Additive Duloxetine for Cancer-Related Neuropathic Pain Nonresponsive or Intolerant to Opioid-Pregabalin Therapy: A Randomized Controlled Trial (JORTC-PAL08)

Context: Although opioids and pregabalin are widely used for cancer-related neuropathic pain (CNP), no clinical trials exist to determine which medications are effective when an opioid-pregabalin combination therapy fails. Objectives: We investigated the efficacy of duloxetine for CNP nonresponsive or intolerant to opioid-pregabalin combination therapy. Methods: A multicenter, randomized, double-blind, placebo-controlled trial was performed at 12 specialized palliative care services in Japan. Patients with CNP average pain scores (Brief Pain Inventory [BPI]–Item 5) ≥ 4 in the previous 24 hours and nonresponsive or intolerant to opioid-pregabalin combination therapy were eligible. Patients with chemotherapy-induced peripheral neuropathies were excluded. Patients were administered duloxetine 20 mg/day titrated to 40 mg/day or placebo for 10 days. The primary endpoint was BPI-Item 5 on Day 10. Responder analysis measured proportions of patients with 30% and 50% pain decreases. Results: Seventy patients were enrolled. Complete case analysis revealed mean BPI-Item 5 on Day 10 of 4.03 for Group D vs. 4.88 for Group P (P = 0.053). Baseline observation carried forward analysis revealed mean BPI-Item 5 on Day 10 of 4.06 and 4.91 for Groups D and P, respectively (P = 0.048). Clinically meaningful pain improvement (≥30%) was reported by 44.1% (n = 15) of patients in Group D vs. 18.2% (n = 6) in Group P (P = 0.02); 32.4% (n = 11) vs. 3.0% (n = 1) of patients in Groups D and P, respectively, reported pain reduction ≥ 50% (P = 0.002). Conclusion: Adding duloxetine to opioid-pregabalin therapy might have clinical benefit in alleviating refractory CNP. Further studies are needed to conclude the efficacy of adding duloxetine.