Radioembolization (TARE)

Mapping (Part 1):

• Obtain common femoral or radial access. Some recommend alternating femoral access for mapping vs treatment, e.g., left femoral for mapping and right femoral for treatment so access is closer to table for delivery.

• Select arteries to evaluate with base 4-5 Fr catheter pending preprocedure imaging. Often the common hepatic artery +/- other arteries for variant anatomy or to assess for parasitized tumor supply.

  • Common catheters include the C2 and Simmons 1. Some use an RH catheter for women with smaller aorta and more acute origin of the celiac. Mikaelson often works well for the left gastric and right inferior phrenic.

  • Up to 50% of patients will have variant hepatic arterial anatomy. Common examples include replaces or accessory right or left hepatic arteries arising from the SMA or left gastric, respectively.

  • Common parasitized vascular supply to consider. More common after previous treatment.

    • Right superior/dome lesions - right inferior phrenic

    • Right inferior tumors - suprarenal/capsular branches of the right renal artery, omental, and supraduodenal arteries

    • Left tumors - gastric arteries and internal mammary

• Lots of variation in approaches. The important thing is to be systematic to map out the target tumor supply, volume(s) to be treated for dosimetry, and potential collaterals/variants to avoid non-target embolization.

  • Some start with an abdominal aortogram if concerned about parasitized vascular supply.

  • Most obtain a run from the common hepatic artery in AP and 30* RAO to lay out the hepatic vascular anatomy to use as a roadmap (e.g. 3 mL for 12 mL or 15 mL). Many will also do a cone beam CT.

  • Use a microcatheter and wire (e.g. ProGreat and fathom) to further select individual branches to further map out the tumor supply and determine a site for delivery that will fully cover the target tumor(s) while minimizing the dose to normal parenchyma. Often people will perform both runs and cone beam CTs for target branches.

• (Optional) Embolization, often using coils, of non-dominant branches feeding the tumor to redirect supply from the vessel(s) planned for delivery. Can also embolize collaterals/variants arteries supplying extrahepatic structures downstream of the planned delivery site to avoid non-target embolization.

  • Common collaterals/variants to avoid embolizing. Look for unique flow dynamics to identify, e.g., persisting on delay due to different capillary filling pressures.

    • From the right hepatic arteries - cystic artery, supraduodenal arteries

    • From the left hepatic arteries - accessory gastric or esophageal, left phrenic, falciform artery

• (Optional) Chemoembolization for smaller non-dominant tumors.

• Deliver Tc99m-macroaggregated albumin (MAA), ideally from the location of planned delivery.

• Some institutions do same day mapping and delivery and send the patient to nuclear medicine with microcatheter still in place. Most remove catheters/sheath, get hemostasis, send to nuc med, and have the patient come back a different day to order dose accordingly.

Dosimetry:

• Glass microspheres (Therasphere) dosing was originally based on treatment volume (MIRD model), but does not account for actually tumor volume. Resin microspheres (SIRspheres) dosing was originally based on body surface area and tumor to liver volume ratio (BSA model), which is vulnerable to mismatch between patient size and actual liver volume (e.g. obesity or hepatomegaly)

  • Personalize dosimetry or a partition model are likely superior to calculate tumor, non-tumor treated, and non-tumor non-treated volumes and doses.

• Generally three approaches with different dosing:

  • Traditional lobar dosing for widespread multi-focal disease

  • Radiation segmentectomy with ablative dose for early stage disease as definitive treatment or downstage for transplant

  • Subablative lobar or larger area treatment with “boost” or more ablative dose to smaller area for advanced stage disease

• Limits: 

  • Max of 2 segments per treatment for radiation segmentectomy. Try to leave at least 30% of liver untreated.

  • 20% lung shunt

  • 30 Gy per session or 50 Gy for life (TheraSpheres), 30 Gy (SIRSpheres)

• Risk of Radiation Induced Liver Injury (RILI)

  • >40-100 Gy to normal liver (max tolerable dose for cirrhotic v. non-cirrhotic liver = 70 v. 80 Gy).

  • Certain chemo potentiates Y90 effects [gemcitabine and capecitabine (Xeloda)] or makes the liver more sensitive to toxicity by being hepatotoxic themselves (oxaliplatin, paclitaxel)

• TheraSpheres (glass): less embolic and hotter, approved for HCC, dose calculator

  • Ordering: specific dose calibrated on Sunday 12:00 ET, second week dose would have more particles for big area

  • Target dosing: >400 Gy for segmentectomy, >205 Gy to targeted tumor and 140-150 Gy to surrounding tissue for lobar, >205 Gy to targeted tumor and 120 Gy to surrounding tissue for whole liver

• SIRSpheres (resin): more embolic and less hot, used for mets more than HCC

  • Ordering:  Same amount delivered regardless and pipetted out

  • Target dosing: >250 Gy for segmentectomy, >170 Gy to targeted tumor and 100-120 Gy to surrounding tissue for lobar, >100-120 Gy for whole liver

Options For High Shunt Fraction:

• Ward et al estimates 89% can still be treated using combination of the techniques below.

• Bland/TACE to reduce via Embospheres 500-700 um NOT to stasis as it may prevent future TARE followed by TARE in 10-14 days

• Low-dose or segmental TARE.

• Balloon occlusion of treatment side and middle hepatic veins prior to TARE until 1-5 min after, e.g.  5.5 Fr Fogarty via two 6 Fr IJ sheaths with aspiration prior to deflation.

• Embolization of competing outflow veins in the setting of hepatofugal portal flow.

• Systemic chemo for 8-12 wks followed by repeat mapping.

Delivery (Part 2):

• Obtain femoral or radial access. Some recommend alternating femoral access for mapping vs treatment, e.g., left femoral for mapping and right femoral for treatment.

• 5 Fr catheter to access celiac and SMA (often Sos or C2) -> DSA runs of celiac and SMA +/- DynaCT

• Advance microcatheter to selective target hepatic artery, e.g., ProGreat and Fathom wire 

• Hook up Y90 and infuse. With Resin beads or smaller targets may need to assess intermittently for stasis. If sluggish flow, pause 1-2 min and reassess. 

• Treatment of cystic artery likely safe - reports of some pain during injection and after, 50% had GB wall  thickening on 1 month follow up CT

• Flush microcatheter with 20 mL syringes of D5W prior to removal.

• Discard catheter and repeat if performing other treatments

• Remove sheath and obtain hemostasis