Lung Dose Measured on Postradioembolization 90Y PET/CT and Incidence of Radiation Pneumonitis

Long-Term Multifocal Pulmonary Fibrosis Associated with Y-90 Embolization: A Case Report and Literature Review

Radioembolization with Yttrium-90 (Y-90) beads is used to shrink liver tumors and reduce the tumor burden. However, a side effect of this treatment can be the shunting of Y-90 beads to the pulmonary circulation, leading to short-term radiation pneumonitis. While the short-term effects of hepatopulmonary shunting are well-defined, long-term complications have not been explored in the literature. We discuss the finding of multifocal interstitial pulmonary fibrosis in a patient treated with Y-90 for hepatocellular carcinoma. The reticular opacities were identified on chest CT scans seven months after the procedure and continued to consolidate up to 75 months post-radioembolization. Pathology confirmed multifocal fibrosis associated with Y-90 beads. This happened despite a low LSF and in the absence of clinical evidence of post-treatment radiation pneumonitis or chronic interstitial lung disease. This case report identifies radiation fibrosis as a differential diagnostic consideration when working up post-radioembolization patients with unexplained reticular opacities on lung imaging.

Evaluation of long axial field-of-view (LAFOV) PET/CT for post-treatment dosimetry in Yttrium-90 radioembolization of liver tumors: a comparative study with conventional SPECT imaging

PURPOSE

Long axial field-of-view (LAFOV) positron emission tomography/computed tomography (PET/CT) scanners enable high sensitivity and wide anatomical coverage. Therefore, they seem ideal to perform post-selective internal radiation therapy (SIRT) 90Y scans, which are needed, to confirm that the dose is delivered to the tumors and that healthy organs are spared. However, it is unclear to what extent the use of LAFOV PET is feasible and which dosimetry approaches results in accurate measurements.

METHODS

In this retrospective analysis, a total number of 32 patients was included (median age 71, IQR 14), which had hepatocellular carcinoma, cholangiocarcinoma, or liver metastases. All patients underwent SIRT, and the post-therapy scan was acquired on a single photon emission computed tomography/computed tomography (SPECT/CT) and a LAFOV Biograph Quadra PET/CT with a 20-minute acquisition time. Post-treatment dosimetry, regarding the tumor, whole-liver and lung (LMD) absorbed dose was done using an organ-wise (Simplicit90Y) and a voxel-wise approach (HERMIA Dosimetry) which used a semi-Monte Carlo algorithm. The lung shunt fraction (LSF) was also measured using the voxel-wise approach and compared to the planned.

RESULTS

The planning, post-treatment SPECT and PET (SPECTpre, SPECTpost, PETpost) median tumor doses based on the organ-wise dosimetry were 276.0 Gy (200.0-330.0 Gy), 232.0 Gy (158.5-303.5 Gy) and 267.5 Gy (182.5-370.8 Gy). In contrast, the median voxel-wise PETpost dose was significantly smaller than the planned SPECTpre (152.5 Gy (94.8-223.8 Gy); p < 0.00001). Moreover, the median tumor absorbed dose at 90% (D90) of the tumor volume was significantly higher in SPECTpost compared with PETpost (123.5 Gy; 81.5-180.0 vs. 30.5 Gy; 11.3-106.3; p < 0.00001). The PETpost measured LSF was significantly lower compared to the planned SPECTpre (0.89%; 0.4-1.3% vs. 2.3%; 1.5-3.6%; p < 0.0001). Similarly, the measured PETpost median LMD was considerably lower to the planned SPECTpre (1.2 Gy; 0.6-2.3 vs. 2.5 Gy; 1.4-4.7; p < 0.0001).

CONCLUSION

LAFOV PET enabled the direct measurement of post therapy lung dose and tumor doses that correlated well with the planned treatment doses. However, current voxel-wise-based tumor dosimetry seems to be inaccurate for LAFOV PET. In addition, dose volume histogram-based metrics also significantly underestimate the delivered dose. Therefore, improved dosimetry tools are needed for reliable voxel-wise 90Y dosimetry to leverage the sensitivity and spatial resolution of LAFOV PET scanners.

Radiation Pneumonitis after Yttrium-90 Radioembolization: A Systematic Review

PURPOSE

To evaluate the available evidence of lung dosimetry and radiation pneumonitis (RP).

MATERIALS AND METHODS

The guideline regarding the maximum tolerated lung dose for yttrium-90 (90Y) radioembolization is an expert opinion (Level 5 evidence) based on a case series of 5 patients and recommends keeping the absorbed radiation dose to the lungs below 30 Gy per treatment and 50 Gy in a lifetime to prevent RP. The current understanding of the risks of RP is minimal despite its debilitating nature and high mortality rate. A systematic literature review was conducted in PubMed, Embase, Cochrane database, and Google Scholar for reported cases of RP. A database of 48 RP cases was compiled and analyzed.

