Table 5. Digestive Tract Late Effects continued...
Hepatic complications resulting from childhood cancer therapy are uncommon and observed primarily as acute treatment toxicities. Recipients of HSCT are the exception to this rule as these individuals frequently experience chronic liver dysfunction related to microvascular, immunologic, infectious, metabolic, and toxic etiologies. Chemotherapeutic agents with established hepatotoxic potential include antimetabolite agents like 6-mercaptopurine, 6-thioguanine, methotrexate, and rarely, dactinomycin. Veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) and cholestatic disease have been observed after thiopurine administration, especially 6-thioguanine. Progressive fibrosis and portal hypertension has been reported in a subset of children who developed VOD/SOS following treatment with 6-thioguanine.[31,32,33] Acute, dose-related, reversible VOD/SOS has been observed in children treated with dactinomycin for pediatric solid tumors.[34,35] In the transplant setting, VOD/SOS has also been observed following conditioning regimens that have included cyclophosphamide/TBI, busulfan/cyclophosphamide and carmustine/cyclophosphamide/etoposide. Because high-dose cyclophosphamide is common to all of these regimens, toxic cyclophosphamide metabolites resulting from the agent's variable metabolism have been speculated as a causative factor.
Acute radiation-induced liver disease also causes endothelial cell injury that is characteristic of VOD/SOS. In adults, the whole liver has tolerance up to 30 Gy to 35 Gy with conventional fractionation, the prevalence of radiation-induced liver disease varies from 6% to 66% based on the volume of liver involved and on hepatic reserve.[37,38] Based on limited data from pediatric cohorts treated in the 1970s and 1980s, persistent radiation hepatopathy after contemporary treatment appears to be uncommon in long-term survivors without predisposing conditions such as viral hepatitis or iron overload. The risk of injury in children increases with radiation dose, hepatic volume, younger age at treatment, prior partial hepatectomy, and concomitant use of radiomimetic chemotherapy like dactinomycin and doxorubicin.[40,41,42,43] Survivors who received radiation doses of 40 Gy to at least one-third of liver volume, doses of 30 Gy or more to whole abdomen, or an upper abdominal field involving the entire liver are at highest risk for hepatic dysfunction.
Viral hepatitis B and C may complicate the treatment course of childhood cancer and result in chronic hepatic dysfunction. Hepatitis B tends to have a more aggressive acute clinical course and a lower rate of chronic infection. Hepatitis C is characterized by a mild acute infection and a high rate of chronic infection. The incidence of transfusion-related hepatitis C in childhood cancer survivors has ranged from 5% to 50% depending on the geographic location of the reporting center.[45,46,47,48,49,50,51] Chronic hepatitis predisposes cirrhosis, end-stage liver disease, and hepatocellular carcinoma. Concurrent infection with both viruses accelerates the progression of liver disease. Since the majority of patients received some type of blood product during childhood cancer treatment and many are unaware of their transfusion history, screening based on date of diagnosis/treatment is recommended unless there is absolute certainty that the patient did not receive any blood or blood products. Therefore, all children who received blood transfusions before 1972 should be screened for hepatitis B and before 1993 should be screened for hepatitis C virus and referred for discussion of treatment options.