNH) were also determined.
  
  
  RESULTS
  Five trials with 1838 randomized patients were included. Importantly, four trials had a cross-over design. There was a trend for improved overall survival for patients receiving purine analogues as initial therapy but statistical significance was just not reached (HR 0.89 [95% CI 0.78-1.01]). The RR for achieving an overall (RR 1.22 [95% CI 1.13-1.31]; NNT 8 [95% CI 6-13]) and complete response (RR 1.94 [95% CI 1.65-2.28]; NNT 6 [5-8]) was significantly improved, resulting in a longer progression-free survival (HR 0.70 [95% CI 0.61-0.82]). Incidence of grade III/IV infections (RR 1.83 [95% CI 1.30-2.58]; NNH 20 [95% CI 12.5-50]) and haemolytic anaemia (RR 3.36 [95% CI 1.27-8.91]; NNH 21 [95% CI 6-185]) was significantly higher in patients receiving purine analogues.
  
  
  CONCLUSIONS
  Despite significantly increased response rates and longer progression-free survival with purine analogues as first-line therapy, we were not able to detect a statistically significant improvement of overall survival compared to alkylator-based regimens. Furthermore, the use of purine analogues augments the risk for grade III/IV infections and haemolytic anaemia.
authors.affiliation: Innsbruck Medical University, Division of Hematology and Oncology, Anichstrasse 35, A-6020 Innsbruck, Austria. michael.steurer@uibk.ac.at
authors.forename: Michael
authors.initials: M
authors.lastname: Steurer
authors.forename: Georg
authors.initials: G
authors.lastname: Pall
authors.forename: Sue
authors.initials: S
authors.lastname: Richards
authors.forename: Guido
authors.initials: G
authors.lastname: Schwarzer
authors.forename: Julia
authors.initials: J
authors.lastname: Bohlius
authors.forename: Richard
authors.initials: R
authors.lastname: Greil
mesh_terms: D000743:Anemia, Hemolytic / Q000139:chemically induced; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017338:Cladribine / Q000627:therapeutic use; D018572:Disease-Free Survival; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy*; D015649:Pentostatin / Q000627:therapeutic use; D016032:Randomized Controlled Trials as Topic; D016019:Survival Analysis; D016896:Treatment Outcome; D014740:Vidarabine / Q000031:analogs & derivatives / Q000627:therapeutic use
chemical_list: D000970:Antineoplastic Agents; D015649:Pentostatin; D017338:Cladribine; D014740:Vidarabine; C024352:fludarabine