(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: SBRT has become the preferred treatment method for inoperable patients with early-stage central lung tumors.For lung metastatic tumors, however, there are few guidelines to evaluate the quality of SBRT plans. This report evaluates the target volume of lung metastatic tumors SBRT using RTOG-0813 criteria.
Methods: 88 lesions in 80 patientes are treated with SBRT in our center were enrolled in this study with 50 Gy/5fx(20%), 60 Gy/10fx(21%), 64 Gy/8fx(51%), other fractionation(8%) prescription. ITVs were delineated on MIP images generated by 4D-CT. PTV volumes ranged from 3.53 to 185.29 cc(mean = 45.49±39.72 cc). OARs were delineated on average images. Optimal SBRT plans were generated using coplanar FF-IMRT beams. All plans are using 6 MV-SRS energy.
Results: All organs at risk met the dose limits in RTOG 0813, all plans have target dose coverage 96% of target volume receive 100% prescription dose. 6-10 beam angles are used in planning. The average CI numbers are 1.16 ± 0.10, The average GI number is 5.16, 5.09, 4.97, 4.71, 4.55, 4.51, 4.13 when target volume is less than 13.2 cm2, from 13.2 cm2 to 22.0 cm2, 22.0 cm2 to 34.0 cm2, 34.0 cm2 to 50.0 cm2, 50.0 cm2 to 70.0 cm2 ,70.0 cm2 to 95.0 cm2 and larger than 95 cm2. The HI numberhave a mean value of 0.82 ± 0.05. the D2 cm numbers are ranging from 47% to 87%. 82 out of 88 plans have the 105% of prescription dose volume outside target are less than 15% of the target volume.
Conclusion: The RTOG 0813 dosimetric compliance criteria can be used for evaluate Stereotactic Body Radiation Therapy for lung metastatic tumors. Some plans’ CI,GI,HI numbers have major or minor deviations because of the adjacent OARs or large target volume. Further investigations and clinical results is recommended for evaluation of clinical outcomes.
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