RESULTS

Thirty patients were treated with resin and 16 patients with glass 90Y microspheres. The treatment device was not reported in 2 cases. RP developed a median of 3 months after radioembolization. The mortality rate was 40%. The hepatopulmonary shunt was not significantly different between the glass and the resin groups (21.2% [SD ± 14%] vs 15.6% [SD ± 7.5%]; P = .24). The radiation dose to the lungs was significantly higher in patients treated with glass compared with those with resin 90Y microspheres (41.4 Gy [SD ± 18.4] vs 21.5 Gy [SD ± 9.9]; P = .003).

CONCLUSIONS

The dose toxicity threshold for resin microspheres is lower than that of glass microspheres. The established 30-Gy dose limit may not be uniformly applicable in all cases and for both devices. The maximum tolerable lung doses should be reevaluated, and the shortcomings of the hepatopulmonary shunt calculation need to be corrected.

Addressing lung truncation in 99mTc-MAA SPECT/CT for 90Y microsphere radioembolization treatment planning

BACKGROUND

Prior studies have established that macroaggregated albumin (MAA)-SPECT/CT offers more robust lung shunt fraction (LSF) and lung mean absorbed dose (LMD) estimates in 90Y radioembolization in comparison to planar imaging. However, incomplete SPECT/CT coverage of the lungs is common due to clinical workflows, complicating its potential use for LSF and LMD calculations. In this work, lung truncation in MAA-SPECT/CT was addressed via correction strategies to improve 90Y treatment planning.

METHODS

Lung truncation was simulated in 56 cases with adequate (> 90%, mean: 98%) lung coverage in MAA-SPECT/CT by removing slices in ~ 5 mm increments from the lung apices to the diaphragm. A wide range of lung coverages from 100% to < 1% in ~ 2% increments were created. LSF and LMD were calculated with four methods. (1) 2D planar imaging standard (not truncated), truncated lung SPECT/CT data was: (2) used with no corrections (SPECTTrunc), (3) uniformly extrapolated to full lung coverage (SPECTUniform), (4) fit with an empirical model to predict lung counts at full lung coverage (SPECTFit). To determine counts for LSF, full lung volumes, those modified at the lung/liver boundary (Lungs 2-cm), and those isolated to the left lung (Left Lung) were used. The correction methods were then applied to 31 independent cases without full lung coverage (< 90%, mean: 74%). The variations in LSF and LMD estimates from each correction method were analyzed.

RESULTS

Averaged across simulated lung coverages from 40 to 80%, percent errors relative to non-truncated data for SPECTTrunc were (mean ± σ) - 22% ± 15% for LSF and 34% ± 29% for LMD. SPECTUniform had similar errors with 29% ± 26% for both LSF and LMD. SPECTFit yielded the most accurate and precise estimates for LSF and LMD, with errors of 11% ± 20% for both. The Left Lung approach equalized LMD errors in all three correction methods, with percent errors of 3% ± 17% (SPECTTrunc), 2% ± 17% (SPECTUniform), and 4% ± 13% (SPECTFit). In the 31 cases without ground truth LSF or LMD, Left Lung produced highly comparable LMD estimates, with a mean (max) coefficient of variation across the three correction methods of 4% (20%).

CONCLUSION

LSF and LMD can be estimated for 90Y radioembolization using truncated lung coverage data in MAA-SPECT/CT. Empirical models to predict lung counts at full lung coverage produced LSF and LMD estimates with minimal bias and uncertainty. With lung/liver boundary adjustments, all SPECT/CT methods assessed in this work yielded LMD estimates comparable to ground truth, even down to 50% lung coverage.

A 78-Year-Old Man With Shortness of Breath After Radioembolization of the Liver

CASE PRESENTATION

A 78-year-old man with a history of GI stromal tumor (GIST) in the stomach with metastasis to the liver presented with progressive shortness of breath, dry cough, and subjective fever that started 1 week after radioembolization of liver metastatic lesions. His initial diagnosis of GIST was 10 years before, for which he underwent surgical resection; however, more recently he was noted to have hepatic lesions biopsy-proven to be metastatic GIST lesions. He stated that he did not have any respiratory symptoms before the radioembolization procedure and denied having a history of pulmonary disease. His medical history was otherwise notable for coronary artery disease post coronary artery bypass graft in 2002, heart failure with reduced ejection fraction, and atrioventricular block after pacemaker placement. After the diagnosis of liver metastasis, he began treatment with imatinib 6 months earlier and consequently received radioembolization with yttrium-90 (Y-90) microspheres.

