Dosimetric impact of a frame-based strategy in stereotactic radiotherapy of lung tumors.
BACKGROUND
Technological innovations have taken stereotactic body radiotherapy (SBRT) from frame-based strategies to image-guided strategies. In this study, cone beam computed tomography (CBCT) images acquired prior to SBRT of patients with lung tumors was used to study the dosimetric impact of a pure frame-based strategy.


METHODS
Thirty patients with inoperable lung tumors were retrospectively analyzed. All patients had received CBCT-guided SBRT with 3 fractions of 15 Gy to the planning target volume (PTV) margin including immobilization in a stereotactic body frame (SBF). Using the set-up corrections from the co-registration of the CBCT with the planning CT, all individual dose plans were recalculated with an isocenter position equal to the initial set-up position. Dose Volume Histogram (DVH) parameters of the recalculated dose plans were then analyzed.


RESULTS
The simulated plans showed that 88% of all fractions resulted in minimum 14.5 Gy to the internal target volume (ITV). For the simulated summed treatment (3 fractions per patient), 83% of the patients would minimum receive the prescription dose (45 Gy) to 100% of the ITV and all except one would receive the prescription dose to more than 90% of the ITV.


CONCLUSIONS
SBRT including SBF, but without image guidance, results in appropriate dose coverage in most cases, using the current margins. With image guidance, margins for SBRT of lung tumors could possibly be reduced.
Department of Medical Physics, The Norwegian Radium Hospital, Oslo University Hospital, Nydalen, Oslo, Norway.
Einar
E
Waldeland
Christina
C
Ramberg
Marius Røthe
MR
Arnesen
Aslaug
A
Helland
Odd Terje
OT
Brustugun
Eirik
E
Malinen
D054893:Cone-Beam Computed Tomography; D019583:Dose Fractionation, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology* / Q000601:surgery*; D008297:Male; D011379:Prognosis; D016634:Radiosurgery; D012189:Retrospective Studies; D015996:Survival Rate