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Purpose: Stereotactic body radiation therapy SBRT has emerged as a standard treatment modality for medically inoperable early-stage lung cancer patients. The aim of this paper is to calculate radiobiological parameters for a sample of 39 patients who underwent lung SBRT. Materials and Methods: For SBRT, a typical regimen of 50 Gy in 4 - 5 fractions results in local tumor control rates around 99.9%. We calculate dose volume histograms DVHs of targeted tumors and organs at risk for 39 patients. All patients received 4D imaging, and their internal treatment volumes ITVs were created by phase-based sorting of multiple CT datasets. Planning target volume PTV diameters ranged from 2.0 to 5.7 cm. The DVHs for the PTV and organs at risk were analyzed using a Biosuite algorithm to calculate the equivalent uniform dose EUD, tumor control probability TCP via a Poisson model, and normal tissue complication probability NTCP via an LKB model. The radiobiological effects were analyzed by correlating EUD and TCP with PTV volumes. Results: The mean PTV volume was 31.60 ± 25.55 cc. The mean EUDs were 5.19 ± 2.84, 5.66 ± 4.95, 61.45 ± 29.18, 3.31 ± 5.92, 6.45 ± 5.18, and 12.22 ± 5.94 Gy for lungs, spinal cord, chest-ribs, heart, esophagus, and skin, respectively. On average, the heart had the lowest EUD and the chest-ribs had the highest 61.45 ± 29.18 Gy. The mean NTCPs were estimated at 3.75% ± 2.61%, 36.25% ± 36.42%, and 0.59% ± 1.48%, for the lungs, chest and esophagus, respectively. The NTCPs of spinal cord, heart, and skin were 0.00%. The mean TCP value was 99.72% ± 0.44%. The mean BED value for our study was 109.49 Gy. Conclusions: We have calculated radiobiological predictors based on DVHs for early-stage non-small cell lung cancer via SBRT. Our calculated predictors are compatible with previously published SBRT reports.

KEYWORDS

BED, EUD, NSCLC, NTCP, TCP, SBRT

Cite this paper

Gloi, A. 2016 Lung SBRT through Radiobiology. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 5, 78-87. doi: 10.4236-ijmpcero.2016.51008.





Autor: Aime M. Gloi

Fuente: http://www.scirp.org/



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