90Y post-radioembolization clinical assessment with whole-body Biograph Vision Quadra PET/CT: image quality, tumor, liver and lung dosimetry

PURPOSE

Evaluation of 90Y liver radioembolization post-treatment clinical data using a whole-body Biograph Vision Quadra PET/CT to investigate the potential of protocol optimization in terms of scan time and dosimetry.

METHODS

17 patients with hepatocellular carcinoma with median (IQR) injected activity 2393 (1348-3298) MBq were included. Pre-treatment dosimetry plan was based on 99mTc-MAA SPECT/CT with Simplicit90Y™ and post-treatment validation with Quadra using Simplicit90Y™ and HERMIA independently. Regarding the image analysis, mean and peak SNR, the coefficient of variation (COV) and lesion-to-background ratio (LBR) were evaluated. For the post-treatment dosimetry validation, the mean tumor, whole liver and lung absorbed dose evaluation was performed using Simplicit90Y and HERMES. Images were reconstructed with 20-, 15-, 10-, 5- and 1- min sinograms with 2, 4, 6 and 8 iterations. Wilcoxon signed rank test was used to show statistical significance (p < 0.05).

RESULTS

There was no difference of statistical significance between 20- and 5- min reconstructed times for the peak SNR, COV and LBR. In addition, there was no difference of statistical significance between 20- and 1- min reconstructed times for all dosimetry metrics. Lung dosimetry showed consistently lower values than the expected. Tumor absorbed dose based on Simplicit90Y™ was similar to the expected while HERMES consistently underestimated significantly the measured tumor absorbed dose. Finally, there was no difference of statistical significance between expected and measured tumor, whole liver and lung dose for all reconstruction times.

CONCLUSION

In this study we evaluated, in terms of image quality and dosimetry, whole-body PET clinical images of patients after having been treated with 90Y microspheres radioembolization for liver cancer. Compared to the 20-min standard scan, the simulated 5-min reconstructed images provided equal image peak SNR and noise behavior, while performing also similarly for post-treatment dosimetry of tumor, whole liver and lung absorbed doses.

Clinical predictors of severe radiation pneumonitis in patients undergoing thoracic radiotherapy for lung cancer

Background

Severe radiation pneumonitis (RP), one of adverse events in patients with lung cancer receiving thoracic radiotherapy, is more likely to lead to more mortality and poor quality of life, which could be predicted by clinical information and treatment scheme. In this study, we aimed to explore the clinical predict model for severe RP.

Methods

We collected information on lung cancer patients who received radiotherapy from August 2020 to August 2022. Clinical features were obtained from 690 patients, including baseline and treatment data as well as radiation dose measurement parameters, including lung volume exceeding 5 Gy (V5), lung volume exceeding 20 Gy (V20), lung volume exceeding 30 Gy (V30), mean lung dose (MLD), etc. Among them, 621 patients were in the training cohort, and 69 patients were in the test cohort. Three models were built using different screening methods, including multivariate logistics regression (MLR), backward stepwise regression (BSR), and random forest regression (RFR), to evaluate their predictive power. Overoptimism in the training cohorts was evaluated by four validation methods, including hold-out, 10-fold, leave-one-out, and bootstrap methods, and test cohort was used to evaluate the predictive performance of the model. Model calibration, decision curve analysis (DCA), and evaluation of the nomograms for the three models were completed.

Results

Severe RP was up to 9.4%. The results of multivariate analysis of logistics regression in all patients showed that patients with subclinical (untreated and asymptomatic) interstitial lung disease (ILD) could increase the risk of severe RP, and patients with a better lung diffusion function and received standardized steroids treatment could decrease the risk of severe RP. The three models built by MLR, BSR, and RFR all had good accuracy (>0.850) and moderate κ value (>0.4), and the model 2 built by BSR had the highest area under the receiver operating characteristic (ROC) curve (AUC) in three models, which was 0.958 [95% confidence interval (CI): 0.932-0.985]. The calibration curve showed good agreement between the predicted and actual values, and the DCA showed a positive net benefit for the model 2 which drew the nomogram. The model 2 included subclinical ILD, diffusing capacity of the lung for carbon monoxide (DLCO), ipsilateral lung V20, and standardized steroid treatment, which could affect the incidence of severe RP.

Conclusions

Subclinical ILD, DLCO, ipsilateral lung V20, and with or not standardized steroid treatment could affect the incidence of severe RP. Strict lung dose limitation and standardized steroid treatment could contribute to a decrease in severe RP.

Lung Mean Dose Prediction in Transarterial Radioembolization (TARE): Superiority of [166Ho]-Scout Over [99mTc]MAA in a Prospective Cohort Study

PURPOSE

Radiation pneumonitis is a serious complication of radioembolization. In holmium-166 ([166Ho]) radioembolization, the lung mean dose (LMD) can be estimated (eLMD) using a scout dose with either technetium-99 m-macroaggregated albumin ([99mTc]MAA) or [166Ho]-microspheres. The accuracy of eLMD based on [99mTc]MAA (eLMDMAA) was compared to eLMD based on [166Ho]-scout dose (eLMDHo-scout) in two prospective clinical studies.

