Are mind-body therapies effective for relieving cancer-related pain in adults? A systematic review and meta-analysis

Objective To assess whether mind-body therapies are effective for relieving cancer-related pain in adults, since at least one-third of adults with cancer are affected by moderate or severe pain. Methods We searched for all randomized or quasi-randomized controlled trials that included adults (>= 18 years) with cancer-related pain who were treated with mind-body therapies (mindfulness, hypnosis, yoga, guided imagery, and progressive muscle relaxation) in MEDLINE, Embase, CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL), Science Citation Index, Web of Science, trials registers, and reference lists. The primary outcome was pain intensity. We calculated the standardized mean differences and 95% confidence intervals (CIs) and assessed the risk of bias. Results We identified 40 primary studies involving a total of 3569 participants. The meta-analysis included 24 studies (2404 participants) and showed a significant effect of -0.39 (95% CI -0.62 to -0.16) with considerable heterogeneity (I-2 = 86.3%, p < 0.001). After we excluded four "outlier" studies in sensitivity analyses, the effect size remained significant but weaker. There was a high risk of bias in all studies, for example, performance bias due to lack of participant blinding. Patients in multiple settings were included but many studies were of low quality. Conclusions Mind-body therapies may be effective in improving cancer pain, but the quality of the evidence is low. There is a need for further high-quality clinical trials.