title: The impact of overall treatment time on the results of radiotherapy for nonsmall cell lung carcinoma.
abstract: OBJECTIVE
  We evaluated the impact of overall treatment time on the disease-free survival (DFS) and local control after radiotherapy for nonsmall cell lung carcinoma.
  
  
  METHODS
  One hundred fifty-three cases considered as responders to radiotherapy were retrospectively analyzed. Patients with Karnofsky status < 70, pretreated with chemotherapy and with pleural or pericardial effusion, were excluded from the analysis. Radiation dose homogenization was done with calculation of the normalized total dose without (NTD) and with time correction (NTD-T) for alpha/beta = 10 Gy.
  
  
  RESULTS
  Kaplan-Meier curves for 2-year DFS showed that any analysis based on radiation dose can prove to be erroneous when the time factor is neglected. Although there was no difference between the 47-55 Gy and 56-64 Gy NTD groups, a log rank test revealed a strong difference (p < 0.0002) between NTD-T groups. No difference was observed for patients with mediastinal involvement. Logistic regression analysis showed a statistical association of dose on 2-year local progression-free probability for different time compartments. For those cases without mediastinal involvement, the daily dose lost because of treatment protraction beyond 20 days after the beginning of radiotherapy was estimated to 0.2 Gy/day. When all cases were considered together this was calculated to 0.45 Gy/day.
  
  
  CONCLUSIONS
  Time factor should not be underestimated when evaluating the results of radiotherapy for nonsmall cell lung cancer. There is strong evidence that prolonged overall treatment time could be a major cause of the failure of radiotherapy to control the local disease.
authors.affiliation: Department of Radiotherapy-Oncology, University Hospital of Iraklion, Crete, Greece.
authors.forename: M
authors.initials: M
authors.lastname: Koukourakis
authors.forename: G
authors.initials: G
authors.lastname: Hlouverakis
authors.forename: L
authors.initials: L
authors.lastname: Kosma
authors.forename: J
authors.initials: J
authors.lastname: Skarlatos
authors.forename: J
authors.initials: J
authors.lastname: Damilakis
authors.forename: A
authors.initials: A
authors.lastname: Giatromanolaki
authors.forename: D
authors.initials: D
authors.lastname: Yannakakis
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D018572:Disease-Free Survival; D006801:Humans; D008175:Lung Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012044:Regression Analysis; D013997:Time Factors