Radioembolization with Y-90 Glass Microspheres: Do We Really Need SPECT-CT to Identify Extrahepatic Shunts?

Extrahepatic perfusion and incomplete hepatic perfusion after hepatic arterial infusion pump implantation: incidence and clinical implications

INTRODUCTION

This study investigates the incidence of extrahepatic perfusion and incomplete hepatic perfusion at intraoperative methylene blue testing and on postoperative nuclear imaging in patients undergoing hepatic arterial infusion pump (HAIP) chemotherapy.

METHODS

The first 150 consecutive patients who underwent pump implantation in the Netherlands were included. All patients underwent surgical pump implantation with the catheter in the gastroduodenal artery. All patients underwent intraoperative methylene blue testing and postoperative nuclear imaging (99mTc-Macroaggregated albumin SPECT/CT) to determine perfusion via the pump.

RESULTS

Patients were included between January-2018 and December-2021 across eight centers. During methylene blue testing, 29.3% had extrahepatic perfusion, all successfully managed intraoperatively. On nuclear imaging, no clinically relevant extrahepatic perfusion was detected (0%, 95%CI: 0.0-2.5%). During methylene blue testing, 2.0% had unresolved incomplete hepatic perfusion. On postoperative nuclear imaging, 8.1% had incomplete hepatic perfusion, leading to embolization in only 1.3%.

CONCLUSION

Methylene blue testing during pump placement for intra-arterial chemotherapy identified extrahepatic perfusion in 29.3% of patients, but could be resolved intraoperatively in all patients. Postoperative nuclear imaging found no clinically relevant extrahepatic perfusion and led to embolization in only 1.3% of patients. The role of routine nuclear imaging after HAIP implantation should be studied in a larger cohort.

Non Target Shunting of Tc-99m Macroaggregates of Albumin and Radiolabeled Yttrium-90 Microspheres into Hepatic Falciform Artery - Less Observed Arterial Variant not to be Overlooked

Identification of nontarget arteries is crucial prior to Yttrium-90 microspheres radioembolization. We present a case where an uncommon nontarget artery, the hepatic falciform artery was identified during work up for radioembolization and necessary preventive measures were taken to minimize the complications.

A Theranostic Approach in SIRT: Value of Pre-Therapy Imaging in Treatment Planning

Selective internal radiation therapy (SIRT) is one of the treatment options for liver tumors. Microspheres labelled with a therapeutic radionuclide (⁹⁰Y or ¹⁶⁶Ho) are injected into the liver artery feeding the tumor(s), usually achieving a high tumor absorbed dose and a high tumor control rate. This treatment adopts a theranostic approach with a mandatory simulation phase, using a surrogate to radioactive microspheres (^99mTc-macroaggregated albumin, MAA) or a scout dose of ¹⁶⁶Ho microspheres, imaged by SPECT/CT. This pre-therapy imaging aims to evaluate the tumor targeting and detect potential contraindications to SIRT, i.e., digestive extrahepatic uptake or excessive lung shunt. Moreover, the absorbed doses to the tumor(s) and the healthy liver can be estimated and used for planning the therapeutic activity for SIRT optimization. The aim of this review is to evaluate the accuracy of this theranostic approach using pre-therapy imaging for simulating the biodistribution of the microspheres. This review synthesizes the recent publications demonstrating the advantages and limitations of pre-therapy imaging in SIRT, particularly for activity planning.

Using an Assumed Lung Mass Inaccurately Estimates the Lung Absorbed Dose in Patients Undergoing Hepatic 90Yttrium Radioembolization Therapy

RATIONALE

Currently, the estimated absorbed radiation dose to the lung in ⁹⁰Y radioembolization therapy is calculated using an assumed 1 kg lung mass for all patients. The aim of this study was to evaluate whether using a patient-specific lung mass measurement for each patient rather than a generic, assumed 1 kg lung mass would change the estimated lung absorbed dose.

METHODS

A retrospective analysis was performed on 68 patients who had undergone ⁹⁰Y radioembolization therapy at our institution. Individualized lung volumes were measured manually on CT scans for each patient, and these volumes were used to calculate personalized lung masses. The personalized lung masses were used to recalculate the estimated lung absorbed dose from the ⁹⁰Y therapy, and this dose was compared to the estimated lung absorbed dose calculated using an assumed 1 kg lung mass.

