Do we still need to assess for lung shunt in all Y90 Liver treatment’s ?

Introduction: Since the introduction of transarterial radioembolization (TARE) for the treatment of liver malignancies a key pre therapy step has been to assess for potential lung shunting with a hepatic arterial injection of Tc-MAA and a quantitative image assessment of the radiopharmaceutical distribution. However this causes the need for additional costs and morbidity as well as a treatment delay. Literature and our experience has suggested that a critical evaluation of the cross sectional imaging prior to therapy may help predict when significant shunting to the lungs may be present. We wanted to evaluate which imaging findings were key for prediction of significant lung shunting.

Methods: We retrospectively evaluated 823 lung shunt studies performed at our institution over a 7 year period and identified those with a substantial lung shunt (>/= 15%). We then evaluated the pre-treatment cross sectional imaging for the type, size, number and location of liver tumors, as well as for the presence of vascular tumor involvement.

Results: Of the 823 studies only 58 (7%) had significant (>15%) lung shunting. Of these, 45 (76%) were primary liver tumors, most were hepatocellular carcinoma with only one cholangiocarcinoma. The rest 13 (24%) were metastatic disease with neuroendocrine the dominant type (46%). Tumor size larger than 10 cm was seen in 24 (41%) and greater than 7cm seen in 30 (52%). In the smaller tumor group 38 ( <7cm), multiple lesions/diffuse disease was seen in 11 (29%), vascular pathology in 6 (16%) and poor location , such as segment one, was noted in 6 (16%). In the majority of cases of significant shunting, abnormal vascular shunting was also noted on the angiography images.Discussion:As we have seen the presence of significance of lung shunting is overall very low. Additionally, there are key predictive factors on the cross sectional imaging, such as tumor size and vascular pathology which can predict its likelihood. There are also predictive findings for significant shunting noted on the angiographic images. Therefore it is not clear if lung shunting evaluation is therefore warranted in every case of TARE, especially if there is an increased awareness of these predictive factors.