title: Incidental prophylactic nodal irradiation and patterns of nodal relapse in inoperable early stage NSCLC patients treated with SBRT: a case-matched analysis.
abstract: OBJECTIVE
  Reported rates of non-small cell lung cancer (NSCLC) nodal failure following stereotactic body radiation therapy (SBRT) are lower than those reported in the surgical series when matched for stage. We hypothesized that this effect was due to incidental prophylactic nodal irradiation.
  
  
  METHODS
  A prospectively collected group of medically inoperable early stage NSCLC patients from 2004 to 2010 was used to identify cases with nodal relapses. Controls were matched to cases, 2:1, controlling for tumor volume (ie, same or greater) and tumor location (ie, same lobe). Reference (normalized to equivalent dose for 2-Gy fractions [EQD2]) point doses at the ipsilateral hilum and carina, demographic data, and clinical outcomes were extracted from the medical records. Univariate conditional logistical regression analyses were performed with variables of interest.
  
  
  RESULTS
  Cases and controls were well matched except for size. The controls, as expected, had larger gross tumor volumes (P=.02). The mean ipsilateral hilar doses were 9.6 Gy and 22.4 Gy for cases and controls, respectively (P=.014). The mean carinal doses were 7.0 Gy and 9.2 Gy, respectively (P=.13). Mediastinal nodal relapses, with and without ipsilateral hilar relapse, were associated with mean ipsilateral hilar doses of 3.6 Gy and 19.8 Gy, respectively (P=.01). The conditional density plot appears to demonstrate an inverse dose-effect relationship between ipsilateral hilar normalized total dose and risk of ipsilateral hilar relapse.
  
  
  CONCLUSIONS
  Incidental hilar dose greater than 20 Gy is significantly associated with fewer ipsilateral hilar relapses in inoperable early stage NSCLC patients treated with SBRT.
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Auckland City Hospital, Auckland, New Zealand.
authors.forename: Louis
authors.initials: L
authors.lastname: Lao
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Hope
authors.affiliation: Department of Biostatistics, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Manjula
authors.initials: M
authors.lastname: Maganti
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Anthony
authors.initials: A
authors.lastname: Brade
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Andrea
authors.initials: A
authors.lastname: Bezjak
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Elantholi P
authors.initials: EP
authors.lastname: Saibishkumar
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Meredith
authors.initials: M
authors.lastname: Giuliani
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Alexander
authors.initials: A
authors.lastname: Sun
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada. Electronic address: john.cho@rmp.uhn.on.ca.
authors.forename: B C John
authors.initials: BC
authors.lastname: Cho
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000517:prevention & control / Q000601:surgery; D000328:Adult; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000517:prevention & control / Q000601:surgery*; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000517:prevention & control / Q000601:surgery; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000517:prevention & control / Q000601:surgery*; D015182:Lymphatic Irradiation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D011446:Prospective Studies; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D012044:Regression Analysis; D055502:Secondary Prevention; D047368:Tumor Burden