Abstract No. 341 Yttrium-90 (Y90) Radiation Lobectomy or Bi-/Tri-segmentectomy for Large Inoperable Liver Tumors

The primary objective was to evaluate the safety and efficacy of Yttrium-90 (Y90) radioembolization with ablative doses in patients with large inoperable liver tumors. Some 33 patients with large inoperable liver tumors (maximum tumor diameter 8.0±2.9 cm) were treated with Y90 ablation as second- or third-line treatment (age 73.6±9.8y, C-P score A 89%). Histology included HCC: 19, CCC: 6 and CRLM: 8. Irradiated tumor and liver volume were 274±235 mL and 980±467 mL, respectively, of 1866±561 mL whole liver volume. Delivered dose was 2.9±1.4GBq with intent for lobectomy n=19 (57%) or bi-/ tri-segmentectomy n=14 (43%). Assessed outcomes included adverse events (CTCAE v5.0), dosimetry and dose-response evaluation (MIM Software), target lesion response rates (mRECIST), liver progression-free survival and overall patient survival (OS). There were three grade 3 complications (9.0%) and no instance of REILD. Mean tumor dose was 195±163 Gy. After a median follow-up of 10 months, complete response (CR) was observed in 64% (21/33) of the irradiated tumors with an overall disease control rate of 94% (31/33). Median dose was significantly higher in CR cases (278±185 Gy) versus stable or partial response ones (137±114 Gy; p=0.0099). Median liver PFS was 7 months. Median patient OS was 11 months. Y90 ablation has an acceptable safety profile and may achieve high rates of tumor necrosis and local disease control for the treatment of large inoperable liver tumors. Mean tumor absorbed dose plays a significant role in tumor response.