Systematic review of lung shunt fraction quantification comparing SPECT/CT and planar scintigraphy for yttrium 90 radioembolization planning

Purpose Yttrium 90-labeled intra-arterial liver therapy is an effective treatment for patients with unresectable primary or metastatic liver malignancy. Optimal radioisotope dose calculation is dependent upon lung shunt fraction (LSF) which is typically estimated by planar scintigraphy. The goal of this systematic review was to compare LSF using 2D planar scintigraphy and 3D SPECT/CT. A secondary outcome was to assess the impact on lung dosimetry. Methods PubMed, SCOPUS and Web of Science database were searched for studies in English language related to lung shunt fraction quantification utilizing technetium 99m-labeled macroaggregated albumin ((99)mTc-MAA) planar scintigraphy and SPECT/CT, published between January 2010 and November 2020. The review was conducted using the PRISMA statement and QUADAS-2 criteria. Results A total of 8 studies (one prospective, 4 retrospective studies and 3 abstracts from national conferences) with a sample size of 552 were included in this review. There were 456 patients (82.6%) with hepatocellular carcinoma and 95 patients (17.4%) with hepatic metastasis. A wider range of LSF percentages was noted in planar scintigraphy methodology (range 1.2-33.3%) when compared to SPECT/CT (range 0.4-21.7%). The median LSF percentages were 6.7 and 2.9% using planar scintigraphy and SPECT/CT, respectively. Conclusion The current clinical assessment of LSF is substantially overestimated by 2D planar scintigraphy when compared to 3D SPECT/CT. However, unclearness of blinding between the index test and reference standard was an area of quality concern. Hence, further randomized or prospective studies are needed to strengthen the role of SPECT/CT in lung shunt fraction estimation.