title: Study of 201 non-small cell lung cancer patients given stereotactic ablative radiation therapy shows local control dependence on dose calculation algorithm.
abstract: OBJECTIVE
  Pencil beam (PB) and collapsed cone convolution (CCC) dose calculation algorithms differ significantly when used in the thorax. However, such differences have seldom been previously directly correlated with outcomes of lung stereotactic ablative body radiation (SABR).
  
  
  METHODS
  Data for 201 non-small cell lung cancer patients treated with SABR were analyzed retrospectively. All patients were treated with 50 Gy in 5 fractions of 10 Gy each. The radiation prescription mandated that 95% of the planning target volume (PTV) receive the prescribed dose. One hundred sixteen patients were planned with BrainLab treatment planning software (TPS) with the PB algorithm and treated on a Novalis unit. The other 85 were planned on the Pinnacle TPS with the CCC algorithm and treated on a Varian linac. Treatment planning objectives were numerically identical for both groups. The median follow-up times were 24 and 17 months for the PB and CCC groups, respectively. The primary endpoint was local/marginal control of the irradiated lesion. Gray's competing risk method was used to determine the statistical differences in local/marginal control rates between the PB and CCC groups.
  
  
  RESULTS
  Twenty-five patients planned with PB and 4 patients planned with the CCC algorithms to the same nominal doses experienced local recurrence. There was a statistically significant difference in recurrence rates between the PB and CCC groups (hazard ratio 3.4 [95% confidence interval: 1.18-9.83], Gray's test P=.019). The differences (Δ) between the 2 algorithms for target coverage were as follows: ΔD99GITV = 7.4 Gy, ΔD99PTV = 10.4 Gy, ΔV90GITV = 13.7%, ΔV90PTV = 37.6%, ΔD95PTV = 9.8 Gy, and ΔDISO = 3.4 Gy. GITV = gross internal tumor volume.
  
  
  CONCLUSIONS
  Local control in patients receiving who were planned to the same nominal dose with PB and CCC algorithms were statistically significantly different. Possible alternative explanations are described in the report, although they are not thought likely to explain the difference. We conclude that the difference is due to relative dosimetric underdosing of tumors with the PB algorithm.
authors: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida. Electronic address: Kujtim.Latifi@Moffitt.org.
authors: Kujtim
authors: K
authors: Latifi
authors: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida; Department of Physics, University of South Florida, Tampa, Florida.
authors: Jasmine
authors: J
authors: Oliver
authors: University of South Florida School of Medicine, Tampa, Florida.
authors: Ryan
authors: R
authors: Baker
authors: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida.
authors: Thomas J
authors: TJ
authors: Dilling
authors: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida.
authors: Craig W
authors: CW
authors: Stevens
authors: Department of Biostatics and Bioinformatics, Moffitt Cancer Center, Tampa, Florida.
authors: Jongphil
authors: J
authors: Kim
authors: Department of Biostatics and Bioinformatics, Moffitt Cancer Center, Tampa, Florida.
authors: Binglin
authors: B
authors: Yue
authors: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida.
authors: Marylou
authors: M
authors: Demarco
authors: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida.
authors: Geoffrey G
authors: GG
authors: Zhang
authors: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida.
authors: Eduardo G
authors: EG
authors: Moros
authors: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida.
authors: Vladimir
authors: V
authors: Feygelman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000601:surgery*; D015331:Cohort Studies; D019583:Dose Fractionation, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D008175:Lung Neoplasms / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D012306:Risk; D012984:Software; D013909:Thorax / Q000528:radiation effects*; D013997:Time Factors; D016896:Treatment Outcome