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: N = 49 and n = 51 patients (mean age: 60.2 years, 65% male, 54% UICC tumour stage IV) with newly-diagnosed gastrointestinal cancer were allocated to a nocebo education and attention control group, respectively. Results: GLM with adjustments for tumour staging and distress indicated that intensity of adverse events differed at 12-weeks after onset 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. Of these,). 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).