title: Does delay in starting treatment affect the outcomes of radiotherapy? A systematic review.
abstract: OBJECTIVE
  The objective of this study was to synthesize what is known about the relationship between delay in radiotherapy (RT) and the outcomes of RT.
  
  
  METHODS
  A systematic review of the world literature was conducted to identify studies that described the association between delay in RT and the probability of local control, metastasis, and/or survival. Studies were classified by clinical and methodologic criteria and their results were combined using a random-effects model.
  
  
  RESULTS
  A total of 46 relevant studies involving 15,782 patients met our minimum methodologic criteria of validity; most (42) were retrospective observational studies. Thirty-nine studies described rates of local recurrence, 21 studies described rates of distant metastasis, and 19 studies described survival. The relationship between delay and the outcomes of RT had been studied in diverse situations, but most frequently in breast cancer (21 studies) and head and neck cancer (12 studies). Combined analysis showed that the 5-year local recurrence rate (LRR) was significantly higher in patients treated with adjuvant RT for breast cancer more than 8 weeks after surgery than in those treated within 8 weeks of surgery (odds ratio [OR] = 1.62, 95% confidence interval [CI], 1.21 to 2.16). Combined analysis also showed that the LRR was significantly higher among patients who received postoperative RT for head and neck cancer more than 6 weeks after surgery than among those treated within 6 weeks of surgery (OR = 2.89; 95% CI, 1.60 to 5.21). There was little evidence about the impact of delay in RT on the risk of metastases or the probability of long-term survival in any situation.
  
  
  CONCLUSIONS
  Delay in the initiation of RT is associated with an increase [corrected] in LRR in breast cancer and head and neck cancer. Delays in starting RT should be as short as reasonably achievable.
authors.affiliation: Division of Cancer Care and Epidemiology, Queen's Cancer Research Institute, and Kingston Regional Cancer Centre, Kingston, Canada.
authors.forename: Jenny
authors.initials: J
authors.lastname: Huang
authors.forename: Lisa
authors.initials: L
authors.lastname: Barbera
authors.forename: Melissa
authors.initials: M
authors.lastname: Brouwers
authors.forename: George
authors.initials: G
authors.lastname: Browman
authors.forename: William J
authors.initials: WJ
authors.lastname: Mackillop
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D005260:Female; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D009362:Neoplasm Metastasis; D009364:Neoplasm Recurrence, Local; D011878:Radiotherapy / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors; D013534:Survival; D013997:Time Factors; D016896:Treatment Outcome