Background: The aim of this meta-analysis was to systematically update the evidence for mindfulness-based stress reduction (MBSR) and mindfulness-based cognitive therapy (MBCT) in women with breast cancer.

Material and methods: In October 2016, PubMed, Scopus, and Central were searched for randomized controlled trials on MBSR/MBCT in breast cancer patients. The primary outcome was health-related quality of life. Secondary outcomes were fatigue, sleep stress, depression, anxiety, and safety. For each outcome, standardized mean differences (SMD/Hedges' g) and 95% confidence intervals (CI) were calculated. Risk of bias was assessed by the Cochrane risk of bias tool.

Results: The Literature search identified 14 articles on 10 studies that included 1709 participants. The overall risk of bias was unclear, except for risk of low attrition bias and low other bias. Compared to usual care, significant post-intervention effects of MBSR/MBCT were found for health-related quality of life (SMD = .21; 95%CI = [.04-.39]), fatigue (SMD = -.28; 95%CI = [-.43 to -.14]), sleep (SMD = -.23; 95%CI = [-.40 to -.05]), stress (SMD = -.33; 95%CI = [-.61 to -.05]), anxiety (SMD = -.28; 95%CI = [-.39 to -.16]), and depression (SMD = -.34; 95%CI = [-.46 to -.21]). Up to 6 months after baseline effects were significant for: anxiety (SMD = -.28; 95%CI = [-.47 to -.09]) and depression (SMD = -.26; 95%CI = [-.47 to -.04]); and significant for anxiety (SMD = -.21; 95%CI = [-.40 to -.03]) up to 12 months after baseline. Compared to other active interventions, significant effects were only found post-intervention and only for anxiety (SMD = -.45; 95%CI = [-.71 to -.18]) and depression (SMD = -.39; 95%CI = [-.65 to -.14]). However, average effects were all below the threshold of minimal clinically important differences. Effects were robust against potential methodological bias. Adverse events were insufficiently reported.

Conclusions: This meta-analysis revealed evidence for the short-term effectiveness and safety of mindfulness-based interventions in women with breast cancer. However, their clinical relevance remains unclear. Further research is needed.