To compare the volumetric intensity modulated arc (VMAT) plan for primary hepatocellular carcinoma (HCC) with 3-dimensional conformal radiation (3DCRT) with the using dosimetric analysis.Methods
Nine patients of HCC were enrolled in this study. Total 10 lesions (one patient had bilateral lesions) measuring 1 ∼ 3 cm (median 2 cm) were analyzed. Dosimetric values for VMAT using two arcs and 3DCRT were calculated for total doses of 50 Gy using 2.5 Gy/day. The parameters included the quality of coverage (QOC), conformal index (CI), homogeneity index (HI) and hot spot (V105%) for the planning 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 liver volume receiving ≥40, >30, >20, and >10 Gy (V40 Gy, V30 Gy, V20 Gy, and V10 Gy) were also evaluated to determine liver toxicity.Results
VMAT achieved significantly better CI values (1.02 ± 0.07) than 3DCRT (1.54 ± 0.38) (P < 0.007). The MUs were significantly lower for 3DCRT (590.4 ± 108.0) than VMAT (827.7 ± 152.1) (P < 0.009). 3DCRT showed significantly better HI (1.03 ± 0.01) compared with the VMAT (1.08 ± 0.01) (P = 0.005) and target coverage result (QOC) also improved with 3DCRT (0.87 ± 0.11) compared with VMAT (0.78 ± 0.07) (P = 0.028). 3DCRT achieved a significantly better V105% values (0) than VMAT (1.25 ± 0.07) (P = 0.008). VMAT achieved a significantly lower Dmean of the liver than 3DCRT (P = 0.022). 3DCRT had higher V40 Gy, V30 Gy, V20 Gy, and V10 Gy values for the liver than did VMAT. The maximum dose to the spinal cord was not significantly different between 3DCRT (8.49 ± 5.38 Gy) and VMAT (10.98 ± 4.53 Gy) (P = 0.114).Conclusions
In patients with primary hepatocellular carcinoma, VMAT plan showed more conformal tumor coverage and an improvement in liver sparing compared with 3DCRT, whereas 3DCRT provided more homogeneous tumor coverage compared with VMAT.