Abstract
BackgroundTo compare the RapidArc plan for primary hepatocellular carcinoma (HCC) with 3-D conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) plans using dosimetric analysis.MethodsNine patients with unresectable HCC were enrolled in this study. Dosimetric values for RapidArc, IMRT, and 3DCRT were calculated for total doses of 45~50.4 Gy using 1.8 Gy/day. The parameters included the conformal index (CI), homogeneity index (HI), and hot spot (V107%) for the planned target volume (PTV) as well as the monitor units (MUs) for plan efficiency, the mean dose (Dmean) for the organs at risk (OAR) and the maximal dose at 1% volume (D1%) for the spinal cord. The percentage of the normal liver volume receiving ≥ 40, > 30, > 20, and > 10 Gy (V40 Gy, V30 Gy, V20 Gy, and V10 Gy) and the normal tissue complication probability (NTCP) were also evaluated to determine liver toxicity.ResultsAll three methods achieved comparable homogeneity for the PTV. RapidArc achieved significantly better CI and V107% values than IMRT or 3DCRT (p < 0.05). The MUs were significantly lower for RapidArc (323.8 ± 60.7) and 3DCRT (322.3 ± 28.6) than for IMRT (1165.4 ± 170.7) (p < 0.001). IMRT achieved a significantly lower Dmean of the normal liver than did 3DCRT or RapidArc (p = 0.001). 3DCRT had higher V40 Gy and V30 Gy values for the normal liver than did RapidArc or IMRT. Although the V10 Gy to the normal liver was higher with RapidArc (75.8 ± 13.1%) than with 3DCRT or IMRT (60.5 ± 10.2% and 57.2 ± 10.0%, respectively; p < 0.01), the NTCP did not differ significantly between RapidArc (4.38 ± 2.69) and IMRT (3.98 ± 3.00) and both were better than 3DCRT (7.57 ± 4.36) (p = 0.02).ConclusionsRapidArc provided favorable tumor coverage compared with IMRT or 3DCRT, but RapidArc is not superior to IMRT in terms of liver protection. Further studies are needed to establish treatment outcome differences between the three approaches.
Highlights
To compare the RapidArc plan for primary hepatocellular carcinoma (HCC) with 3-D conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) plans using dosimetric analysis
The typical dose distributions and dosevolume histograms (DVH) for planned target volume (PTV) and organs at risk (OAR) are shown in Figure 1 and 2, respectively
RapidArc achieved better spinal cord sparing to the 50% isodose line than did 3DCRT and IMRT
Summary
To compare the RapidArc plan for primary hepatocellular carcinoma (HCC) with 3-D conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) plans using dosimetric analysis. Most patients with HCC have unresectable disease at diagnosis These patients are treated with other treatment modalities, such as percutaneous. The use of radiation therapy (RT) for the treatment of HCC was first investigated more than 40 years ago, but the early trials reported poor results due to the low tolerance of the whole liver to radiation and severe hepatic toxicity, or radiation-induced liver disease (RILD) caused by whole liver irradiation [7,8]. The low hepatic tolerance to radiation limits the application of higher radiation doses to the tumor. As image-based treatment planning and engineering has advanced, threedimensional conformal radiotherapy (3DCRT) was developed to irradiate the tumor accurately while minimizing the dose to the normal liver. Park et al reported a significant relationship between the total dose to the liver tumor and the tumor response (< 40 Gy, 40-50 Gy, and > 50 Gy giving responses of 29.2%, 68.6%, and 77.1%, respectively) without significant toxicity (rate of liver toxicity: 4.2%, 5.9%, and 8.4%, respectively)
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