Topical Traditional Chinese Medicines for Cancer Pain: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND AND OBJECTIVES: Safe and effective management of cancer-related pain is a worldwide challenge. In the search for treatment options, natural products used in Chinese herbal medicines (CHMs) have received attention in clinical studies for their effects on cancer-related pain. The objective of this systematic review is to evaluate the clinical evidence for topically applied CHMs as adjunctive treatments for cancer pain management. METHODS: Nine biomedical databases and 4 clinical trial registries were searched for randomized-controlled trials (RCTs) that reported measures of pain and/or quality of life. Risk of bias was assessed using the Cochrane tool. Meta-analysis employed mean difference (MD) with 95% confidence intervals (random effects). RESULTS: Twenty (20) RCTs (1636 participants) met the inclusion criteria. Meta-analyses were grouped based on the comparisons and outcome measures. For pain intensity, there was a greater reduction in the topical CHM group versus placebo (MD −0.72 [−1.04, −0.40]), no difference when compared to tramadol (MD −0.15 [−0.38, 0.08]), and a greater reduction when topical CHMs were combined with conventional analgesic medications (MD −0.67 [−0.93, −0.40]). Analgesic onset time was reduced in the CHM group compared to tramadol (MD −26.02 [−27.57, −24.47] minutes), and for CHMs combined with conventional medications (MD −19.17 [−21.83, −16.52] minutes). When CHMs were combined with analgesic medications, improvements were found for duration of analgesia (MD 1.65 [0.78, 2.51] hours), analgesic maintenance dose (MD −31.72 [−50.43, −13.01] milligrams/day), and quality of life. CONCLUSION: Addition of topical CHMs to conventional analgesic medications was associated with improved outcomes for pain intensity, some other pain-related outcomes, and measures of quality of life. Limitations included methodological issues in some studies and considerable heterogeneity in some pooled results.