Yttrium-90 Hepatic Therapy and the Importance of Volumetric Voxel-Based Post Therapy Dosimetry: A Case Report on Renal Radiation Dose Volume Analysis with Follow Up

Abstract

This paper is a follow-up report concerning a patient treated with Yttrium-90 to a hepatocellular carcinoma. The radiation therapy dose distribution was published as a case report in 2022, https://doi.org/10.18103/mra.v10i11.3379. The hepatic target volume for directed therapy abutted the right kidney and this report provides clinical follow up information on the patient relative to renal function on unintentional radiation renal dose. Yttrium-90 therapy has become an important therapy component for patient care directed to multiple malignancies with emphasis on treating lesions in close proximity to the hepatic parenchyma. The targets are treated with an intra-arterial approach with a goal of applying target directed radiation therapy. Historically, prior to the development of voxel-based dose volume computation software, dose to target was prescribed as activity of isotope delivered with a qualitative assessment of isotope delivery based on images obtained from single positron emission computer tomography. As a qualitative image, single positron emission computer tomography served as an image reference and qualitative surrogate for representing radiation dose. Today, commercial software is available to fuse single positron emission computer tomography images into radiation oncology planning images and calculate dose to volume in a manner similar to how radiation oncology physics dosimetry teams calculate radiation dose to target volume for external therapy and brachytherapy with image guidance. In this particular case, we demonstrated that the proximity of the right kidney to the target resulted in unintentional radiation dose to renal parenchyma evaluated using voxel-based dosimetry. In this report, we review progressive decrease in renal function with blood urea nitrogen/creatinine of 45 and 2.75 respectively with continued normal liver function. Although potentially multi-factorial in origin, the decrease in renal function is at a time point consistent with radiation injury. In this paper we review radiation oncology dose volume constraints for renal tolerance and strategies for patient care moving forward. The goal is to provide additional knowledge of this issue and provide an additional knowledge layer for patient safety with emphasis on improving patient outcomes.