Efficacy and Safety of Transcutaneous Auricular Vagus Nerve Stimulation on Radiotherapy-Related Neuropathic Pain

Inclusion Criteria:

1. Male or female patients aged ≥18 years with an estimated survival of at least 5 months;
2. Prior radiotherapy for histologically confirmed cancer ≥ 6 months prior to study entry;
3. Pain for at least 4 weeks with an average intensity of ≥ 4 on an 11-point numeric rating scale (NRS) in the run-in period, and pain locations in accordance with radiated innervated areas, e.g. head, face, neck and arms;
4. Neuropathic pain defined according to clinical history, symptoms, physical signs, and a score ≥ 12 in the Chinese version of Leeds Assessment of Neuropathic Symptoms and Signs questionnaire (LANSS) by two trained and experienced neurology specialists.

Exclusion Criteria:

1. Current diagnosis of tumor recurrence or metastasis and evidence of tumor-associated pain;
2. Patients with non-radiotherapy induced neuropathic pain, e.g. postherpetic neuralgia, diabetes mellitus, HIV infection, spinal cord injury and other neurological disease;
3. Use of carbamazepine, gabapentin, pregabalin, TaVNS or transcranial magnetic stimulation within the last 30 days prior to study entry;
4. Other ongoing treatment for neuropathic pain, including antidepressants with norepinephrine and serotonin reuptake inhibition, calcium channel α2-δ ligands and other anticonvulsant medications, and topical lidocaine;
5. Concomitant medication that may cause an adverse interaction with pregabalin, including sedative (e.g., benzodiazepines);
6. Significant renal impairment: plasma creatinine\>1.5mg/ml, creatinine clearance \< 60 mL/min;
7. History of anaphylactic response to pregabalin;
8. Ulceration of the auricle skin; Diagnosis of mental illness, peptic ulcer,AV III degree block, heart rate\< 50/min, heart rate corrected QT interval \> 450ms;
9. Patients with cardiac pacemakers or implanted ECG monitoring equipment;
10. Evidence of severe systemic diseases;
11. Subjects with any other condition which, in the investigator's judgment might interfere the outcome of the study;
12. Refuse to provide written informed consent;
13. Cognitive function and language skills are insufficient to complete study questionnaires;
14. Pregnant or lactating women.