Objective To compare three- dimensional conformal radiotherapy ( 3DCRT) and intensity- modulated radiotherapy ( IMRT) in terms of their advantages of disadvantages in the treatment of primary hepatocellular carcinoma ( PHC) with portal vein tumor thrombus ( PVTT) . Methods Twenty patients with PHC accompanied by PVTT were enrolled in this study. Each patient underwent 3DCRT and IMRT with a prescribed dose of 40 Gy / 20 fractions. The parameters included the conformity index ( CI) , homogeneity index ( HI) , mean dose ( Dmean) , minimum dose ( Dmin) , maximum dose ( Dmax) , V95%, V100%, and V105% for planning target volume ( PTV) , the number of monitor units ( MUs) for evaluating planning efficiency, and Dmean, Dmax, and Dmin for the organs at risk ( OAR) . The percentage of the normal liver volume receiving ≥30, > 20, > 10, and > 5 Gy ( V30 Gy, V20 Gy, V10 Gy, and V5 Gy, respectively) were calculated to determine liver toxicity. The two radiotherapy regimens were compared in terms of the dosimetric parameters for PTV and OAR, as well as number of MUs. Results IMRT had significantly higher Dmin, Dmean, V95%, and V100% and significantly better HI and CI compared with 3DCRT ( P < 0. 05) . The liver V30 Gy and V20 Gy were 33. 55 ± 5. 67 and 44. 24 ± 6. 17, respectively, for 3DCRT, versus 29. 41 ± 2. 67 and 41. 28 ± 4. 59 for IMRT ( P = 0. 001; P = 0. 021) . There were no significant differences in liver V10 Gy, liver V5 Gy, stomach Dmax, small intestine Dmax, spinal cord Dmax, kidney Dmax, and kidney V20 Gy between IMRT and 3DCRT. The number of MUs was 303. 7 ± 35. 8 for 3DCRT and 377. 4 ± 33. 2 for IMRT ( P = 0. 000) . Conclusion IMRT provides higher tumor coverage, homogeneity, and conformity, as well as better normal liver tissue sparing, as compared with 3DCRT. However, IMRT is not superior to 3DCRT in terms of treatment efficiency.
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