title: Stereotactic body radiation therapy and 3-dimensional conformal radiotherapy for stage I non-small cell lung cancer: A pooled analysis of biological equivalent dose and local control.
abstract: OBJECTIVE
  To determine the relationship between tumor control probability (TCP) and biological effective dose (BED) for radiation therapy in medically inoperable stage I non-small cell lung cancer (NSCLC).
  
  
  METHODS
  Forty-two studies on 3-dimensional conformal radiation therapy (3D-CRT) and SBRT for stage I NSCLC were reviewed for tumor control (TC), defined as crude local control ≥ 2 years, as a function of BED. For each dose-fractionation schedule, BED was calculated at isocenter using the linear quadratic (LQ) and universal survival curve (USC) models. A scatter plot of TC versus BED was generated and fitted to the standard TCP equation for both models.
  
  
  RESULTS
  A total of 2696 patients were included in this study (SBRT: 1640; 3D-CRT: 1056). Daily fraction size was 1.2-4 Gy (total dose: 48-102.9) with 3D-CRT and 6-26 (total dose: 20-66) with SBRT. Median BED was 118.6 Gy (range, 68.5-320.3) and 95.6 Gy (range, 46.1-178.1) for the LQ and USC models, respectively. According to the LQ model, BED to achieve 50% TC (TCD50) was 61 Gy (95% confidence interval, 50.2-71.1). TCP as a function of BED was sigmoidal, with TCP ≥ 90% achieved with BED ≥ 159 Gy and 124 Gy for the LQ and USC models, respectively.
  
  
  CONCLUSIONS
  Dose-escalation beyond a BED 159 by LQ model likely translates into clinically insignificant gain in TCP but may result in clinically significant toxicity. When delivered with SBRT, BED of 159 Gy corresponds to a total dose of 53 Gy in 3 fractions at the isocenter.
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
authors.forename: Niraj
authors.initials: N
authors.lastname: Mehta
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: King
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
authors.forename: Nzhde
authors.initials: N
authors.lastname: Agazaryan
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
authors.forename: Michael
authors.initials: M
authors.lastname: Steinberg
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
authors.forename: Amanda
authors.initials: A
authors.lastname: Hua
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California. Electronic address: percylee@mednet.ucla.edu.
authors.forename: Percy
authors.initials: P
authors.lastname: Lee