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. 2015 Mar 27;10(3):e0120996.
doi: 10.1371/journal.pone.0120996. eCollection 2015.

Control group design, contamination and drop-out in exercise oncology trials: a systematic review

Charlotte N Steins Bisschop  1 , Kerry S Courneya  2 , Miranda J Velthuis  3 , Evelyn M Monninkhof  1 , Lee W Jones  4 , Christine Friedenreich  5 , Elsken van der Wall  6 , Petra H M Peeters  1 , Anne M May  1
Affiliations

Control group design, contamination and drop-out in exercise oncology trials: a systematic review

Charlotte N Steins Bisschop et al. PLoS One. .

Abstract

Purpose: Important considerations for exercise trials in cancer patients are contamination and differential drop-out among the control group members that might jeopardize the internal validity. This systematic review provides an overview of different control groups design characteristics of exercise-oncology trials and explores the association with contamination and drop-out rates.

Methods: Randomized controlled exercise-oncology trials from two Cochrane reviews were included. Additionally, a computer-aided search using Medline (Pubmed), Embase and CINAHL was conducted after completion date of the Cochrane reviews. Eligible studies were classified according to three control group design characteristics: the exercise instruction given to controls before start of the study (exercise allowed or not); and the intervention the control group was offered during (any (e.g., education sessions or telephone contacts) or none) or after (any (e.g., cross-over or exercise instruction) or none) the intervention period. Contamination (yes or no) and excess drop-out rates (i.e., drop-out rate of the control group minus the drop-out rate exercise group) were described according to the three design characteristics of the control group and according to the combinations of these three characteristics; so we additionally made subgroups based on combinations of type and timing of instructions received.

Results: 40 exercise-oncology trials were included based on pre-specified eligibility criteria. The lowest contamination (7.1% of studies) and low drop-out rates (excess drop-out rate -4.7±9.2) were found in control groups offered an intervention after the intervention period. When control groups were offered an intervention both during and after the intervention period, contamination (0%) and excess drop-out rates (-10.0±12.8%) were even lower.

Conclusions: Control groups receiving an intervention during and after the study intervention period have lower contamination and drop-out rates. The present findings can be considered when designing future exercise-oncology trials.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Flowchart of included studies.
Exercise oncology trials of the literature search between 19-4-2012 and 16-8-2013 and from two Cochrane reviews updated on 19-4-2012 and 1-6-2012. [1,2].
See this image and copyright information in PMC

References

    1. Cramp F, Byron-Daniel J. Exercise for the management of cancer-related fatigue in adults. Cochrane Database Syst Rev 2012;11: CD006145 10.1002/14651858.CD006145.pub3 - DOI - PMC - PubMed
    1. Fong DY, Ho JW, Hui BP Lee AM, Macfarlane DJ, Leung SS, et al. Physical activity for cancer survivors: meta-analysis of randomised controlled trials. BMJ 2012;344: e70 10.1136/bmj.e70 - DOI - PMC - PubMed
    1. Mishra SI, Scherer RW, Snyder C, Geigle PM, Berlanstein DR, Topaloglu O. Exercise interventions on health-related quality of life for people with cancer during active treatment. Cochrane Database Syst Rev 2012;8: CD008465 10.1002/14651858.CD008465.pub2 - DOI - PMC - PubMed
    1. Courneya KS, Friedenreich CM, Quinney HA, Fields AL, jones LW, Fairey AS. A randomized trial of exercise and quality of life in colorectal cancer survivors. Eur J Cancer Care (Engl) 2003;12(4): 347–357. - PubMed
    1. Courneya KS, Forbes CC, Trinh L, Sellar CM, Friedenreich CM, Reiman T. Patient satisfaction with participation in a randomized exercise trial: effects of randomization and a usual care posttrial exercise program. Clin Trials 2013;10(6): 959–966. 10.1177/1740774513495985 - DOI - PubMed

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