RESULTS

Patient-specific lung masses were significantly different from the generic 1 kg when compared individually for each patient (p < 0.0001). Median individualized lung mass was 0.71 (IQR: 0.59, 1.02) kg overall and was significantly different from the generic 1 kg lung mass for female patients [0.59 (0.50, 0.68) kg, (p < 0.0001)] but not for male patients [0.99 (0.71, 1.14) kg, (p = 0.24)]. Median estimated lung absorbed dose was 4.48 (2.38, 11.71) Gy using a patient-specific lung mass and 3.45 (1.81, 6.68) Gy when assuming a 1 kg lung mass for all patients. The estimated lung absorbed dose was significantly different using a patient-specific versus generic 1 kg lung mass when comparing the doses individually for each patient (p < 0.0001). The difference in the estimated lung absorbed dose between the patient-specific and generic 1 kg lung mass method was significant for female patients as a subgroup but not for male patients.

CONCLUSIONS

The current method of assuming a 1 kg lung mass for all patients inaccurately estimates the lung absorbed dose in ⁹⁰Y radioembolization therapy. Using patient-specific lung masses resulted in estimated lung absorbed doses that were significantly different from those calculated using an assumed 1 kg lung mass for all patients. A personalized dosimetry method that includes individualized lung masses is necessary and can warrant a ⁹⁰Y dose reduction in some patients with lung masses smaller than 1 kg.

LEVEL OF EVIDENCE

Level 3, Retrospective Study.

Monte Carlo 90Y PET/CT dosimetry of unexpected focal radiation-induced lung damage after hepatic radioembolisation

Transarterial radioembolization (TARE) with ⁹⁰Y-loaded microspheres is an established therapeutic option for inoperable hepatic tumors. Increasing knowledge regarding TARE hepatic dose-response and dose-toxicity correlation is available but few studies have investigated dose-toxicity correlation in extra-hepatic tissues. We investigated absorbed dose levels for the appearance of focal lung damage in a case of off-target deposition of ⁹⁰Y microspheres and compared them with the corresponding thresholds recommended to avoiding radiation induced lung injury following TARE. A 64-year-old male patient received 1.6 GBq of ⁹⁰Y-labelled glass microspheres for an inoperable left lobe hepatocellular carcinoma. A focal off-target accumulation of radiolabeled microspheres was detected in the left lung upper lobe at the post-treatment ⁹⁰Y-PET/CT, corresponding to a radiation-induced inflammatory lung lesion at the 3-months ¹⁸F-FDG PET/CT follow-up. ⁹⁰Y-PET/CT data were used as input for Monte-Carlo based absorbed dose estimations. Dose-volume-histograms were computed to characterize the heterogeneity of absorbed dose distribution. The dose level associated with the appearance of lung tissue damage was estimated as the median absorbed dose measured at the edge of the inflammatory nodule. To account for respiratory movements and possible inaccuracy of image co-registration, three different methods were evaluated to define the irradiated off-target volume. Monte Carlo-derived absorbed dose distribution showed a highly heterogeneous absorbed dose pattern at the site of incidental microsphere deposition (volume = 2.13 ml) with a maximum dose of 630 Gy. Absorbed dose levels ranging from 119 Gy to 133 Gy, were estimated at the edge of the inflammatory nodule, depending on the procedure used to define the target volume. This report describes an original Monte Carlo based patient-specific dosimetry methodology for the study of the radiation-induced damage in a focal lung lesion after TARE. In our patient, radiation-induced focal lung damage occurred at significantly higher absorbed doses than those considered for single administration or cumulative lung dose delivered during TARE.

Analysis of failed therapy evaluations in radioembolization of primary and secondary liver cancers

Purpose

To analyze patients’ characteristics and reasons for not performing planned transarterial radioembolization (TARE) in liver cancer after ^99mTc-labeled macroaggregated albumin (^99mTc-MAA) evaluation.

