Extravasation of a Therapeutic Dose of 131I-Metaiodobenzylguanidine: Prevention, Dosimetry, and Mitigation

Dose Estimation for Extravasation of 177Lu, 99mTc, and 18F

ABSTRACT

Extravasation is the situation in which a nuclear medicine injection deposits some fraction of its radioactivity into the soft tissue rather than the bloodstream and may result in a large local radiation dose to tissue. An understanding of localized radiation dose from such unexpected events can be an important aspect of clinical radiation protection. The aim of this study was to estimate and assess absorbed radiation dose to localized soft tissue for hypothetical scenarios of radiopharmaceutical extravasation. Specifically, the goal was to understand whether a radiopharmaceutical extravasation could exceed the US Nuclear Regulatory Commission's medical event reporting limit of 0.5 Sv dose equivalent to tissue or levels at which tissue damage would be anticipated (1.0 Sv dose equivalent). We used the GATE Monte Carlo simulation software to calculate self-dose to spherical volumes containing uniformly distributed amounts of common radiopharmaceutical isotopes. Simulated volumes, radioactivity levels, and effective half-lives represented real-world nuclear medicine procedures. Chosen scenarios consisted of 50 mCi and 100 mCi 177Lu within 20 cm3 and 40 cm3 tissue volumes and a 60 min biological clearance half-time (59.6 min effective half-life), 6 mCi and 12 mCi 99mTc within 1 cm3 and 5 cm3 tissue volumes and a 120 min biological clearance half-time (90 min effective half-life), and 3 mCi and 6 mCi 18F within 1 cm3 and 5 cm3 tissue volumes with a 30 min biological clearance half-time (23.6 min effective half-life). We calculated absorbed doses to be between 5.5 Gy and 23.5 Gy for 177Lu, between 0.9 Gy and 12.4 Gy for 99mTc, and between 1.5 Gy and 16.2 Gy for 18F. Radiopharmaceutical extravasations can result in tissue doses that surpass both medical event reporting limits and levels at which deterministic effects are expected. Radiation safety programs should include identification, mitigation, dosimetry, and documentation of significant extravasation events.

Practical Tools for Patient-specific Characterization and Dosimetry of Radiopharmaceutical Extravasation

ABSTRACT

Extravasation during radiopharmaceutical injection may occur with a frequency of more than 10%. In these cases, radioactivity remains within tissue and deposits unintended radiation dose. Characterization of extravasations is a necessary step in accurate dosimetry, but a lack of free and publicly available tools hampers routine standardized analysis. Our objective was to improve existing extravasation characterization and dosimetry methods and to create and validate tools to facilitate standardized practical dosimetric analysis in clinical settings. Using Monte Carlo simulations, we calculated dosimetric values for sixteen nuclear medicine isotopes: 11 C, 64 Cu, 18 F, 67 Ga, 68 Ga, 123 I, 131 I, 111 In, 177 Lu, 13 N, 15 O, 82 Rb, 153 Sm, 89 Sr, 99m Tc, and 90 Y. We validated our simulation results against five logical alternative dose assessment methods. We then created three new characterization tools: a worksheet, a spreadsheet, and a web application. We assessed each tool by recalculating extravasation dosimetry results found in the literature and used each of the tools for patient cases to show clinical practicality. Average variation between our simulation results and alternative methods was 3.1%. Recalculation of published dosimetry results indicated an average error of 7.9%. Time required to use each characterization tool ranged from 1 to 5 min, and agreement between the three tools was favorable. We improved upon existing methods by creating new tools for characterization and dosimetry of radiopharmaceutical extravasation. These free and publicly available tools will enable standardized routine clinical analysis and benefit patient care, clinical follow-up, documentation, and event reporting.

Lutetium-177 Radiopharmeceutical Therapy Extravasation Lessons Learned

Lutetium-177 ( 177 Lu) dotatate has been offered at Fox Chase Cancer Center since 2017 as part of a clinical trial and then in 2018 as a commercially available cancer therapy, and we thought we were prepared for most 177 Lu issues by the fall of 2020. A single phone call identified that the Radiation Safety Department had not been prepared to address extravasations. Fortunately for the patient and Radiation Safety, the 177 Lu therapies are administered by an infusion nurse and Fox Chase Cancer Center has a robust infusion center. The expertise of our infusion center team helped to quickly identify specific mitigation efforts to employ. A team of radiation safety and diagnostic medical physicists worked together to estimate a tissue dose. Research was also started with the aim of identifying therapeutic 177 Lu extravasations as early as possible. The lessons we learned and plans for future early identification of 177 Lu dotatate extravasations are the basis of this paper.

177Lu-DOTA-0-Tyr3-octreotate infusion modeling for real-time detection and characterization of extravasation during PRRT

PURPOSE

Given the recent and rapid development of peptide receptor radionuclide therapy (PRRT), increasing emphasis should be placed on the early identification and quantification of therapeutic radiopharmaceutical (thRPM) extravasation during intravenous administration. Herein, we provide an analytical model of 177Lu-DOTA0-Tyr3-octreotate (Lutathera®) infusion for real-time detection and characterization of thRPM extravasation.

