Tumor-to-normal particle deposition ratio in primary versus secondary liver malignancies: impact on tumor dose and radioembolization treatment planning

Compare hepatic tumor-to-normal particle deposition ratio (PDR) and lung shunt fraction (LSF) in patients undergoing radioembolization for primary versus secondary malignancies. Retrospective analysis was performed of all radioembolization procedures at our institution between July 2009 to February 2013. Hepatic artery technetium macroaggregated albumin (TcMAA) infusions are used for treatment planning with single-photon emission computed tomography-computed tomography (SPECT-CT) along with 3D post-processing. PDR and LSF are assessed using TcMAA particles as measurements of relative tumor vascularity and lung shunt in treatment planning for yttrium-90 radioembolization. Different cancer types are compared using Wilcoxon two-sample rank-sum tests. A total of 227 radioembolization procedures were performed. There are 121 patients with the required information for the analysis. Eleven cancer types were treated of which hepatocellular (38.8%), colorectal (30.6%), and neuroendocrine (12.4%) cancers were the majority. Mean PDR is 4.36 (SD=2.43) and median is 3.5 (range 2-19) for all cancers. The hepatocellular cancer PDR (mean 4.9, median 3.7) was significantly higher than for colorectal cancer (mean 3.5, median 3.2) (p=.012). Mean lung shunt fraction is 7.29 (SD=4.5) and median is 6.2 (range 1.3-28.5) in all cancers; there was no significant difference in LSF specifically between colorectal and hepatocellular cancers (p=0.64). Significantly higher hepatic tumor-to-normal particle deposition ratio in hepatocellular compared to colorectal cancer can result in higher tumor and lower liver dose which may impact radioembolization treatment planning. No significant difference in lung shunt fractions was observed for these two cancer types.