Liver
Radiation Therapy (RT) Toxicity
Radiation induced liver disease usually:
- Presents in the first 12 weeks after completion of RT
- Resembles VOD/SOS resulting from endothelial cell injury.
RT Tolerance:
Radiation induced liver damage can occur with doses of 30 Gy to 40 Gy to the entire liver, but significantly higher doses to focal volumes can be given with few clinical complications.
Lower doses can be associated with liver disease if the child is also receiving concurrent chemotherapy which sensitizes the liver.
- Pediatric hepatic RT dose limits are not clearly defined.
- In adults
- The whole liver has tolerance up to 30–35 Gy (conventional fractionation)
- Prevalence of RT induced liver disease varies from 6% to 66% (based on the volume of liver involved and on hepatic reserve).
- Smaller volumes of liver may be safely given RT to higher doses, while accounting for the radio-sensitizing effects of chemotherapy.
RT induced liver disease has been studied in children with Wilms tumor, neuroblastoma, and hepatoblastoma. The risk of injury is increased with:
- RT dose
- Volume of liver in the treatment field
- High risk of chronic liver problems in survivors who were given:
- RT doses of 40 Gy to at least one third of liver volume
- Doses of 30 Gy to whole abdomen
- Upper abdominal field involving the entire liver
- Younger age at treatment
- Prior partial hepatectomy
- Concomitant use of radiomimetic chemotherapy like dactinomycin and doxorubicin
Also some other conditions predispose patients to have persistent radiation hepatopathy such as viral hepatitis or iron overload.
It is very unusual to find persistent liver problems in patients treated more recently - but the length of follow up is short.
The evidence for a clear association of secondary hepatic malignancies within the radiation field is limited, but RT increases the risk of a solid secondary malignancy.
More recent improved RT planning techniques such as three dimensional (3D) planning give more accurate treatment to tumors and spare normal liver. Long-term outcome of liver function following contemporary technology are not yet available.
