Comparison of dose distributions when using carbon ion radiotherapy versus intensity-modulated radiotherapy for hepatocellular carcinoma with macroscopic vascular invasion: A retrospective analysis

Abstract

Background. Studies comparing the dose distributions of carbon ion radiotherapy (C-ion RT) and intensity-modulated radiotherapy (IMRT) in patients with locally advanced hepatocellular carcinoma (LAHCC) are lacking. This study aimed to investigate the dose distributions of these modalities and identify any advantages to using C-ion RT. Methods. Patients with LAHCC who had undergone C-ion RT between June 2010 and November 2018 were retrospectively analyzed. From among 210 patients with hepatocellular carcinoma who received C-ion RT, 10 consecutive patients with LAHCC were included. The dose-volume histogram parameters of clinical plans using C-ion RT at 60 Gy (relative biological effectiveness [RBE]) and simulated plans using IMRT at 60 Gy and 50 Gy were compared. We evaluated the three plans in terms of the following parameters: the percentage of the minimum dose that covered 95% of the target volume (D95); mean liver dose (MLD); and percentage of the normal liver volume that received at least 5 Gy (V5), 10 Gy (V10), 20 Gy (V20), 30 Gy (V30), 40 Gy, and 50 Gy. Patients at high risk of developing radiation-induced liver disease (RILD) were those with MLD and V30 of >23 Gy and >28%, respectively. Results. The V5, V10, V20, and MLD were significantly lower in patients who received 60 Gy (RBE) of C-ion RT than in those who received 60 Gy of IMRT, although the D95 values were not significantly different. The V5, V10, and V20 were also significantly lower in patients who received 60 Gy (RBE) of C-ion RT than in those who received 50 Gy of IMRT; moreover the D95 was significantly superior in the former group. The numbers of high-risk patients who developed RILD when administered 60 Gy (RBE) of C-ion RT, 60 Gy of IMRT, and 50 Gy of IMRT were 1, 7, and 6, respectively. Conclusions. C-ion RT exhibits a better dose distribution to the liver than does IMRT when treating patients with LAHCC. C-ion RT made it possible to treat patients with LAHCC who otherwise could not be treated using IMRT because of the high risk of RILD.

Clinical impact of Hypofractionated carbon ion radiotherapy on locally advanced hepatocellular carcinoma

“…This result suggested that high-dose C-ion beam administration can achieve local control, which may result in long-term local recurrence-free survival. Previous studies compared DVH for tumorous and normal liver between C-ion RT and X-ray RT (SBRT and IMRT) [10,11]. Particularly for LAHCC, which is a large tumor or/ and a tumor with irregular shapes, the dose required for the normal liver may be higher than that used for HCC, which has no macroscopic vascular invasion.…”

“…Carbon ion radiotherapy (C-ion RT) provides both, physical and biological advantages over X-ray RT, and several researchers have shown favorable clinical outcomes in HCC patients when they were treated with C-ion RT [ 6 – 9 ]. In the physical aspect, previous studies have demonstrated a dose distribution advantage, showing that a reduced dose was delivered to the liver using C-ion RT compared with those of stereotactic body RT (SBRT) and intensity-modulated RT (IMRT) [ 10 , 11 ]. This was achieved owing to the physical nature of the C-ion RT procedure with distal tail-off due to the Bragg Peak and a sharp lateral penumbra [ 12 ].…”

Clinical Impact of Hypofractionated Carbon Ion Radiotherapy on Locally Advanced Hepatocellular Carcinoma

“…This result suggested that high-dose C-ion beam administration can be made local control, which may result in long-term recurrence-free area at the irradiated site. Previous studies compared DVH for tumorous and normal liver between C-ion RT and X-ray RT (SBRT and IMRT) [10,11]. Speci cally, for LAHCC, which is a large tumor or/and a tumor with irregular shapes, the dose required for the normal liver might be higher than that used for HCC, which has no macroscopic vascular invasion.…”

“…Yoon et al showed that TACE combined with X-ray RT resulted in improved prognosis compared with molecular targeted therapy alone [5]. In terms of dose distribution, C-ion RT showed higher dose concentration than X-ray RT [10,11]; therefore, C-ion RT can result in the reduced dose distributed to the healthy liver region without reducing the dose delivered to the tumor, and thereby preserve liver function. If liver function can be preserved, the numbers of treatment options for preventing HCC recurrence may be increased.…”

Clinical Impact of Hypofractionated Carbon Ion Radiotherapy on Locally Advanced Hepatocellular Carcinoma

“…showing that a reduced dose was delivered to the liver in C-ion RT compared with that in stereotactic body RT (SBRT) and intensity-modulated RT (IMRT) [10,11]. This was achieved owing to the physical nature of the C-ion RT procedure with distal tail-off due to the Bragg Peak and a sharp lateral penumbra [12].…”