Development of a symptom cluster scale for breast cancer patients undergoing adjuvant chemotherapy based on the Chinese population: a Delphi-based study

Breast cancer is the most common malignancy among women in China.Postoperative adjuvant chemotherapy can reduce the risk of recurrence, but it can also give rise to complex symptom clusters that significantly affect patients’ quality of life and treatment adherence. Currently, specific assessment tools targeting symptom clusters remain scarce, and existing instruments lack characteristics relevant to the Chinese healthcare context. To develop and preliminarily validate a symptom cluster scale for patients receiving adjuvant chemotherapy after breast cancer surgery, integrating Traditional Chinese Medicine symptoms and TCM diagnostic information. An initial item pool was constructed through systematic literature review, retrospective clinical data mining, TCM theoretical analysis, semi-structured patient interviews, and expert roundtable discussions. A two-round Delphi survey was conducted among 26 multidisciplinary experts to evaluate and reduce symptom items according to criteria of relevance and importance. Subsequently, the preliminary scale was administered to breast cancer patients undergoing postoperative adjuvant chemotherapy. The psychometric properties of the scale were assessed through item analysis, reliability testing (Cronbach’s α, 95% CI: 0.892–0.931), and exploratory factor analysis (EFA). The effective response rate for both rounds of the Delphi expert consultation was 100%, and the expert authority coefficient was 0.941. The final scale comprised 40 items, from which 11 distinct factors were extracted through exploratory factor analysis. These factors were identified as the following symptom clusters: (1) cognitive-sleep disturbance symptom cluster, (2) digestive-nutritional dysregulation symptom cluster, (3) emotional abnormality symptom cluster, (4) chest and hypochondriac discomfort-pain symptom cluster, (5) menopausal symptom cluster, (6) head discomfort symptom cluster, (7) upper gastrointestinal discomfort symptom cluster, (8) multi-system dysfunction symptom cluster, (9) taste abnormality symptom cluster, (10) defecation abnormality symptom cluster, and (11) a separate cluster comprising skin pruritus and constipation. The 11-factor solution accounted for 61.975% of the total variance.The scale demonstrated good internal consistency (Cronbach’s α = 0.912, 95% CI: 0.892–0.931), satisfactory content validity (I- CVI range: 0.83–1.00, S- CVI/Ave = 0.92), and good convergent and discriminant validity. The Symptom Cluster Scale for Breast Cancer Patients Undergoing Postoperative Adjuvant Chemotherapy is a valid and reliable instrument. The newly developed scale demonstrates good reliability and validity in this preliminary validation phase. It aligns with the cultural habits of Chinese patients, integrates symptom dimensions from both traditional and modern medicine, and provides a culturally adapted, comprehensive symptom assessment tool for clinical practice. However, as this is a preliminary validation, confirmatory factor analysis in independent samples and external validation are required before clinical implementation.