title: Propensity score-based comparison of long-term outcomes with 3-dimensional conformal radiotherapy vs intensity-modulated radiotherapy for esophageal cancer.
abstract: OBJECTIVE
  Although 3-dimensional conformal radiotherapy (3D-CRT) is the worldwide standard for the treatment of esophageal cancer, intensity modulated radiotherapy (IMRT) improves dose conformality and reduces the radiation exposure to normal tissues. We hypothesized that the dosimetric advantages of IMRT should translate to substantive benefits in clinical outcomes compared with 3D-CRT.
  
  
  METHODS
  An analysis was performed of 676 nonrandomized patients (3D-CRT, n=413; IMRT, n=263) with stage Ib-IVa (American Joint Committee on Cancer 2002) esophageal cancers treated with chemoradiotherapy at a single institution from 1998-2008. An inverse probability of treatment weighting and inclusion of propensity score (treatment probability) as a covariate were used to compare overall survival time, interval to local failure, and interval to distant metastasis, while accounting for the effects of other clinically relevant covariates. The propensity scores were estimated using logistic regression analysis.
  
  
  RESULTS
  A fitted multivariate inverse probability weighted-adjusted Cox model showed that the overall survival time was significantly associated with several well-known prognostic factors, along with the treatment modality (IMRT vs 3D-CRT, hazard ratio 0.72, P<.001). Compared with IMRT, 3D-CRT patients had a significantly greater risk of dying (72.6% vs 52.9%, inverse probability of treatment weighting, log-rank test, P<.0001) and of locoregional recurrence (P=.0038). No difference was seen in cancer-specific mortality (Gray's test, P=.86) or distant metastasis (P=.99) between the 2 groups. An increased cumulative incidence of cardiac death was seen in the 3D-CRT group (P=.049), but most deaths were undocumented (5-year estimate, 11.7% in 3D-CRT vs 5.4% in IMRT group, Gray's test, P=.0029).
  
  
  CONCLUSIONS
  Overall survival, locoregional control, and noncancer-related death were significantly better after IMRT than after 3D-CRT. Although these results need confirmation, IMRT should be considered for the treatment of esophageal cancer.
authors.affiliation: Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas, USA. SHLin@mdanderson.org
authors.forename: Steven H
authors.initials: SH
authors.lastname: Lin
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.forename: Bevan
authors.initials: B
authors.lastname: Myles
authors.forename: Peter F
authors.initials: PF
authors.lastname: Thall
authors.forename: Wayne L
authors.initials: WL
authors.lastname: Hofstetter
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Swisher
authors.forename: Jaffer A
authors.initials: JA
authors.lastname: Ajani
authors.forename: James D
authors.initials: JD
authors.lastname: Cox
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Komaki
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Liao
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D002277:Carcinoma / Q000188:drug therapy / Q000401:mortality / Q000532:radiotherapy / Q000556:secondary; D002423:Cause of Death; D059186:Chemoradiotherapy, Adjuvant / Q000009:adverse effects / Q000379:methods / Q000401:mortality; D004938:Esophageal Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000532:radiotherapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D057216:Propensity Score; D016016:Proportional Hazards Models; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods / Q000401:mortality; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods / Q000401:mortality; D059039:Standard of Care