Methods

In this retrospective single-center cohort, all patients undergoing ^99mTc-MAA evaluation prior to planned TARE for primary or secondary liver cancer between 2009 and 2018 were analyzed. Patients were assigned to either “TARE” or “no TARE” group. Patients’ characteristics, arising reasons for not performing the planned TARE treatment as well as predictive factors for occurrence of these causes were analyzed.

Results

436 patients [male = 248, female = 188, median age 62 (23–88) years] with ^99mTc-MAA evaluation prior to planned TARE of primary or secondary liver cancer were included in this study. 148 patients (33.9%) did not receive planned TARE. Patients with a hepatic tumor burden > 50%, no liver cirrhosis, no previous therapies and a higher bilirubin were significantly more frequent in “no TARE” compared to “TARE” group. Main reasons for not performing TARE were extrahepatic tracer accumulation (n = 70, 40.5%), non-target accumulation of ^99mTc-MAA (n = 27, 15.6%) or a hepatopulmonary shunt fraction of more than 20% (n = 23, 13.3%). Independent preprocedural parameters for not performing planned TARE were elevated bilirubin (p = 0.021) and creatinine (p = 0.018) and lower MELD score (p = 0.031).

Conclusion

A substantial number of patients are precluded from TARE following ^99mTc-MAA evaluation, which is, therefore, implicitly needed to determine contraindications to TARE and should not be refrained from in pretreatment process. However, a preceding careful patient selection is needed especially in patients with high hepatic tumor burden and alteration in lab parameters.

Foreign body granuloma reaction following SIRT mimicking peritoneal metastases: a word of caution

Intrahepatic cholangiocarcinoma (iCCA) is the second most common primary liver malignancy with poor survival rates. Surgical resection is the only curative treatment option, yet only a small portion of cases are resectable. In unresectable situations, suggested therapy consists of a systemic chemotherapy regimen with cisplatinum and gemcitabine. Selective internal radiation therapy (SIRT) has been proposed as an alternative treatment option and may lead to downstaging of unresectable iCCA to surgery. We present a case of a female patient diagnosed with an unresectable iCCA treated with SIRT in order to obtain downstaging. Explorative laparoscopy three months later showed multiple peritoneal lesions in the left upper quadrant, mimicking peritoneal metastases. Anatomopathological investigation showed a foreign body granuloma surrounding the SIRT resin particles. These findings have important consequences, as the presence of peritoneal metastases implies a palliative situation. Anatomopathological confirmation of any intra-abdominal lesion mimicking peritoneal metastases should be carried out.

Safety analysis of holmium-166 microsphere scout dose imaging during radioembolisation work-up: A cohort study

OBJECTIVE

Radioembolisation is generally preceded by a scout dose of technetium-99m-macroaggregated albumin to estimate extrahepatic shunting of activity. Holmium-166 microspheres can be used as a scout dose (±250 MBq) and as a therapeutic dose. The general toxicity of a holmium-166 scout dose (166Ho-SD) and safety concerns of an accidental extrahepatic deposition of 166Ho-SD were investigated.

METHODS

All patients who received a 166Ho-SD in our institute were reviewed for general toxicity and extrahepatic depositions. The absorbed dose in extrahepatic tissue was calculated on SPECT/CT and correlated to clinical toxicities.

RESULTS

In total, 82 patients were included. No relevant clinical toxicity occurred. Six patients had an extrahepatic deposition of 166Ho-SD (median administered activity 270 MBq). The extrahepatic depositions (median activity 3.7 MBq) were located in the duodenum (3x), gastric fundus, falciform ligament and the lesser curvature of the stomach, and were deposited in a median volume of 15.3 ml, which resulted in an estimated median absorbed dose of 3.6 Gy (range 0.3-13.8 Gy). No adverse events related to the extrahepatic deposition of the 166Ho-SD occurred after a median follow-up of 4 months (range 1-12 months).

CONCLUSION

These results support the safety of 250 MBq 166Ho-SD in a clinical setting.

KEY POINTS

• A holmium-166 scout dose is safe in a clinical setting. • Holmium-166 scout dose is a safe alternative for 99m Tc-MAA for radioembolisation work-up. • Holmium-166 scout dose potentially has several benefits over 99m Tc-MAA for radioembolisation work-up.