Comparative Efficacy of Different Exercise Therapies for Cardiorespiratory Fitness in Breast Cancer Survivors: A Systematic Review and Bayesian Network Meta-analysis.

Background: Breast cancer survivors undergoing cancer therapy are at an increased risk of developing cardiovascular disease. As a result, exercise has become a research hotspot in preventing decreased cardiorespiratory fitness (CRF) in breast cancer survivors. However, there is no consensus on which type of exercise is the most effective in improving cardiorespiratory function of breast cancer survivors. Therefore, this network meta-analysis (NMA) aims to compare the effects of different exercise therapies and explore the possible optimal choice to improve CRF in breast cancer survivors.

Methods: A systematic search was conducted in EMBASE, the Cochrane Library, PubMed, Web of Science, and CINAHL to identify relevant randomized controlled trials (RCTs). The analysis was then performed using R Version 3.5.1 and GEMTC software, employing a NMA with a Bayesian random effects model to synthesize the comparative effectiveness of different exercise schemes on CRF in breast cancer survivors. A network graph was constructed to visualize the relative relationship for each exercise therapy in relation to the others. Direct and mixed evidence were estimated with mean difference (MD) and 95% credible interval (CrI) and presented in a forest plot and league table. The cumulative rank plot was created and surface under the cumulative ranking (SUCRA) scores were calculated to rank the exercise schemes. Additionally, a network meta-regression analysis was conducted to evaluate if the different timing of exercise (during and after cancer treatment) has an influence on the effects found in this NMA.

Results: The analysis included 41 eligible RCTs and a total of 2606 participants. The results indicated that moderate-intensity continuous aerobic training (MICT; MD: 1.6, 95%Cr 0.13 to 3.1), moderate-to-vigorous aerobic exercise (M-V; MD: 3.4, 95%CrI 1.9 to 5.0), high-intensity interval training (HIIT; MD: 2.9, 95%CrI 1.2 to 4.6), and moderate-to-vigorous aerobic training combined with resistance exercise (M-V + RE; MD: 4.3, 95%CrI 2.5 to 6.1) had better efficacy than usual care on CRF. M-V + RE was significantly better than MICT (MD: 2.7, 95%CrI 0.4 to 5.0). Amongst 12 exercise interventions, M-V + RE was shown to have the highest-ranking probability of being the best treatment (SUCRA: 88.15%). No statistical difference was observed for the relative effects of different timing of exercise for CRF improvement compared to usual care in network meta-regression analyses.

Conclusions: This NMA suggests MICT, M-V, HIIT, and M-V + RE as available options for improving CRF in breast cancer survivors, and M-V + RE is likely to be the optimal choice for improving CRF. Further high-quality studies are needed to continue to confirm the role of M-V + RE in improving CRF among breast cancer survivors.