title: Symptom Clusters in Advanced Cancer Patients: An Empirical Comparison of Statistical Methods and the Impact on Quality of Life.
abstract: BACKGROUND
  Symptom clusters in advanced cancer can influence patient outcomes. There is large heterogeneity in the methods used to identify symptom clusters.
  
  
  OBJECTIVE
  To investigate the consistency of symptom cluster composition in advanced cancer patients using different statistical methodologies for all patients across five primary cancer sites, and to examine which clusters predict functional status, a global assessment of health and global quality of life.
  
  
  METHODS
  Principal component analysis and exploratory factor analysis (with different rotation and factor selection methods) and hierarchical cluster analysis (with different linkage and similarity measures) were used on a data set of 1562 advanced cancer patients who completed the European Organization for the Research and Treatment of Cancer Quality of Life Questionnaire-Core 30.
  
  
  RESULTS
  Four clusters consistently formed for many of the methods and cancer sites: tense-worry-irritable-depressed (emotional cluster), fatigue-pain, nausea-vomiting, and concentration-memory (cognitive cluster). The emotional cluster was a stronger predictor of overall quality of life than the other clusters. Fatigue-pain was a stronger predictor of overall health than the other clusters. The cognitive cluster and fatigue-pain predicted physical functioning, role functioning, and social functioning.
  
  
  CONCLUSIONS
  The four identified symptom clusters were consistent across statistical methods and cancer types, although there were some noteworthy differences. Statistical derivation of symptom clusters is in need of greater methodological guidance. A psychosocial pathway in the management of symptom clusters may improve quality of life. Biological mechanisms underpinning symptom clusters need to be delineated by future research. A framework for evidence-based screening, assessment, treatment, and follow-up of symptom clusters in advanced cancer is essential.
authors: School of Psychology, University of Sydney, Sydney, New South Wales, Australia; University of Aberdeen, Aberdeen, UK. Electronic address: skye.dong@sydney.edu.au.
authors: Skye T
authors: ST
authors: Dong
authors: Psycho-Oncology Co-operative Research Group (PoCoG), University of Sydney, Sydney, New South Wales, Australia; University of Aberdeen, Aberdeen, UK.
authors: Daniel S J
authors: DS
authors: Costa
authors: Department of Palliative Care, Braeside Hospital, HammondCare, Sydney, New South Wales, Australia; University of Aberdeen, Aberdeen, UK.
authors: Phyllis N
authors: PN
authors: Butow
authors: Department of Palliative Care, Braeside Hospital, HammondCare, Sydney, New South Wales, Australia; HammondCare, Greenwich Hospital, Sydney, New South Wales, Australia; University of Aberdeen, Aberdeen, UK.
authors: Melanie R
authors: MR
authors: Lovell
authors: The University of Sydney Medical School, Sydney, New South Wales, Australia; University of NSW, South West Sydney Clinical School, Sydney, New South Wales, Australia; Discipline of Palliative and Supportive Services, Flinders University, Adelaide, South Australia, Australia; University of Aberdeen, Aberdeen, UK.
authors: Meera
authors: M
authors: Agar
authors: St James's Hospital, Leeds, UK; University of Aberdeen, Aberdeen, UK.
authors: Galina
authors: G
authors: Velikova
authors: Canadian Centre for Applied Research in Cancer Control, BC Cancer Research Centre, Vancouver, Canada; School of Population and Public Health, University of British Columbia, Canada; University of Aberdeen, Aberdeen, UK.
authors: Paulos
authors: P
authors: Teckle
authors: Sydney School of Public Health, University of Sydney, Sydney, New South Wales, Australia; University of Aberdeen, Aberdeen, UK.
authors: Allison
authors: A
authors: Tong
authors: Olivia Newton-John Cancer and Wellness Centre, Austin Health, Melbourne, Victoria, Australia; University of Aberdeen, Aberdeen, UK.
authors: Niall C
authors: NC
authors: Tebbutt
authors: Department of Medical Oncology, Royal North Shore Hospital, Sydney, New South Wales, Australia; University of Aberdeen, Aberdeen, UK.
authors: Stephen J
authors: SJ
authors: Clarke
authors: Canadian Centre for Applied Research in Cancer Control, BC Cancer Research Centre, Vancouver, Canada; University of Aberdeen, Aberdeen, UK.
authors: Kim
authors: K
authors: van der Hoek
authors: Psycho-Oncology Co-operative Research Group (PoCoG), University of Sydney, Sydney, New South Wales, Australia; Central Clinical School, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia; University of Aberdeen, Aberdeen, UK.
authors: Madeleine T
authors: MT
authors: King
authors: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway; University of Aberdeen, Aberdeen, UK.
authors: Peter M
authors: PM
authors: Fayers
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016000:Cluster Analysis; D003627:Data Interpretation, Statistical; D005163:Factor Analysis, Statistical; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000503:physiopathology*; D064887:Observational Studies as Topic; D025341:Principal Component Analysis; D011788:Quality of Life; D016032:Randomized Controlled Trials as Topic; D012044:Regression Analysis; D013577:Syndrome; D055815:Young Adult
keywords: EORTC QLQ-C30; Symptom clusters; advanced cancer; quality of life; statistical methods