The relationship between anticipated response and subsequent experience of cancer treatment-related side effects: A meta-analysis comparing effects before and after treatment exposure

Objective: To review the evidence for a systematic relationship between cancer patients' pre-treatment expectations (anticipated side effects) and subsequent experience of treatment-related side effects, and to compare this relationship in patients with no prior treatment experience (cognitive expectations) and with some prior treatment experience (conditioned response). Methods: A total of 12,952 citations were identified through a comprehensive search of the literature published on or before November 2016 and screened against inclusion criteria. Studies were eligible if they included participants undergoing curative treatment for cancer, measured a treatment side effect, examined the relationship between anticipation and experience of side effects, and reported quantitative data. Results: Thirty-one studies were included in the review and meta-analysis (total N = 5069). The side effects examined were nausea (anticipatory and post-treatment), vomiting, fatigue, pain, problems with concentration, and skin reactions. Meta-analyses indicated positive associations between anticipation and subsequent experience for all included side effects in patients with no prior treatment exposure (r = 0.153-0.431). Stronger associations were found for all included side effects in patients with previous treatment experience (r = 0.211-0.476), except for fatigue (r = 0.266) and pain (r = 0.235). No significant differences were found when overall effect sizes for patients with and without prior treatment exposure were compared for each side effect, except for anticipatory nausea (p = 0.012). Conclusion: These results may have implications for future interventions that target patients' expectations of cancer treatment-related side effects. Future research could explore patient reports of messages received about likely treatment effects both before and during treatment.