New frontiers in radioembolization

Abstract

Radioembolization is a locoregional transarterial therapy that combines radionuclide and micron-sized beads to deliver radiation internally to the target tumors based on the arterial blood flow. While initially developed as a palliative treatment option, radioembolization is now used for curative intent treatment, neoadjuvant therapy, and method to downstage or bridge for liver transplant. Radioembolization has become increasingly utilized and is an important therapeutic option for the management of hepatocellular carcinoma and liver metastasis. This article provides an overview of the techniques, challenges, and novel developments in radioembolization, including new dosimetry techniques, radionuclides, and new target tumors.

Keywords: dosimetry; eye90; holmium; radioembolization; selective internal radiation therapy.

Figure 1.

⁹⁰Y segmentectomy. (a) Axial CT shows solitary colorectal metastatic disease that is too large for successful ablation. (b) Angiogram reveals a larger disease burden than expected, affecting two segments. (c) CBCT obtained during angiogram and used to accurately calculate volumes for dose calculations. (d) SPECT/CT after Tc99-MAA administration. (e) Post ⁹⁰Y SPECT; a 200 Gy dose was calculated and delivered to segments 5 and 8 (resin). (f) Axial CT shows interval decrease in size of tumor post ⁹⁰Y. CBCT, cone-beam CT; CT, computed tomography; SPECT, single-photon emission computed tomography; Tc-MAA, ^99mTechnetium-macroaggregated albumin.

Figure 2.

⁹⁰Y Lobar radioembolization. (a) Pre ⁹⁰Y radioembolization planar PET/CT demonstrates the extent of colorectal metastatic disease in the liver. (b) Pre-⁹⁰Y radioembolization axial fused PET/CT shows active metastasis in both lobes. (c) Axial fused SPECT Tc99-MAA shows delivery of Tc99-MAA particles in both lobes on mapping/shunt study. (d) Coronal planar SPECT study shows ⁹⁰Y delivery to the left hepatic lobe. (e and f) Axial fused SPECT post ⁹⁰Y demonstrates ⁹⁰Y delivery to the left hepatic lobe after the first session (e) and right hepatic lobe on the follow up session (f); 110 Gy dose delivered to the tumor. (g) 10-Month post-treatment PET/CT shows a good response (e.g., no hypermetabolic disease). CT, computed tomography; PET, positron emission tomography; SPECT, single-photon emission computed tomography; Tc-MAA, ^99mTechnetium-macroaggregated albumin.

Figure 3.

Radioembolization using Eye90 microsphere. (a) Baseline MRI shows a focal HCC measuring 3.5 × 2.1 cm. (b) Post-procedure CT shows radiopacity of spheres in the tumor. (c) Post-SPECT CT of treated tumor with 0.8 GBq. (d) 3-Month post-treatment CE CT reveals no tumor enhancement. (e) 3-Month post-treatment CE MRI shows 1.3 × 1.5 cm density, corresponding to complete response by mRECIST criteria. (f–h) CT dosimetry with (i) corresponding dose color map legend. (j) SPECT with (k) corresponding dose color map legend. (l) SPECT CT shows proper deposition of Eye90 within the target tumor. CE, Conformitè Europëenne; CT, computed tomography; HCC, hepatocellular carcinoma; MRI, magnetic resonance imaging.

Figure 4.

Voxel base dosimetry. A 65-year-old female with a history of prior malignancy presenting with unresectable newly diagnosed biopsy-proven right liver hepatocellular carcinoma. (a) MRI shows arterially enhancing mass on post-contrast T1 weighted image (panel and (b) in room hybrid CT. (c) Arteriogram shows hypervascular mass supplied by right hepatic artery, followed by radioembolization using Flex-3 resin ⁹⁰Y microspheres (SIRTEX Medical, Woburn, MA, USA). (d–f) Post-⁹⁰Y administration SPECT-CT confirmed target embolization of the tumor with high uptake, and dosimetry demonstrated a mean and maximum tumor dose of about 500 and 1300 Gy, respectively. (g–i) Voxel-based dosimetry highlights the differential absorbed dose in the tumor displayed as a percentage of the maximum tumor dose (displayed using rainbow colors) with highest absorbed dose in the tumor center compared to the lowest in the margin. CT, computed tomography; MRI, magnetic resonance imaging.

Figure 5.

Scout dosimetry using a small dose of resin rather than Tc-MAA. A patient with a 4.5 cm HCC. (a–c) Therapeutic ⁹⁰Y administration of 30 mCi with corresponding (a) fusion, (b) PET, and (c) CT. (d–f) Scout ⁹⁰Y dose of 15 mCi. (g–i) Tc99-MAA administration of 2 mCi. CT, computed tomography; HCC, hepatocellular carcinoma; PET, positron emission tomography; Tc-MAA, ^99mTechnetium-macroaggregated albumin.