title: Functional interference clusters in cancer patients with bone metastases: a secondary analysis of RTOG 9714.
abstract: OBJECTIVE
  To explore the relationships (clusters) among the functional interference items in the Brief Pain Inventory (BPI) in patients with bone metastases.
  
  
  METHODS
  Patients enrolled in the Radiation Therapy Oncology Group (RTOG) 9714 bone metastases study were eligible. Patients were assessed at baseline and 4, 8, and 12 weeks after randomization for the palliative radiotherapy with the BPI, which consists of seven functional items: general activity, mood, walking ability, normal work, relations with others, sleep, and enjoyment of life. Principal component analysis with varimax rotation was used to determine the clusters between the functional items at baseline and the follow-up. Cronbach's alpha was used to determine the consistency and reliability of each cluster at baseline and follow-up.
  
  
  RESULTS
  There were 448 male and 461 female patients, with a median age of 67 years. There were two functional interference clusters at baseline, which accounted for 71% of the total variance. The first cluster (physical interference) included normal work and walking ability, which accounted for 58% of the total variance. The second cluster (psychosocial interference) included relations with others and sleep, which accounted for 13% of the total variance. The Cronbach's alpha statistics were 0.83 and 0.80, respectively. The functional clusters changed at week 12 in responders but persisted through week 12 in nonresponders.
  
  
  CONCLUSIONS
  Palliative radiotherapy is effective in reducing bone pain. Functional interference component clusters exist in patients treated for bone metastases. These clusters changed over time in this study, possibly attributable to treatment. Further research is needed to examine these effects.
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Toronto, ON, Canada. Edward.Chow@sunnybrook.ca
authors.forename: Edward
authors.initials: E
authors.lastname: Chow
authors.forename: Jennifer
authors.initials: J
authors.lastname: James
authors.forename: Andrea
authors.initials: A
authors.lastname: Barsevick
authors.forename: William
authors.initials: W
authors.lastname: Hartsell
authors.forename: Sarah
authors.initials: S
authors.lastname: Ratcliffe
authors.forename: Charles
authors.initials: C
authors.lastname: Scarantino
authors.forename: Robert
authors.initials: R
authors.lastname: Ivker
authors.forename: Mack
authors.initials: M
authors.lastname: Roach
authors.forename: John
authors.initials: J
authors.lastname: Suh
authors.forename: Ivy
authors.initials: I
authors.lastname: Petersen
authors.forename: Andre
authors.initials: A
authors.lastname: Konski
authors.forename: William
authors.initials: W
authors.lastname: Demas
authors.forename: Deborah
authors.initials: D
authors.lastname: Bruner
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000339:Affect; D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000523:psychology / Q000532:radiotherapy* / Q000556:secondary*; D005260:Female; D006801:Humans; D007398:Interpersonal Relations; D017567:Karnofsky Performance Status; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement / Q000379:methods*; D025341:Principal Component Analysis; D011788:Quality of Life; D011879:Radiotherapy Dosage; D015203:Reproducibility of Results; D012890:Sleep; D016138:Walking