MATERIALS AND METHODS

Patients were included if they received both scout doses ([99mTc]MAA and [166Ho]-scout), had a posttreatment [166Ho]-SPECT/CT (gold standard) and were scanned on the same hybrid SPECT/CT system. The correlation between eLMDMAA/eLMDHo-scout and LMDHo-treatment was assessed by Spearman's rank correlation coefficient (r). Wilcoxon signed rank test was used to analyze paired data.

RESULTS

Thirty-seven patients with unresectable liver metastases were included. During follow-up, none developed symptoms of radiation pneumonitis. Median eLMDMAA (1.53 Gy, range 0.09-21.33 Gy) was significantly higher than median LMDHo-treatment (0.00 Gy, range 0.00-1.20 Gy; p < 0.01). Median eLMDHo-scout (median 0.00 Gy, range 0.00-1.21 Gy) was not significantly different compared to LMDHo-treatment (p > 0.05). In all cases, eLMDMAA was higher than LMDHo-treatment (p < 0.01). While a significant correlation was found between eLMDHo-scout and LMDHo-treatment (r = 0.43, p < 0.01), there was no correlation between eLMDMAA and LMDHo-treatment (r = 0.02, p = 0.90).

CONCLUSION

[166Ho]-scout dose is superior in predicting LMD over [99mTc]MAA, in [166Ho]-radioembolization. Consequently, [166Ho]-scout may limit unnecessary patient exclusions and avoid unnecessary therapeutic activity reductions in patients eligible for radioembolization.

TRAIL REGISTRATION

NCT01031784, registered December 2009. NCT01612325, registered June 2012.

PET/CT and SPECT/CT imaging of 90Y hepatic radioembolization at therapeutic and diagnostic activity levels: Anthropomorphic phantom study

PURPOSE

Prior to 90Y radioembolization procedure, a pretherapy simulation using 99mTc-MAA is performed. Alternatively, a small dosage of 90Y microspheres could be used. We aimed to assess the accuracy of lung shunt fraction (LSF) estimation in both high activity 90Y posttreatment and pretreatment scans with isotope activity of ~100 MBq, using different imaging techniques. Additionally, we assessed the feasibility of visualising hot and cold hepatic tumours in PET/CT and Bremsstrahlung SPECT/CT images.

MATERIALS AND METHODS

Anthropomorphic phantom including liver (with two spherical tumours) and lung inserts was filled with 90Y chloride to simulate an LSF of 9.8%. The total initial activity in the liver was 1451 MBq, including 19.4 MBq in the hot sphere. Nine measurement sessions including PET/CT, SPECT/CT, and planar images were acquired at activities in the whole phantom ranging from 1618 MBq down to 43 MBq. The visibility of the tumours was appraised based on independent observers' scores. Quantitatively, contrast-to-noise ratio (CNR) was calculated for both spheres in all images.

RESULTS

LSF estimation. For high activity in the phantom, PET reconstructions slightly underestimated the LSF; absolute difference was <1.5pp (percent point). For activity <100 MBq, the LSF was overestimated. Both SPECT and planar scintigraphy overestimated the LSF for all activities. Lesion visibility. For SPECT/CT, the cold tumour proved too small to be discernible (CNR <0.5) regardless of the 90Y activity in the liver, while hot sphere was visible for activity >200 MBq (CNR>4). For PET/CT, the cold tumour was only visible with the highest 90Y activity (CNR>4), whereas the hot one was seen for activity >100 MBq (CNR>5).

CONCLUSIONS

PET/CT may accurately estimate the LSF in a 90Y posttreatment procedure. However, at low activities of about 100 MBq it seems to provide unreliable estimations. PET imaging provided better visualisation of both hot and cold tumours.

The Evolving Role of Radioembolization in the Treatment of Neuroendocrine Liver Metastases

At diagnosis, 21-50% of neuroendocrine tumors already have distant metastases, of which the liver is most commonly affected. Unfortunately, the presence of neuroendocrine liver metastases (NELM) is the most incriminating factor for survival. At NELM diagnosis, 60-70% of patients suffer from bilobar multifocal disease, making them ineligible for surgical resection. With limited systemic options, a clinical need for liver-directed treatments exists. Trans-arterial (bland) embolization, chemoembolization and radioembolization have been increasingly used in the treatment of NELM. In recent years, radioembolization (also known as selective internal radiation therapy) has gained attention due to promising tumor reductive results, limited toxicities and increasing scientific evidence. This review provides basic insights into radioembolization as a technique, a summary of available literature on radioembolization in NELM, and discusses caveats, challenges and new insights when considering radioembolization in NELM.