LAUSR

BACKGROUND AND AIMS Pre-treatment Tc-99m MAA (MAA) scan is routinely performed prior to transarterial radioembolization (TARE) to estimate lung shunt fraction (LSF) and lung dose. In this study, we investigate LSF observed in early hepatocellular carcinoma (HCC) and provide the scientific rationale for eliminating this step from routine practice. METHODS HCC patients who underwent Y90 from (2004-2018) were reviewed. Inclusion criteria were early stage HCC (UNOS T1/T2/Milan criteria: solitary ≤5 cm, 3 nodules ≤3 cm). LSF was determined using MAA in all patients. Associations between LSF and baseline characteristics were investigated. A "no-MAA" paradigm was then proposed based on a homogenous group that expressed very low LSF. RESULTS Of 1175 Y90 HCC patients, 448 patients met inclusion criteria. Mean age was 65.6 years, 303 (68%) were males. 352 (79%) had solitary lesions, 406 (91%) unilobar disease. 243 (54%), 178 (40%) and 27 (6%) patients were Child-Pugh A, B and C, respectively. Median LSF was 3.9% (IQR: 2.4-6%). Median administered activity was 0.9 GBq (IQR: 0.6-1.4), for a median segmental volume of 170 cc (range: 60-530). Median lung dose was 1.9 Gy (IQR: 1.0-3.4). The presence of TIPS (N=38) was associated with LSF>10% (OR=16.4, CI:5.5-49.0; P<0.001). Median LSF was 3.8% (IQR: 2.4-5.7%) and 6% (IQR: 3.8-15.3%) in no-TIPS vs TIPS patients (P<0.001). CONCLUSION LSF in UNOS T1/T2 HCC without TIPS is clinically negligible. When segmental injections are planned, this step can be eliminated, thereby reducing time-to-treatment, number of procedures, and improving convenience for patients traveling from long-distances.