title: Quality of life in breast cancer patients--a quantile regression analysis.
abstract: BACKGROUND
  Quality of life study has an important role in health care especially in chronic diseases, in clinical judgment and in medical resources supplying. Statistical tools like linear regression are widely used to assess the predictors of quality of life. But when the response is not normal the results are misleading. The aim of this study is to determine the predictors of quality of life in breast cancer patients, using quantile regression model and compare to linear regression.
  
  
  METHODS
  A cross-sectional study conducted on 119 breast cancer patients that admitted and treated in chemotherapy ward of Namazi hospital in Shiraz. We used QLQ-C30 questionnaire to assessment quality of life in these patients. A quantile regression was employed to assess the assocciated factors and the results were compared to linear regression. All analysis carried out using SAS.
  
  
  RESULTS
  The mean score for the global health status for breast cancer patients was 64.92+/-11.42. Linear regression showed that only grade of tumor, occupational status, menopausal status, financial difficulties and dyspnea were statistically significant. In spite of linear regression, financial difficulties were not significant in quantile regression analysis and dyspnea was only significant for first quartile. Also emotion functioning and duration of disease statistically predicted the QOL score in the third quartile.
  
  
  CONCLUSIONS
  The results have demonstrated that using quantile regression leads to better interpretation and richer inference about predictors of the breast cancer patient quality of life.
authors.affiliation: Research Center of Gastroenterology and Liver Diseases, Shahid Beheshti University MC, Tehran, Iran. Aminphg@gmail.com
authors.forename: Mohamad Amin
authors.initials: MA
authors.lastname: Pourhoseingholi
authors.forename: Azadeh
authors.initials: A
authors.lastname: Safaee
authors.forename: Bijan
authors.initials: B
authors.lastname: Moghimi-Dehkordi
authors.forename: Bahram
authors.initials: B
authors.lastname: Zeighami
authors.forename: Soghrat
authors.initials: S
authors.lastname: Faghihzadeh
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Tabatabaee
authors.forename: Asma
authors.initials: A
authors.lastname: Pourhoseingholi
mesh_terms: D000222:Adaptation, Physiological; D000223:Adaptation, Psychological; D000328:Adult; D000367:Age Factors; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000523:psychology* / Q000601:surgery; D017024:Chemotherapy, Adjuvant; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007492:Iran; D016014:Linear Models; D011788:Quality of Life; D018570:Risk Assessment; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires