title: Factors influencing participation in a randomized controlled resistance exercise intervention study in breast cancer patients during radiotherapy.
abstract: BACKGROUND
  Over the past years knowledge about benefits of physical activity after cancer is evolving from randomized exercise intervention trials. However, it has been argued that results may be biased by selective participation. Therefore, we investigated factors influencing participation in a randomized exercise intervention trial for breast cancer patients.
  
  
  METHODS
  Non-metastatic breast cancer patients were systematically screened for a randomized exercise intervention trial on cancer-related fatigue. Participants and nonparticipants were compared concerning sociodemographic characteristics (age, marital status, living status, travel time to the training facility), clinical data (body-mass-index, tumor stage, tumor size and lymph node status, comorbidities, chemotherapy), fatigue, and physical activity. Reasons for participation or declination were recorded.
  
  
  RESULTS
  117 patients (52 participants, 65 nonparticipants) were evaluable for analysis. Multiple regression analyses revealed significantly higher odds to decline participation among patients with longer travel time (p=0.0012), living alone (p=0.039), with more comorbidities (0.031), previous chemotherapy (p=0.0066), of age≥70 years (p=0.025), or being free of fatigue (p=0.0007). No associations were found with BMI or physical activity. By far the most frequently reported reason for declination of participation was too long commuting time to the training facility.
  
  
  CONCLUSIONS
  Willingness of breast cancer patients to participate in a randomized exercise intervention study differed by sociodemographic factors and health status. Neither current physical activity level nor BMI appeared to be selective for participation. Reduction of personal inconveniences and time effort, e.g. by decentralized training facilities or flexible training schedules, seem most promising for enhancing participation in exercise intervention trials.
  
  
  BACKGROUND
  Registered at ClinicalTrials.gov: NCT01468766 (October 2011).
authors.affiliation: Unit of Physical Activity and Cancer, Department of Preventive Oncology, German Cancer Research Center and National Center for Tumor Diseases, Im Neuenheimer Feld 460, 69120, Heidelberg, Germany. sandragollhofer@yahoo.de.
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Gollhofer
authors.affiliation: Unit of Physical Activity and Cancer, Department of Preventive Oncology, German Cancer Research Center and National Center for Tumor Diseases, Im Neuenheimer Feld 460, 69120, Heidelberg, Germany. joachim.wiskemann@nct-heidelberg.de.|Department of Medical Oncology, National Center for Tumor Diseases, Im Neuenheimer Feld 460, 69120, Heidelberg, Germany. joachim.wiskemann@nct-heidelberg.de.|National Center for Tumor Diseases (NCT), Divisions of Medical Oncology and Preventive Oncology, Im Neuenheimer Feld 460, 69120, Heidelberg, Germany. joachim.wiskemann@nct-heidelberg.de.
authors.forename: Joachim
authors.initials: J
authors.lastname: Wiskemann
authors.affiliation: Unit of Physical Activity and Cancer, Department of Preventive Oncology, German Cancer Research Center and National Center for Tumor Diseases, Im Neuenheimer Feld 460, 69120, Heidelberg, Germany. m.schmidt@dkfz-heidelberg.de.|Unit of Environmental Epidemiology, German Cancer Research Center, Im Neuenheimer Feld 280, 69120, Heidelberg, Germany. m.schmidt@dkfz-heidelberg.de.
authors.forename: Martina E
authors.initials: ME
authors.lastname: Schmidt
authors.affiliation: Unit of Physical Activity and Cancer, Department of Preventive Oncology, German Cancer Research Center and National Center for Tumor Diseases, Im Neuenheimer Feld 460, 69120, Heidelberg, Germany. oliver.klassen@nct-heidelberg.de.
authors.forename: Oliver
authors.initials: O
authors.lastname: Klassen
authors.affiliation: Department of Preventive Oncology, National Center for Tumor Diseases, Im Neuenheimer Feld 460, 69120, Heidelberg, Germany. neli.ulrich@hci.utah.edu.
authors.forename: Cornelia M
authors.initials: CM
authors.lastname: Ulrich
authors.affiliation: Department of Radiation Oncology, University of Heidelberg Medical Center, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. jan.oelmann@med.uni-heidelberg.de.
authors.forename: Jan
authors.initials: J
authors.lastname: Oelmann
authors.affiliation: Department of Radiation Oncology, University of Heidelberg Medical Center, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. hof@strahlentherapie-neustadt.de.
authors.forename: Holger
authors.initials: H
authors.lastname: Hof
authors.affiliation: Department of Medical Oncology, National Center for Tumor Diseases, Im Neuenheimer Feld 460, 69120, Heidelberg, Germany. karin.potthoff@med.uni-heidelberg.de.|Department of Radiation Oncology, University of Heidelberg Medical Center, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. karin.potthoff@med.uni-heidelberg.de.
authors.forename: Karin
authors.initials: K
authors.lastname: Potthoff
authors.affiliation: Unit of Physical Activity and Cancer, Department of Preventive Oncology, German Cancer Research Center and National Center for Tumor Diseases, Im Neuenheimer Feld 460, 69120, Heidelberg, Germany. k.steindorf@dkfz-heidelberg.de.|Unit of Environmental Epidemiology, German Cancer Research Center, Im Neuenheimer Feld 280, 69120, Heidelberg, Germany. k.steindorf@dkfz-heidelberg.de.
authors.forename: Karen
authors.initials: K
authors.lastname: Steindorf
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000150:complications* / Q000532:radiotherapy; D015897:Comorbidity; D005081:Exercise Therapy; D005221:Fatigue / Q000209:etiology / Q000628:therapy*; D005260:Female; D006304:Health Status; D006801:Humans; D008875:Middle Aged; D010342:Patient Acceptance of Health Care; D012111:Residence Characteristics; D013997:Time Factors; D014186:Transportation
chemical_list: D000970:Antineoplastic Agents