Theory based analysis of the effects of decision aids for surgery in early breast cancer: a systematic review

Rationale, aims and objectives: Little is understood about how decision aids achieve their reported effects or their impact on the decision-making process. We aimed to evaluate the quality of decision aids for women choosing surgery for early breast cancer and to examine how their reported effects may reflect the contribution of components suggested by an extended Theory of Planned Behaviour (TPB) and the Common Sense Model of Illness Representations (CSM) to be required for good quality decision-making in this domain. Method: We undertook a systematic review to examine the components of decision aids that influence decision-making processes for women choosing surgery for early breast cancer. The quality and theoretical underpinnings of the decision aids were appraised and reported outcomes meta-analysed. Results: Ten decision aids were obtained; 4 had been evaluated in randomised trials. The quality of the decision aids was similar, with limited evidence of theoretical base. Data linking decision aid components, design, use and outcomes to judge the effects on the decision-making process were inconsistent. Two trials suggested evidence of a reduction in Decision Conflict scores (SMD = -0.35, 95% CI -0.57 to -0.12, p = 0.002). Improvements in knowledge (4 trials) and trends towards breast conservation surgery (3 trials) were not statistically significant. Conclusions: A greater understanding of how decision aids impact on the decision-making process is needed if we are to design improved interventions that are effective on the core aspects of decision-making in this domain.