ESTRO 2024 - Abstract Book

S2204

Clinical - Upper GI

ESTRO 2024

Department of Radiology, Bologna, Italy. 5 IRCCS Regina Elena National Cancer Institute, Nuclear Medicine Unit, Rome, Italy. 6 IRCCS Regina Elena National Cancer Institute, Department of Research and Advanced Technologies, Medical Physics and Expert Systems Laboratory, Rome, Italy

Purpose/Objective:

Selective internal radiotherapy (SIRT) is a radionuclide therapy for unresectable primary hepatocellular carcinoma (HCC) in which 90Y-loaded micron-sized embolic particles are directly injected into the hepatic arteries. The injection activity can be determined with body-surface-area (BSA) and MIRD mono-compartmental methods (both referred to as standard approach) or voxel-based dosimetry, based on a pre-treatment injection of 99mTc-macro-aggregated albumin used as a surrogate of the microspheres' distribution. The aim of this work is to perform a randomized clinical study to evaluate the impact of the two dosimetry approaches in terms of overall survival (OS).

Material/Methods:

Patients with HCC diagnosis and treated with 90Y-loaded resin microspheres at two Institutes were randomized into arm A (activity prescription based on standard approach) or arm B (activity prescription based on novel voxel-based dosimetry approach) with dose constraints based on ref.(1,2). The impact of the dosimetry approach in terms of patients' overall survival (OS) was investigated with Kaplan-Meier analysis implemented in R software. The patients' overall survival (OS) analysis for the two dosimetry approaches was investigated with Kaplan-Meier analysis with Log-rank test implemented in R software. The planned enrolment was of 150 HCC patients.

Results:

Out of 101 treatments on enrolled patients, 75 and 26 were performed on males and females, respectively. Mean(range) age was 67 years(26-97). Median(range) follow-up was 16.3 months(1-59.5). Patients were divided between arm A(50) and B(51) for which the mean(range) administered activity was 1.54(0.80-2.90) and 1.32(0.79 3.29) GBq, respectively. The OS ratio at 12 months was 63.6% and 71.9% for arm A and B, respectively, and at 24 months was 43.5% and 58.2%, respectively. Kaplan-Meier analysis showed no statistical differences (p=0.16). When the analysis was restricted to patients in which the prescribed activity differed by more than 5% between the two methods(i.e.,74 remaining patients), the OS in arm B was statistically significantly higher with respect to Arm A(p=0.041). The OS ratio at 12 months was 59.3% and 71.8% in arm A and B, respectively, and 39.5% and 62.4% at 24 months, respectively.

Conclusion:

The activity prescription based on pre-treatment voxel-based dosimetry showed a statistically significant superiority in OS compared to the standard dosimetry approach when the prescribed activity differed between the two approaches.

Keywords: radioembolisation, outcome prediction, dosimetry