Long-term low-dose morphine for patients with moderate cancer pain is predominant factor effecting clinically meaningful pain reduction

Purpose Patients with cancer often experience pain that affects their daily activities and quality of life. The analgesic ladder recommended by the World Health Organization has proved insufficient for many, and its scientific basis has been questioned. This retrospective study investigated factors related to adherence to long-term opioid therapy for patients with moderate cancer pain, including an evaluation of low-dose morphine relative to tramadol. Methods Clinical data were collected of patients with moderate cancer pain ( n = 353) who received either low-dose morphine or tramadol and were followed for ≥ 27 weeks. Factors related to regime adherence were investigated, including the analgesia type, cancer therapy (antitumor therapy or palliative care), pain type (nociceptive, neuropathic, or mixed), and living distance to the hospital. Factors related to clinically meaningful pain reduction (≥ 30% reduction in pain from baseline) were also investigated. Results Patients taking tramadol, receiving antitumor therapy, experiencing neuropathic pain, and living far from the hospital were more likely to change analgesic strategy compared with, respectively, patients receiving low-dose morphine, palliative care, experiencing nociceptive pain, and living nearby. Factors that increased the likelihood of adherence to the analgesic regime were also associated with the likelihood of clinically meaningful pain reduction. Among adverse effects, a significantly higher percentage of patients experienced constipation in the tramadol group compared with those given morphine. Conclusions Among patients with moderate cancer pain, long-term low-dose morphine was safe and more effective than tramadol for clinically meaningful pain reduction, and patients were less likely to change the analgesic strategy.