Author(s)

Ye Zhang¹, Yie Chen², Jie Qiu³, Jack Yang²

¹Department of Radiation Oncology, Cancer Institute and Hospital Chinese Academy Medical Sciences (CICAMS), Beijing, China.
²Department of Radiation Oncology, Monmouth Medical Center, Long Branch, USA.
³Department of Radiation Oncology, Beijing Union Hospital, Beijing, China.

Purpose: To evaluate planning quality of Stereotactic body Radiotherapy (SBRT) with multiple lungmetastases generated by the Pinnacle and Tomotherapy planning systems, respectively. Methods and Materials: Nine randomly selected patients diagnosed with non-small cell lung carcinoma with multiple lesions were planned with Philips Pinnacle (version 9.2, Fitchburg, WI) and Tomotherapy (version 4.2, Madison, WI), respectively. Both coplanar and non-coplanar IMRT plans were generated on Pinnacle system. A total dose of 60 Gy was prescribed to cover 95% of Planning Target Volume (PTV) in 3 fractions based on the RTOG0236 protocol prescription [1]. All plans with single isocenter setting were used for multiple lesions planning. A set of nine static beams were used for Pinnacle plansusing Direct Machine Parameters Optimization (DMPO) algorithm of RTOT0236 dose constraints. Planning outcomes such as minimum and mean doses, V₉₅, D₉₅ (95% of target volume receivesprescription dose), D₅, and D₁ to PTV, maximum dose to heart, esophagus, cord, trachea, brachial plexus, rib, chest wall, and liver, mean dose toliver, total lung, right and left lung, volume of chest wall receives 30 Gy, volume of lungs receives 5 Gy and 20 Gy (V₅ and V₂₀), conformity index (CI) and heterogeneity index (HI) were all reported for evaluation. Results: Mean volume of PTV was 37.77 ± 23.4 cm³. D₉₅ of PTV with Tomotherapy, coplanar, non-coplanar plan was 60.2 ± 0.3 Gy, 58.6 ± 1.2 Gy, and 59.1 ± 0.7 Gy, respectively. Mean dose to PTV was lower for Tomotherapy (p < 0.0001), so were D₅ (p < 0.0001) and D₁ (p = 0.001). CI was higher with Tomotherapyplans (p < 0.0001), so was HI (p < 0.0001). Maximum dose to other critical organs were also lower exclusively with Tomotherapy plans, as expected. Treatment time was recorded only for Tomotherapy plans (73.0 ± 20.6 min) while the Intensity Modulated Radiation Therapy (IMRT) plan from Pinnacle were not registered for comparison in those cases. Conclusions: With 51 beam angles per rotation, Tomotherapy plans could generally achieve better tumor coverage while sparing more critical structures in the multiple lung lesions study. Non-coplanar IMRT plans also have better tumor coverage with lower dose to critical organs such as lungs, liver, chest wall and cord compare to coplanar plans. Compared to the coplanar IMRT beam plans, Tomotherapy tends to have a relatively higher low dose volume in lungs such as V₅ which needs more attention for toxicity analysis.

SBRT, DMPO, Tomotherapy, Lung IMRT

Zhang, Y. , Chen, Y. , Qiu, J. and Yang, J. (2014) Dosimetric Comparisons of Lung SBRT with Multiple Metastases by Two Advanced Planning Systems. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 3, 252-261. doi: 10.4236/ijmpcero.2014.34032.