Volumetric intensity-modulated Arc (RapidArc) therapy for primary hepatocellular carcinoma: comparison with intensity-modulated radiotherapy and 3-D conformal radiotherapy

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.

A fixed-jaw method to protect critical organs during intensity-modulated radiotherapy

“…The PTV was evaluated using the following parameters: the conformity index (CI) and the homogeneity index (HI), defined in Ref. 13. CI represents the dose fit of the PTV relative to the volume covered by the prescribed isodose lines, which is defined as follows:…”

Consensus for Radiotherapy in Hepatocellular Carcinoma from The 5th Asia-Pacific Primary Liver Cancer Expert Meeting (APPLE 2014): Current Practice and Future Clinical Trials

“…Through strict dose constraints according to the method of inverse planning, IMRT permits more conformal and higher dose delivery in HCC [40,41]. Dose escalation of RT with IMRT has been achieved without significant incremental toxicity and has delivered better survival compared with 3D-CRT, which have been verified in several studies [42,43].…”

Transcatheter Arterial Chemoembolization Plus131I-Labelled Metuximab versus Transcatheter Arterial Chemoembolization Alone in Intermediate/Advanced Stage Hepatocellular Carcinoma: A Systematic Review and Meta-Analysis

“…RT for HCC has traditionally not been used because older techniques fail to adequately localize the radiation to the tumor. However, recent improvements in RT have allowed increased intra-tumor radiation and decreased radiation to the adjacent normal liver and organs, thereby reducing the rate of adverse events (26). …”