Reducing the probability of radiation-induced hepatic toxicity by changing the treatment modality from helical tomotherapy to fixed-beam intensity-modulated radiotherapy.

Jin Ho Song,Seok Hyun Son,Hong Seok Jang,Chul Seung Kay

doi:10.18632/oncotarget.5581

Abstract

To estimate and compare the risk of radiation-induced hepatic toxicity (RIHT) in helical tomotherapy and fixed-beam intensity-modulated radiotherapy (IMRT) for the treatment of hepatocellular carcinoma (HCC). Twenty patients with unresectable HCC treated with tomotherapy were selected. We performed tomotherapy re-planning to reduce the non-target normal liver volume receiving a dose of more than 15 Gy (NTNL-V15Gy), and we created a fixed-beam IMRT plan (FB-P). We compared the dosimetric results as well as the estimated probability of RIHT among the tomotherapy initial plan (T-IP), the tomotherapy re-plan (T-RP), and the FB-P. Comparing the T-RP and FB-P, the homogeneity index was 0.11 better with the T-RP. However, the mean NTNL-V15Gy was 6.3% lower with the FB-P. These differences result in a decline in the probability of RIHT from 0.216 in the T-RP to 0.115 in the FB-P. In patients whose NTNL-V15Gy was higher than 43.2% with the T-RP, the probability of RIHT markedly reduced from 0.533 to 0.274. By changing the treatment modality from tomotherapy to fixed-beam IMRT, we could reduce the liver dose and the probability of RIHT without scarifying the target coverage, especially in patients whose liver dose is high.

Highlights

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and it is known as the third most common cause of cancer death [1]
The mean non-target normal liver (NTNL)-volume receiving ≥ 15 Gy (V15Gy) was 6.3% lower with the fixed-beam IMRT plan (FB-P). These differences result in a decline in the probability of radiation-induced hepatic toxicity (RIHT) from 0.216 in the tomotherapy re-plan (T-RP) to 0.115 in the FB-P
In patients whose NTNL-V15Gy was higher than 43.2% with the T-RP, the probability of RIHT markedly reduced from 0.533 to 0.274

Summary

Introduction

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and it is known as the third most common cause of cancer death [1]. Complete resection is still recognized as the most effective treatment in early-stage disease. Several alternative treatment modalities, such as transarterial chemoembolization, percutaneous ethanol injection, radiofrequency ablation, and radiotherapy have been used in these patients [3]. The role of radiotherapy in HCC patients was limited because of the poor tolerance of the whole liver to radiation [4]. Several clinical and dosimetric parameters have been suggested for predicting the development of radiation-induced hepatic toxicity (RIHT), because the toxicity to the liver is the greatest impediment to improving clinical outcomes [4, 12,13,14,15,16,17,18,19]

Methods

Results

Conclusion