Effect of Patient-Controlled Transcutaneous Electrical Acupoint Stimulation on Quality of Life in Chronic Cancer Pain

Inclusion Criteria: * Age between 18 and 80 years, regardless of gender; * Diagnosis of primary or metastatic malignant tumor confirmed by histopathology and/or cytology, consistent with the American Cancer Society criteria for malignancy; * Presence of cancer-related pain, defined as an average Numeric Rating Scale (NRS) score ≥ 2 over the preceding week or current regular use of opioid analgesics; * Life expectancy ≥ 3 months; * Eastern Cooperative Oncology Group Performance Status (ECOG-PS) score ≤ 2, stable vital signs, clear consciousness, intact pain perception, unimpaired communication, ability to cooperate with study procedures and complete assessments; * Provision of signed informed consent by the patient or their legal guardian after comprehensive explanation of the study; Exclusion Criteria: * Pain not attributable to cancer; * Severe cardiopulmonary dysfunction or respiratory depression; * Implantation of cardiac pacemaker or metallic implants at stimulation sites; * Local skin lesions or conditions unsuitable for TEAS at the acupoint sites; * Severe psychiatric disorders or significant cognitive impairment; * Concurrent participation in other clinical trials that may interfere with the outcome evaluation of this study; * Previous history of transcutaneous electrical acupoint stimulation (TEAS) or transcutaneous electrical nerve stimulation (TENS);