Purpose: Cancer-related fatigue (CRF) is a common symptom among patients with cancer. The efficacy of placebo, however, was never the main objective of any meta-analysis. Predicting the efficacy of placebo may facilitate researchers in designing future clinical trials for the treatment of CRF.
Methods: We performed a systematic review searching for prospective clinical trials comparing any treatment versus placebo for the treatment of CRF. We included studies that enrolled patients with any primary site of neoplasia and any stage of cancer. We excluded all studies that assessed fatigue related to any treatment. The primary endpoint of this study is the mean effect of placebo on fatigue according to the Functional Assessment of Chronic Illness (FACIT-F) and Brief Fatigue Inventory (BFI) scales. The secondary endpoint was the proportion of patients who reported improvement in fatigue (response rate).
Results: We found 520 studies, and 29 studies with 3758 participants were included in the meta-analysis. Placebo had a mean effect of + 4.88 (95%CI + 2.45 to + 7.29) using the FACIT-F scale, although it was statistically worse than the interventions studied (p = 0.005). Using the BFI scale, placebo had an average effect of + 0.64 (95%CI + 0.02 to + 1.30), although it was also worse than the other interventions studied (p = 0.002). In terms of the response rate, 29% (95%CI 25-32%) of patients taking a placebo reported a significant improvement in CRF compared with 36% of patients treated with other interventions (p = 0.030).
Conclusions: Placebo treatments had a significant effect on CRF, and predicting these effects may help design future studies for CRF.
Keywords: Cancer; Fatigue; Palliative care; Placebo effect.