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内容記述 |
We compared the dose distributions of carbon-ion pencil beam scanning (C-PBS), proton pencil beam scanning (P-PBS), and VMAT for locally recurrent rectal cancer.
The C-PBS treatment planning CT datasets of ten locally recurrent rectal cancer cases were randomly selected. Three treatment plans were created using identical prescribed doses. The beam angles for C-PBS and P-PBS were identical. Dosimetry, including the dose received by 95% of the planning target volume (PTV) (D95%), dose to the 2cc receiving the maximum dose (D2cc), organ at risk (OAR) volume receiving >15Gy (V15), and >30Gy (V30), was evaluated. Statistical significance was assessed using the Wilcoxon signed-rank test.
Mean PTV-D95% values were >95% of the volume for P-PBS and C-PBS, whereas that for VMAT was 94.3%. However, PTV-D95% values in P-PBS and VMAT were <95% in 5 and 2 cases, respectively, due to the OAR dose reduction. V30 and V15 to the rectum/intestine for C-PBS (V30 = 4.2±3.2 cc, V15 = 13.8±10.6 cc) and P-PBS (V30 = 7.3±5.6 cc, V15 = 21.3±13.5 cc) were significantly lower than those for VMAT (V30 = 17.1±10.6 cc, V15 = 55.2±28.6 cc). Bladder-V30 values with P-PBS/C-PBS (3.9±4.8 Gy(RBE)/3.0±4.0 Gy(RBE)) were significantly lower than those with VMAT (7.9±8.1 Gy).
C-PBS provided superior dose conformation and lower OAR doses compared with P-PBS and VMAT. C-PBS may be the best choice for cases in which VMAT and P-PBS cannot satisfy dose constraints. C-PBS could be another choice for cases in which VMAT and P-PBS cannot satisfy dose constraints, thereby avoiding surgical resection. |
