Eight RCTs (768 participants, sample size range 30 to 250) were included in the meta-analysis. Overall trial quality was considered to be moderate. One trial reported the method of randomisation. All trials reported allocation concealment. Blinding or use of placebo were not present in any of the trials. Loss to follow-up was unknown in most trials.
Melatonin therapy was associated with significantly increased complete or partial tumour remission (RR 1.95, 95% CI 1.49 to 2.54; eight trials; Ι²=0%), and survival at one year (RR 1.90, 95% CI 1.28 to 2.83; five trials; Ι²=61.9% indicating significant heterogeneity).
Melatonin therapy was associated with significantly fewer side effects for thrombocytopenia (RR 0.13, 95% CI 0.06 to 0.28; five trials; Ι²=0%), neurotoxicity (RR 0.19, 95% CI 0.09 to 0.40; five trials; Ι²=0%), and fatigue (RR 0.37, 95% CI 0.28 to 0.48; five trials; Ι²=0%).