Dose as a function of lung volume and planned treatment volume in helical tomotherapy intensity-modulated radiation therapy-based stereotactic body radiation therapy for small lung tumors.
OBJECTIVE
To evaluate the limitations of Hi-Art Helical Tomotherapy (Middleton, WI) stereotactic body radiotherapy (SBRT) for lung lesions, and to provide an initial report on patients treated with this method. Stereotactic body radiotherapy was shown to be an effective, well-tolerated treatment for early-stage, non-small-cell lung carcinoma (NSCLC). The Radiation Therapy Oncology Group (RTOG) 0236 protocol is currently evaluating three-dimensional conformal SBRT that delivers 60 Gy in three fractions.


METHODS
Inverse treatment planning for hypothetical lung gross tumor volumes (GTV) and planned treatment volume (PTV) expansions were performed. We tested the hypothesis that the maximum acceptable dose (MAD) to be delivered to the lesion by SBRT could be predicted by PTV and lung volume. Dose constraints on normal tissue were as designated by the RTOG protocol. Inverse planning was performed to find the maximum tolerated SBRT dose up to 60 Gy.


RESULTS
Regression analysis of the data obtained indicated a linear relationship between MAD, PTV, and lung volume. This generated two equations which may be useful predictive tools. Seven patients with Stage I and II NSCLC treated at the University of Virginia with this method tolerated the treatment extremely well, and suffered no greater than grade I toxicity, with no evidence of disease recurrence in follow-up from 2-20 months.


CONCLUSIONS
Helical tomotherapy SBRT for lung lesions is well-tolerated. In addition, the likely MAD for patients considered for this type of treatment can be predicted by PTV and lung volume.
Baisden
Joseph M
JM
Department of Radiation Oncology, University of Virginia Health System, Charlottesville, VA 22908, USA.
Romney
Davis A
DA
Reish
Andrew G
AG
Cai
Jing
J
Sheng
Ke
K
Jones
David R
DR
Benedict
Stanley H
SH
Read
Paul W
PW
Larner
James M
JM
D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D020714:Maximum Tolerated Dose; D055585:Physical Phenomena; D010825:Physics; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012044:Regression Analysis; D036542:Tomography, Spiral Computed; D047368:Tumor Burden