Clinical Impact of 99mTc-MAA SPECT/CT-based Personalized Predictive Dosimetry in Selective Internal Radiotherapy: a Retrospective, Single-center Study for Unresectable HCC Patients

BackgroundRecent data indicates that personalized dosimetry-based selective internal radiotherapy (SIRT) may be associated with better outcome for unresectable hepatocellular carcinoma (HCC).AimWe aim to evaluate the contribution of personalized predictive dosimetry (performed with Simplicity90® software) in HCC patients by comparing them to our historical cohort whose activity was determined by standard dosimetry. MethodsThis is a retrospective, single-center study conducted between February 2016 and December 2020 that included patients with HCC who received SIRT after simulation based on either standard dosimetry (group A) or, as of December 2017, on personalized dosimetry (group B). Primary objectives were best overall response (BOR) and objective response rate (ORR) evaluated by mRECIST at 3 months. Safety and toxicity profiles were evaluated at day 1, 1- and 3-months post-treatment. For group A we studied the dose-response relationship at 3 months and compared the activity to be administered determined a posteriori using Simplicit90Y® and the activity actually administered determined by the standard approach.ResultsBetween February 2016 and December 2020, 66 patients received 69 simulations leading to 40 treatments. The median follow-up time was equal for both groups, 21 months (range 3-55) in group A and 21 months (range 4-39) in group B. The per patient analysis revealed a significant benefit of personalized predictive dosimetry in terms of better overall response at 3 months (80% vs. 33.3%, p= 0.007) and at 6 months (77.8% vs. 22.2%, p= 0.06). This trend was found in the analysis by nodule with a response rate according to mRECIST of 87.5% for personalized dosimetry versus 68.4% for standard dosimetry at 3 months, p= 0.24. Only one grade 3 biological toxicity (hyperbilirubinemia) was noted in group A. The comparison between the administered activity and the recommended activity recalculated a posteriori using Simplicit90Y® showed that the vast majority of patients who progressed (83.33%) received less activity than that recommended by the personalized approach or an inadequate distribution of the administered activity. ConclusionsOur study confirms that the use of personalized dosimetry allows a better selection of HCC patients who can benefit from SIRT, and consequently, improves the effectiveness of this treatment.