Background: Meta-analyses of randomized controlled trials (RCTs) have shown that exercise has beneficial effects on quality of life (QoL) in patients with breast cancer. However, these effects were often small. Blinding in an exercise trial is not possible, which has the possible disadvantage of difficult accrual, drop-out after randomization to control and contamination between study groups (controls adopting the behaviour of the intervention group). The cohort multiple randomized controlled trial (cmRCT) is an alternative for conventional RCTs and has the potential to overcome these disadvantages.
Methods: This cmRCT will be performed within the Utrecht cohort for Multiple BREast cancer intervention studies and Long-term evaLuAtion (UMBRELLA). Patients with breast cancer who visit the radiotherapy department of the University Medical Center Utrecht are asked to participate in UMBRELLA. Patients give consent for collection of medical information, providing patient-reported outcomes through regular questionnaires and randomization into future intervention studies. Patients who fulfill the UMBRELLA Fit study eligibility criteria (12 to 18 months post inclusion in UMBRELLA, low physical activity level) will be randomly allocated to the intervention or control group (1:1 ratio). Patients randomized to the intervention group will be offered a 12-week exercise programme. The control group will not be informed. Regular cohort measurements will be used for outcome assessment. Feasiblity (including participation, contamination, generalizability and retention) of the cmRCT design and effects of the intervention on QoL will be evaluated.
Discussion: We will examine the feasibility of the cmRCT design in exercise-oncology research and compare this with conventional RCTs. Furthermore, the effectiveness of an exercise intervention on the QoL of patients with breast cancer in the short term (6 months) and long term (24 months) will be studied.
Trial registration: Netherlands Trial Register, NTR5482/NL.52062.041.15 . Retrospectively registered on 7 December 2015.
Keywords: Breast cancer; Cohort multiple randomized controlled trial; Exercise; Physical activity; Quality of life.