title: The state of science in the study of cancer symptom clusters.
abstract: OBJECTIVE
  To provide an integrative review of the literature on the science of symptom clusters in patients with cancer and establish implications for future studies.
  
  
  METHODS
  Sixty-one articles about cancer symptom clusters were selected for review from results of a search in MEDLINE, CINAHL, PsycINFO, Sociological Abstracts and Cochrane databases from 1950 to 2010.
  
  
  RESULTS
  This review discusses the current research on the definitions, theoretical frameworks, measurements, outcomes, and interventions of symptom clusters in oncology. Although symptom clusters were identified as groups of several related and coexisted symptoms, researchers had different opinion on the least number of and relationships among symptoms in a cluster. Four theoretical frameworks were used, but none of them were specific to guide research in symptom clusters for general cancer population. Most-common symptom approach and all-possible symptom approach had their own characteristics and methods for cluster identification. Functional status and quality of life were major outcomes that were negatively associated with the number or severity of symptom clusters. Interventions with multiple or central symptoms in clusters were two potential ways to improve patients' symptom experience.
  
  
  CONCLUSIONS
  Despite advances in understanding of symptom clusters, further research is needed to define clusters operationally, and to develop appropriate theoretical frameworks. Methods of cluster identification need further comparison to see which offers the best understanding of symptom clusters. More studies with cross-sectional or longitudinal designs are necessary to explore influences of symptom clusters on patient outcomes, and interventions on symptom clusters.
authors.affiliation: School of Nursing, University of Pennsylvania, Claire M. Fagin Hall, 418 Curie Boulevard, Philadelphia, PA 19104-4217, USA. canhuax@nursing.upenn.edu
authors.forename: Canhua
authors.initials: C
authors.lastname: Xiao
mesh_terms: D000203:Activities of Daily Living; D000293:Adolescent; D000328:Adult; D002648:Child; D016000:Cluster Analysis; D003430:Cross-Sectional Studies; D003863:Depression / Q000209:etiology; D005221:Fatigue / Q000209:etiology; D006801:Humans; D008137:Longitudinal Studies; D009369:Neoplasms / Q000150:complications* / Q000401:mortality / Q000523:psychology / Q000628:therapy*; D009730:Nursing Assessment; D015399:Nursing Research / Q000458:organization & administration*; D009742:Nursing Theory; D009859:Oncology Nursing / Q000458:organization & administration*; D011788:Quality of Life; D012107:Research Design; D007319:Sleep Initiation and Maintenance Disorders / Q000209:etiology