title: The Impact of Intensity Modulated Radiation Therapy on Hospitalization Outcomes in the SEER-Medicare Population With Anal Squamous Cell Carcinoma.
abstract: We examined the impact of intensity modulated radiation therapy (IMRT) on hospitalization rates in the Surveillance, Epidemiology, and End Results (SEER)-Medicare population with anal squamous cell carcinoma (SCC).
  
  
  
  We performed a retrospective cohort study using the SEER-Medicare database. We identified patients with nonmetastatic anal SCC diagnosed between 2001 and 2011 and treated with chemoradiation therapy. We assessed the relation between IMRT and first hospitalization by use of a multivariate competing-risk model, as well as instrumental variable analysis, using provider IMRT affinity as our instrument.
  
  
  
  Of the 1165 patients included in our study, 458 (39%) received IMRT. IMRT use increased over time and was associated more with regional and provider characteristics than with patient characteristics. The 3- and 6-month cumulative incidences of first hospitalization were 41.9% (95% confidence interval [CI], 37.3%-46.4%) and 47.6% (95% CI, 43.0%-52.2%), respectively, for the IMRT cohort and 46.7% (95% CI, 43.0%-50.4%) and 52.1% (95% CI, 48.4%-55.7%), respectively, for the non-IMRT cohort. IMRT was associated with a decreased hazard of first hospitalization compared with 3-dimensional radiation techniques (hazard ratio, 0.70; 95% CI, 0.58-0.84; P=.0002). Instrumental variable analysis suggested an even greater reduction in hospitalizations with IMRT after controlling for unmeasured confounders. There was a trend toward improved overall survival with IMRT, with an adjusted hazard ratio of 0.77 (95% CI, 0.59-1.00; P=.05).
  
  
  
  The use of IMRT is associated with reduced hospitalizations in elderly patients with anal SCC. Further work is warranted to understand the long-term health and cost impact of IMRT, particularly for patient subgroups most at risk of toxicity and hospitalization.
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California. Electronic address: erqiliu@stanford.edu.
authors.forename: Erqi L
authors.initials: EL
authors.lastname: Pollom
authors.affiliation: Department of Health Research and Policy, Stanford University School of Medicine, Stanford, California.
authors.forename: Guanying
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California.
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Harris
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California.
authors.forename: Albert C
authors.initials: AC
authors.lastname: Koong
authors.affiliation: Center for Health Policy-Center for Primary Care and Outcomes Research, Stanford University School of Medicine, Stanford, California.
authors.forename: Eran
authors.initials: E
authors.lastname: Bendavid
authors.affiliation: Center for Health Policy-Center for Primary Care and Outcomes Research, Stanford University School of Medicine, Stanford, California.
authors.forename: Jay
authors.initials: J
authors.lastname: Bhattacharya
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Chang
mesh_terms: D000368:Aged; D001005:Anus Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D002294:Carcinoma, Squamous Cell / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D016001:Confidence Intervals; D015986:Confounding Factors, Epidemiologic; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data*; D008875:Middle Aged; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D050397:Radiotherapy, Intensity-Modulated / Q000401:mortality / Q000706:statistics & numerical data* / Q000639:trends; D012189:Retrospective Studies; D018426:SEER Program / Q000706:statistics & numerical data*; D015996:Survival Rate; D016896:Treatment Outcome; D014481:United States