Preventing adverse events of chemotherapy for gastrointestinal cancer by educating patients about the nocebo effect: a randomized-controlled trial.

ABSTRACT

BACKGROUND: Adverse events of chemotherapy may be caused by pharmacodynamics or psychological factors such as negative expectations, which constitute nocebo effects. In a randomized controlled trial, we examined whether educating patients about the nocebo effect is efficacious in reducing the intensity of self-reported adverse events. METHODS: In this proof-of-concept study, N = 100 outpatients (mean age 60.2 years, 65% male, 54% UICC tumour stage IV) starting first-line, de novo chemotherapy for gastrointestinal cancers were randomized 11 to a nocebo education (n = 49) or an attention control group (n = 51). Our primary outcome was patient-rated intensity of four chemotherapy-specific and three non-specific adverse events (rated on 11-point Likert scales) at 10-days and 12-weeks after the first course of chemotherapy. Secondary outcomes included perceived control of adverse events and tendency to misattribute symptoms. RESULTS: General linear models indicated that intensity of adverse events differed at 12-weeks after the first course of chemotherapy (mean difference 4.04, 95% CI [0.72, 7.36], p = .02, d = 0.48), with lower levels in the nocebo education group. This was attributable to less non-specific adverse events (mean difference 0.39, 95% CI [0.04, 0.73], p = .03, d = 0.44) and a trend towards less specific adverse events in the nocebo education group (mean difference 0.36, 95% CI [- 0.02, 0.74], p = .07, d = 0.37). We found no difference in adverse events at 10-days follow-up, perceived control of adverse events, or tendency to misattribute non-specific symptoms to the chemotherapy. CONCLUSIONS: This study provides first proof-of-concept evidence for the efficacy of a brief information session in preventing adverse events of chemotherapy. However, results regarding patient-reported outcomes cannot rule out response biases. Informing patients about the nocebo effect may be an innovative and clinically feasible intervention for reducing the burden of adverse events. TRIAL REGISTRATION Retrospectively registered on March 27, 2018 to the German Clinical Trial Register (ID DRKS00009501).