[Dose distributions of proton beam therapy for hepatocellular carcinoma: a comparative study of treatment planning with 3D-conformal radiation therapy or intensity-modulated radiation therapy]

Abstract

Objective: A comparative dose distribution study has been undertaken between proton beam therapy (PBT), 3-dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT) in the treatment of hepatocellular carcinoma (HCC), so as to assess the potential advantages of PBT.

Methods: Dose volume histograms (DVHs) were compared between PBT and 3D-CRT or IMRT planning at total dose of 66 Gy and 86 Gy in stage I patients (n = 10, diameter < or = 5 cm), 60 Gy and 72 Gy in stage IIA patients (n = 12, diameter = 5.1-10 cm).

Results: For patients with stage I, the mean liver dose (Dmean), V10, V20 and V30 were 13.01 Gy, 51.89%, 36.13% and 21.24% for 3D-CRT, whereas they were 6.34 Gy, 30.23%, 17.86% and 10.66%, respectively, for PBT (P < 0.002). With dose escalation to 86 Gy, the Dmean, V10, V20 and V30 were 16.91 Gy, 67.51%, 46.84% and 27.61% for 3D-CRT, whereas they were 8.26 Gy, 39.31%, 23.22% and 13.86%, respectively, for PBT (P < 0.002). Compared with 3D-CRT with dose of 66 Gy, PBT reduced the Dmean, V10, V20 and V30 even with dose escalation to 86 Gy (P < 0.042). For patients with stage IIA, the Dmean, V10, V20 and V30 were 29.18 Gy, 72.25%, 58.17%, 44.01% and 24.92 Gy, 73.32%, 56.15%, 37.75% for 3D-CRT and IMRT, respectively, with dose of 60 Gy, whereas they were 16.28 Gy, 43.93%, 33.54% and 22.78%, respectively, for PBT (P < 0.002). With dose escalation to 72 Gy, the Dmean, V10, V20, V30 were 35.02 Gy, 86.70%, 69.80%, 52.81% and 29.90 Gy, 87.98%, 67.74% and 45.30% for 3D-CRT and IMRT, respectively, whereas they were 19.54 Gy, 52.72%, 40.25% and 27.34%, respectively, for PBT (P < 0.002). Compared with 3D-CRT and IMRT with total dose of 60 Gy, PBT reduced the Dmean, V10, V20 and V30 even with dose escalation to 72 Gy (P < 0.05). In all of the 22 cases, compared with 3D-CRT, PBT reduced the doses to the nonliver OARs (organs at risks) including spinal cord, right kidney and stomach (P < 0.002). Compared with IMRT, PBT also reduced the dose to the right kidney and stomach significantly, while no significant difference was found respect to the dose to spinal cord (P > 0.05).

Conclusion: Compared with 3D-CRT, PBT reduced the dose to the normal liver tissues and nonliver OARs significantly, even with 20 to 30.3 percent of dose escalation. Compared with IMRT, PBT reduced the dose to the normal liver tissues significantly, even with 20 to 30.3 percent of dose escalation. PBT reduced the dose to the right kidney and stomach significantly. No significant difference was observed respect to the dose to spinal cord.