Matrix stimulation in cancer pain: Methodology, safety and effectiveness.

BACKGROUND: This feasibility study addresses the applicability of matrix electrodes for the reduction of ongoing pain in cancer patients via low-frequency electrical stimulation (LFS).

METHODS: Low-frequency matrix stimulation (4 Hz) was applied to the skin within the 'Head's zones' referring to the tumour localization of cancer pain patients. Pain at baseline was compared to a 3-day treatment interval consisting of 5 min of matrix stimulation in the morning and evening followed by a 3-day follow-up period without therapy. Main outcome parameters included numeric rating scale values (rating scale 0-100), painDETECT, HADS, and German pain questionnaire, as well as the opioid intake, calculated as the oral morphine equivalent (OME).

RESULTS: Twenty patients with cancer pain (aged 64.4 ± 10.3; 9 women) were examined. In the majority of patients, the pain was classified as nociceptive. The mean pain reduction achieved by matrix therapy was 30%, under stable daily controlled-release opioid doses between 177 and 184 mg/day (OME). Seventeen patients (85%) were responders, defined by a pain reduction of at least 30%, while four responders experienced a pain reduction of over 50%. The only side effect was short-term erythema.

CONCLUSION: Findings are consistent with the concept of synaptic long-term depression in cancer pain induced after conditioning LFS. Despite the short, but well-tolerated, treatment duration of 2 × 5 min/day, effects persisted throughout the 3-day follow-up.

SIGNIFICANCE: Cutaneous neuromodulation using LFS via a matrix electrode has been shown to be a safe intervention for effectively reducing cancer pain in palliative care patients.