A comparison of liver protection among 3-D conformal radiotherapy, intensity-modulated radiotherapy and RapidArc for hepatocellular carcinoma.

Purpose: The analysis was designed to compare dosimetric parameters among 3-D conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT) and RapidArc (RA) to identify which can achieve the lowest risk of radiation-induced liver disease (RILD) for hepatocellular carcinoma (HCC).

Methods: Twenty patients with HCC were enrolled in this study. Dosimetric values for 3DCRT, IMRT, and RA were calculated for total dose of 50 Gy/25 f. The percentage of the normal liver volume receiving >40, >30, >20, >10, and >5 Gy (V(40), V(30), V(20), V(10) and V(5)) were evaluated to determine liver toxicity. V5, V(10), V(20), V(30) and D(mean) of liver were compared as predicting parameters for RILD. Other parameters included the conformal index (CI), homogeneity index (HI), and hot spot (V(110%)) for the planned target volume (PTV) as well as the monitor units (MUs) for plan efficiency, the mean dose (D(mean)) for the organs at risk (OARs) and the maximal dose at 1% volume (D1%) for the spinal cord.

Results: The D(mean) of IMRT was higher than 3DCRT (p = 0.045). For V5, there was a significant difference: RA > IMRT >3DCRT (p <0.05). 3DCRT had a lower V(10) and higher V(20), V(30) values for liver than RA (p <0.05). RA and IMRT achieved significantly better CI and lower V(110%) values than 3DCRT (p <0.05). RA had better HI, lower MUs and shorter delivery time than 3DCRT or IMRT (p <0.05).

Conclusion: For right lobe tumors, RapidArc may have the lowest risk of RILD with the lowest V(20) and V(30) compared with 3DCRT or IMRT. For diameters of tumors >8 cm in our study, the value of Dmean for 3DCRT was lower than IMRT or RapidArc. This may indicate that 3DCRT is more suitable for larger tumors.