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Abstract
Introduction: Taxane-induced peripheral neuropathy (TIPN) is experienced by most patients with breast cancer, and there is no efficacious treatment. In pre-clinical studies, co-administration of two constituents of cannabis, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), synergistically reduces TIPN.
Materials and Methods: The goal of this 8-week, double-blind, randomized pilot study, conducted from 2019 to 2021, was to test the feasibility and tolerability of oral cannabis (100 mg CBD: 5 mg THC, TID) relative to placebo on pain resulting from TIPN. Participants with painful TIPN completed daily questionnaires online about their pain, sleep, and medication use, and weekly questionnaires on neuropathy.
Results: All participants (12 women; 51 ± 6 years) randomized to placebo (n = 6) or active (n = 6) cannabis capsules completed the trial. Participants in both medication groups requested dose reductions (mean ± SEM capsules/day: placebo: 2.4 ± 0.4; active: 2.0 ± 0.4). In a preliminary evaluation of efficacy, measures of pain, pain interference, sleep, and functional well-being significantly improved over time (p < 0.03), but participants receiving cannabis had significantly higher ratings of neuropathy at each week (p < 0.035) and lower ratings of functional well-being in the last 3 weeks of treatment compared with participants receiving placebo (p < 0.02). Similarly, cannabis significantly worsened ratings of sleep and pain interference relative to placebo (p < 0.05).
Discussion: This study demonstrates that: (1) double-blind, placebo-controlled testing of cannabis capsules in this dose range is feasible and well tolerated in women with TIPN and (2) ratings of pain, neuropathy, and well-being significantly improved over 8 weeks, but cannabis significantly worsened several endpoints relative to placebo. These findings highlight the necessity of placebo control when assessing the therapeutic utility of cannabis. Although there was no signal of efficacy herein, a fully powered study testing a range of cannabis doses for TIPN is warranted, given its impact on most patients with breast cancer, promising pre-clinical data, and the widespread use of cannabis among patients with cancer.