How Common Are Hepatopulmonary Shunts in Patients With Metastatic Neuroendocrine Tumors?

AUSTIN, TX—Patients with metastatic neuroendocrine tumors may potentially be able to consider same-day mapping or no mapping prior to treatment with Y-90 radioembolization, based on the rare incidence of hepatopulmonary shunting in this population. Researchers presented their data in an abstract presentation at the Society of Interventional Radiology.

Although there is abundant literature on treatment of hepatopulmonary shunts in metastatic colorectal cancer and hepatocellular carcinoma, few studies have analyzed hepatopulmonary shunting in metastatic neuroendocrine tumors. The authors undertook their study to better understanding shunting in this population and how it could affect the decision to recommend mapping prior to Y-90 radioembolization.

The study, which was based on a retrospective analysis, took place at 2 high-volume centers and involved 99 patients between 2009 and 2018 with neuroendocrine tumors who underwent Tc-99m imaging. The hepatic territory was injected with 5 mCi of Tc-99m macroaggregated albumin, after which plantar anterior and posterior views of the chest and abdomen were obtained. The ratio of lung-counts to total-counts in the liver and lung was used to calculate lung shunt fraction.

Of the 99 patients included in the study, 1 patient with metastatic PNET with bone involvement had a lung shunt fraction greater than 20% and could not be treated with radioembolization. There were two patients who needed dose reduction during radioembolization as a result of lung shunt fraction between 15% and 20%. Median lung shunt fraction among the patients in the study was 3%. Additionally, the authors observed no significant difference between lung shunt fraction in right versus left lobar mapping.

The study’s limitations include its retrospective design, with data collection ongoing, as well as potential selection bias of patients who underwent mapping. Tumor grade was not assessed, and many patients underwent variable systemic treatment regimens.

“The incidence of hepatopulmonary shunting in patients with metastatic neuroendocrine tumors is rare. This data helps in the counseling of patients with neuroendocrine tumors seeking radioembolization, and supports either same-day Tc-99m mapping and Y90 therapy, or potentially forgoing Tc-99m evaluation, as viable treatment paradigms in this patient group,” the authors wrote.

—Lauren LeBano

Reference

Kim J, Watchmaker J, Gruener J, et al. Incidence of hepatopulmonary shunting in patients with metastatic neuroendocrine tumors: multicenter experience. Abstract #234. Society of Interventional Radiology. Presented March 25, 2019.