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Dosimetric Advantages of Proton and Carbon Ion Therapy for Treatment of Retroperitoneal Liposarcoma

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J Sun*, K Shahnazi , W Wang , Y Sheng , Q Zhang , Shanghai Proton and Heavy Ion Center, Shanghai, China


SU-I-GPD-T-164 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To explore the dosimetric benefits of proton and carbon ion therapy versus photon therapy for the treatment of a retroperitoneal liposarcoma case.

Methods: A recurrent case of liposarcoma of kidney (target size: 8cm*5 cm*6 cm) after surgical resections (in 2010 and 2011) was studied. The prescribed dose was 48 Gy(RBE) in 16 Fx to CTV and 21 Gy(RBE) in 7 Fx to CTVboost using sequential mode. For particle therapy, two proton plans and two carbon ion plans were separately made with one plan targeting CTV and the other plan targeting CTVboost. For photon therapy, two plans using arced IMXT (ARC) and another two plans using fixed field IMXT (FF) were also made similar to target assignment of particle beams. The doses distributions for these four sets of plans were exported to MIM software. Dose volume histograms (DVHs) were graphed and compared.

Results: The mean dose of the CTV from the different plans were similar which were 65.13 Gy(RBE), 65.04 Gy(RBE), 64.99 Gy(RBE) and 64.95 Gy(RBE) for the ARC, FF, proton and carbon ion plans respectively. DVHs of all critical organ at risks (OARs) showed significant difference between proton therapy, carbon ion therapy and photon therapy. In proton and carbon ion plans, V45 of duodenum were far better than FF or ARC modalities. The max dose of spinal cord was 33.52 Gy(RBE), 35.15 Gy(RBE), 6.66 Gy(RBE) and 0.69 Gy(RBE) for the ARC, FF, proton and carbon ion plans respectively. There were almost no dose in the left kidney. But for ARC or FF, the max dose were 9.55 Gy(RBE) and 8.73 Gy(RBE) respectively.

Conclusion: Proton and carbon ion therapy showed many advantages in retroperitoneal liposarcoma cases comparing with x ray therapy.

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