title: Effects of circadian rhythms and treatment times on the response of radiotherapy for painful bone metastases.
abstract: BACKGROUND
  Previous studies have observed how the time of radiotherapy delivery can impact toxicities and outcomes. The goal of this study was to determine whether treatment time influenced radiotherapy response for bone metastases.
  
  
  METHODS
  Patients who received radiation treatment to painful bone metastases from January 2000 to December 2010 were included in our analysis. Demographic and treatment information including performance status, primary site, treatment dose and fraction, and response were collected prospectively. Treatment times were extracted from patient medical records. Patients were allocated to 8:00 AM-11:00 AM, 11:01 AM-2:00 PM, or 2:01 PM-5:00 PM cohorts based on their treatment times. To compare treatment response between the three cohorts, the Fisher exact test was used. A two-sided P value of <0.05 was considered statistically significant. Analysis was repeated with males and females separately.
  
  
  RESULTS
  A total of 194 patients were included. The median age was 68 years and 55.5% of patients responded to treatment. The dose and fraction of radiation received differed significantly between treatment cohorts using all allocation methods. Females in the 11:01 AM-2:00 PM cohort exhibited a significantly higher response rate (P=0.02) and differing proportions of response types (P=0.03) compared to the 8:00 AM- 11:00 AM and 2:01 PM-5:00 PM cohorts when allocated using all treatment times. No significant differences in response were seen between cohorts when all patients were analysed together or analysed for males only.
  
  
  CONCLUSIONS
  Treatment time may affect response in female patients receiving radiotherapy for painful bone metastases. Subsequent chronotherapy studies in radiation should investigate these gender differences.
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Chan
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Liying
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Leigha
authors.initials: L
authors.lastname: Rowbottom
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Rachel
authors.initials: R
authors.lastname: McDonald
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Georg A
authors.initials: GA
authors.lastname: Bjarnason
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: May
authors.initials: M
authors.lastname: Tsao
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Barnes
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Cyril
authors.initials: C
authors.lastname: Danjoux
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Marko
authors.initials: M
authors.lastname: Popovic
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Henry
authors.initials: H
authors.lastname: Lam
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Carlo
authors.initials: C
authors.lastname: DeAngelis
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada. edward.chow@sunnybrook.ca.
authors.forename: Edward
authors.initials: E
authors.lastname: Chow
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000150:complications / Q000532:radiotherapy* / Q000556:secondary; D001943:Breast Neoplasms / Q000473:pathology*; D000072716:Cancer Pain / Q000209:etiology / Q000532:radiotherapy*; D019454:Chronotherapy; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000473:pathology*; D012737:Sex Factors; D013997:Time Factors; D016896:Treatment Outcome
keywords: Chronotherapy; bone metastases; circadian rhythms; radiotherapy; treatment response