Feasibility of helical tomotherapy in stereotactic body radiation therapy for centrally located early stage non‒small-cell lung cancer or lung metastases.
OBJECTIVE
To investigate the ability of helical tomotherapy (HT) to spare critical organs immediately adjacent to the tumor target in stereotactic body radiation therapy (SBRT) for centrally located lung lesions.


METHODS
HT SBRT plans for 10 patients with centrally located lesions or lesions immediately adjacent to a critical structure were generated. A total of 70 Gy in 10 fractions was prescribed to the planning target volume (PTV) to satisfy a target volume coverage of ≥95% PTV receiving 70 Gy and an established set of dose constraints for the organs at risk (OARs). Quality assurance (QA) of the HT plans was performed with both ion chamber and film measurements.


RESULTS
The PTV coverage criteria was met with 95% of the PTV receiving 70.68 ± 0.33 Gy for all cases even though the OARs immediately adjacent to the PTV ranged from 0.38 to 0.85 cm away. The mean lung dose (MLD), and V(20) were 7.15 ± 1.44 Gy, and 11.93 ± 3.24 % for the total lung, respectively. The dose parameters of MLD, V(5), V(10), and V(20) for the contralateral lung were significantly lower than those for the ipsilateral lung (p < 0.05). An average dose fall off from the PTV periphery to the edge of the immediately adjacent OAR was 47.6% over an average distance of 4.87 mm. Comparison of calculated and measured doses with the ion chamber showed an average of 1.85% point dose error, whereas an average mean gamma and the area with a gamma larger than 1 of 0.20 and 0.94% were observed, respectively.


CONCLUSIONS
HT allows the sparing of critical structures immediately adjacent to the tumor target, thus making SBRT for these centrally located lesions feasible.
Department of Radiation Oncology, the University of Arizona, Tucson, AZ 85724-5081, USA. achiaz2010@gmail.com
Alexander
A
Chi
Si Young
SY
Jang
James S
JS
Welsh
Nam P
NP
Nguyen
Evan
E
Ong
Lisa
L
Gobar
Ritsuko
R
Komaki
D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D005240:Feasibility Studies; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000556:secondary / Q000601:surgery*; D009367:Neoplasm Staging; D058958:Organs at Risk / Q000033:anatomy & histology / Q000528:radiation effects*; D011859:Radiography; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D047368:Tumor Burden