Liver-sparing total body irradiation using helical tomotherapy

Purpose: Liver toxicity is a possible complication of hematopoietic stem cell transplantation (HSCT) and conditioning. This problem is magnified for patients with hepatic parenchymal disease. In this context, we present the first case of liver-sparing total body irradiation (TBI) utilizing helical tomotherapy.

Methodology: A 23-year-old male with relapsed Pre-B cell acute lymphoblastic leukemia presented for evaluation for myeloablative TBI prior to allogeneic HSCT. During evaluation, he was found to have elevated liver transaminases. Subsequent workup revealed evidence of parenchymal liver disease from iron overload, which was then appropriately treated. After multi-disciplinary discussion, the decision was made to proceed with liver-sparing TBI prior to HSCT to potentially reduce the risks of complications.
The treatment plan was separated into upper and lower body regions, with a planning target volume (PTV) delineated to cover the entire body plus a 5 mm margin to ensure adequate dose coverage. The liver was excluded from the PTV, and a blocking technique was implemented to restrict beam entry into the liver during treatment planning. A dynamic jaw with a field width of 5 cm and a pitch value of 0.397 were utilized.
The prescription dose was 12 Gy delivered in eight fractions, administered twice daily over four consecutive days, with HSCT scheduled the day after TBI completion.

Results: The patient successfully underwent liver-sparing TBI and HSCT . The liver, with a size of 1616 cc, received a maximum dose of 11.09 Gy and a mean dose of 5.98 Gy. The patient was placed on defibrotide for veno-occlusive liver disease prophylaxis during his hospital stay. His post-transplantation course was complicated by graft versus host disease and pancytopenia. However, the patient’s most recent follow up 153 days after HSCT revealed no evidence of disease with only mildly elevated transaminases.

Conclusions: Liver-sparing TBI is feasible and deliverable using helical tomotherapy in patients requiring TBI as part of a HSCT conditioning regimen.

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