Abstract
Background 90Y PET/CT post-radioembolization imaging has demonstrated that the distribution of 90Y in a tumor can be non-uniform. Using computational modeling, we predicted the dosimetric impact of post-treatment 90Y PET/CT-guided percutaneous ablation of the portions of a tumor receiving the lowest absorbed dose. A cohort of fourteen patients with non-resectable liver cancer previously treated using 90Y radioembolization were included in this retrospective study. Each patient exhibited potentially under-treated areas of tumor following treatment based on quantitative 90Y PET/CT. 90Y PET/CT was used to guide electrode placement for simulated adjuvant radiofrequency ablation in areas of tumor receiving the lowest dose. The finite element method was used to solve Penne’s bioheat transport equation, coupled with the Arrhenius thermal cell-death model to determine 3D thermal ablation zones. Tumor and unablated tumor absorbed-dose metrics (average dose, D50, D70, D90, V100) following ablation were compared, where D70 is the minimum dose to 70% of tumor and V100 is the fractional tumor volume receiving more than 100 Gy.ResultsCompared to radioembolization alone, 90Y radioembolization with adjuvant ablation was associated with predicted increases in all tumor dose metrics evaluated. The mean average absorbed dose increased by 11.2 ± 6.9 Gy. Increases in D50, D70, and D90 were 11.0 ± 6.9 Gy, 13.3 ± 10.9 Gy, and 11.8 ± 10.8 Gy, respectively. The mean increase in V100 was 7.2 ± 4.2%. All changes were statistically significant (P < 0.01). A negative correlation between pre-ablation tumor volume and D50, average dose, and V100 was identified (ρ < − 0.5, P < 0.05) suggesting that adjuvant radiofrequency ablation may be less beneficial to patients with large tumor burdens.ConclusionsThis study has demonstrated that adjuvant 90Y PET/CT-guided radiofrequency ablation may improve tumor absorbed-dose metrics. These data may justify a prospective clinical trial to further evaluate this hybrid approach.
Highlights
90Y PET/CT post-radioembolization imaging has demonstrated that the distribution of 90Y in a tumor can be non-uniform
Tumor targeting in yttrium-90 (90Y) radioembolization differs from other radionuclide therapies that are infused systemically and find their targets through high affinity to cellular receptors
Patients treated with 90Y radioembolization using resin [site A, SIR-Spheres®, SIRTex Medical Ltd, North Sydney, Australia] or glass [site B, Therasphere® BTG, London, UK] microspheres for primary or secondary liver cancer and who received post-treatment 90Y PET/CT imaging were reviewed
Summary
90Y PET/CT post-radioembolization imaging has demonstrated that the distribution of 90Y in a tumor can be non-uniform. Conclusions: This study has demonstrated that adjuvant 90Y PET/CT-guided radiofrequency ablation may improve tumor absorbed-dose metrics. These data may justify a prospective clinical trial to further evaluate this hybrid approach. Like many liver-directed therapies, 90Y radioembolization is commonly classified as a palliative treatment due to the relatively poor prognosis of patients with liver cancer This does not suggest that there is no utility in treatment optimization. Response following locoregional hepatic therapy has been shown to correlate with improved patient survival, prompting the use of multimodality therapies [12, 13] to improve tumor response One such example of multimodality therapy is combined trans-arterial chemoembolization (TACE) and radiofrequency ablation (RFA) for the treatment of hepatocellular carcinoma (HCC) [12]. While multimodality treatment utilizing 90Y radioembolization has not been widely studied, several authors have attempted the use of 90Y PET/CT to provide multistage patient-specific 90Y treatments with positive outcomes [14, 15]
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