title: Predictors of adherence to different types and doses of supervised exercise during breast cancer chemotherapy.
abstract: BACKGROUND
  Exercise is beneficial for breast cancer patients during chemotherapy but adherence to different types and doses of exercise is a challenge. The purpose of this study was to examine predictors of adherence to different types and doses of exercise during breast cancer chemotherapy in a multicenter randomized controlled trial.
  
  
  METHODS
  Breast cancer patients in Edmonton, Vancouver, and Ottawa, Canada receiving chemotherapy (N = 301) were randomized to a standard dose of 25-30 minutes of aerobic exercise (STAN), a higher dose of 50-60 minutes of aerobic exercise (HIGH), or a higher dose of 50-60 minutes of combined aerobic and resistance exercise (COMB). Predictors included demographic, medical, fitness, and quality of life variables. Exercise adherence was measured as the percentage of supervised exercise sessions completed.
  
  
  RESULTS
  Overall adherence to the supervised exercise sessions was 73% (SD = 24%). In a multivariate regression model, six independent predictors explained 26.4% (p < 0.001) of the variance in exercise adherence. Higher exercise adherence was achieved by breast cancer patients in Vancouver (p < 0.001), with fewer endocrine symptoms (p = 0.009), randomized to STAN (p = 0.009), with fewer exercise limitations (p = 0.009), receiving shorter chemotherapy protocols (p = 0.015), and with higher VO2peak (p = 0.017). Disease stage (p for interaction = 0.015) and body mass index (p for interaction = 0.030) interacted with group assignment to predict adherence. For disease stage, patients with stage I/IIa disease adhered equally well to all three exercise interventions whereas patients with stage IIb/III disease adhered better to the STAN intervention than the two higher dose exercise interventions. For body mass index, healthy weight patients adhered equally well to all three exercise interventions whereas overweight patients adhered best to STAN and worst to COMB; and obese patients adhered best to STAN and worst to HIGH.
  
  
  CONCLUSIONS
  Determinants of exercise adherence in breast cancer patients receiving chemotherapy are multidisciplinary and may vary by the exercise prescription.
authors.forename: Kerry S
authors.initials: KS
authors.lastname: Courneya
authors.forename: Roanne J
authors.initials: RJ
authors.lastname: Segal
authors.forename: Karen
authors.initials: K
authors.lastname: Gelmon
authors.forename: John R
authors.initials: JR
authors.lastname: Mackey
authors.forename: Christine M
authors.initials: CM
authors.lastname: Friedenreich
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yasui
authors.forename: Robert D
authors.initials: RD
authors.lastname: Reid
authors.forename: Carolyn
authors.initials: C
authors.lastname: Proulx
authors.forename: Linda
authors.initials: L
authors.lastname: Trinh
authors.forename: Lianne B
authors.initials: LB
authors.lastname: Dolan
authors.forename: Evyanne
authors.initials: E
authors.lastname: Wooding
authors.forename: James R
authors.initials: JR
authors.lastname: Vallerand
authors.forename: Donald C
authors.initials: DC
authors.lastname: McKenzie
mesh_terms: D000328:Adult; D000971:Antineoplastic Combined Chemotherapy Protocols; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000628:therapy*; D002170:Canada; D015444:Exercise; D005081:Exercise Therapy / Q000379:methods; D005260:Female; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D010349:Patient Compliance; D011446:Prospective Studies; D011788:Quality of Life; D012044:Regression Analysis