75 y/o F 50-PY smoker with stage IA2 (T1bN0M0) SCC of the left upper lobe


TECHNIQUE: She was treated with SBRT.

DOSE: She received 50 Gy in 5 fractions to the primary lung tumor only (per RTOG 0813).


  • IV contrast should be used for central/ultra-central lung SBRT to delineate tumor from vasculature.
  • Motion management is recommended, including 4DCT to determine tumor motion on breathing cycle.
    • If tumor motion >5mm, consider gating for treatment (often not needed for central tumors).
  • Daily imaging with cone-beam CT.
    • If available, can consider fiducial tracking.

Case contributed by National Cancer Institute / National Capital Consortium

Contours (per RTOG Lung Atlas and RTOG 0813):

GTV: Gross tumor on lung window. Fuse PET to assist.

ITV: Includes movement on 4DCT

  • Be sure to review all phases of breathing cycle (ie on 4DCT). Do NOT only contour on MIP.

CTV? No true CTV as there is no microscopic disease to treat with lung SBRT

PTV: iGTV + 5 mm


  • Central = within 2 cm of proximal bronchial tree (PBT) and/or abutting mediastinal pleura
  • Ultra-central = abutting the proximal bronchial tree
Dose/Fractionation Selection
Plan Evaluation
  • Plan should be normalized such that 100% corresponds to center of mass of PTV (typically isocenter)
  • Prescription isodose line should be chosen so that:
    • 95% of PTV is covered by Rx dose
    • 99% of PTV receives 90% of Rx dose
  • High Dose Spillage:
    • Any dose > 105% of Rx should occur within PTV
    • D105% outside PTV < 15% of PTV volume
    • Conformality ratio: V100%/VPTV ideally < 1.2, but < 1.5 acceptable.
      • Not required in small tumors < 2.5 cm axial dimension
  • Low Dose Spillage:
    • Maximum dose should be encompassed by PTV + 2 cm
    • R50%: Ratio of V50%/PTV volume ideally < 5 (PTV volume dependent)