METHODS

For 33 Lutathera®-based PRRT procedures using the gravity infusion method, equivalent dose rates (EDRs) were monitored at the patient's arm. Models of flow dynamics for nonextravasated and extravasated infusions were elaborated and compared to experimental data through an equivalent dose rate calibration. Nonextravasated infusion was modeled by assuming constant volume dilution of 177Lu activity concentration in the vial and Poiseuille-like laminar flow through the tubing and patient vein. Extravasated infusions were modeled according to their onset times by considering elliptically shaped extravasation region with different aspect ratios.

RESULTS

Over the 33 procedures, the peak of the median EDR was reached 14 min after the start of the infusion with a value of 450 µSv h-1. On the basis of experimental measurements, 1 mSv h-1 was considered the empirical threshold for Lutathera® extravasation requiring cessation of the infusion and start again with a new route of injection. According to our model, the concentration of extravascular activity was directly related to the time of extravasation onset and its duration, a finding inherent in the gravity infusion method. This result should be considered when planning therapeutic strategy in the case of RPM extravasation because the local absorbed dose for β-emitters is closely linked to activity concentration. For selected EDR values, charts of extravasated activity, volume, and activity concentration were computed for extravasation characterization.

CONCLUSION

We proposed an analytical model of Lutathera® infusion and extravasation (gravity method) based on EDR monitoring. This approach could be useful for the early detection of thRPM extravasation and for the real-time assessment of activity concentration and volume accumulation in the extravascular medium.

Radiation Safety and Accidental Radiation Exposures in Nuclear Medicine

Medical radiation accidents and unintended events may lead to accidental or unintended medical exposure of patients and exposure of staff or the public. Most unintended exposures in nuclear medicine will lead to a small increase in risk; nevertheless, these require investigation and a clinical and dosimetric assessment. Nuclear medicine staff are exposed to radiation emitted directly by radiopharmaceuticals and by patients after administration of radiopharmaceuticals. This is particularly relevant in PET, due to the penetrating 511 keV γ-rays. Dose constraints should be set for planning the exposure of individuals. Staff body doses of 1-25 µSv/GBq are reported for PET imaging, the largest component being from the injection. The preparation and administration of radiopharmaceuticals can lead to high doses to the hands, challenging dose limits for radionuclides such as ⁹⁰Y and even ¹⁸F. The risks of contamination can be minimized by basic precautions, such as carrying out manipulations in purpose-built facilities, wearing protective clothing, especially gloves, and removing contaminated gloves or any skin contamination as quickly as possible. Airborne contamination is a potential problem when handling radioisotopes of iodine or administering radioaerosols. Manipulating radiopharmaceuticals in laminar air flow cabinets, and appropriate premises ventilation are necessary to improve safety levels. Ensuring patient safety and minimizing the risk of incidents require efficient overall quality management. Critical aspects include: the booking process, particularly if qualified medical supervision is not present; administration of radiopharmaceuticals to patients, with the risk of misadministration or extravasation; management of patients' data and images by information technology systems, considering the possibility of misalignment between patient personal data and clinical information. Prevention of possible mistakes in patient identification or in the management of patients with similar names requires particular attention. Appropriate management of pregnant or breast-feeding patients is another important aspect of radiation safety. In radiopharmacy activities, strict quality assurance should be implemented at all operational levels, in addition to adherence to national and international regulations and guidelines. This includes not only administrative aspects, like checking the request/prescription, patient's data and the details of the requested procedure, but also quantitative tests according to national/international pharmacopoeias, and measuring the dispensed activity with a calibrated activity meter prior to administration. In therapy with radionuclides, skin tissue reactions can occur following extravasation, which can result in localized doses of tens of Grays. Other relevant incidents include confusion of products for patients administered at the same time or malfunction of administration devices. Furthermore, errors in internal radiation dosimetry calculations for treatment planning may lead to under or over-treatment. According to literature, proper instructions are fundamental to keep effective dose to caregivers and family members after patient discharge below the Dose constraints. The IAEA Basic Safety Standards require measures to minimize the likelihood of any unintended or accidental medical exposures and reporting any radiation incident. The relative complexity of nuclear medicine practice presents many possibilities for errors. It is therefore important that all activities are performed according to well established procedures, and that all actions are supported by regular quality assurance/QC procedures.

The Scientific and Clinical Case for Reviewing Diagnostic Radiopharmaceutical Extravasation Long-Standing Assumptions

Background: The patient benefit from a diagnostic nuclear medicine procedure far outweighs the associated radiation risk. This benefit/risk ratio assumes a properly administered radiopharmaceutical. However, a significant diagnostic radiopharmaceutical extravasation can confound the procedure in many ways. We identified three current extravasation hypotheses espoused by medical societies, advisory committees, and hundreds of individual members of the nuclear medicine community: diagnostic extravasations do not cause harm, do not result in high absorbed dose to tissue, and require complex dosimetry methods that are not readily available in nuclear medicine centers. We tested these hypotheses against a framework of current knowledge, recent developments, and original research. We conducted a literature review, searched regulatory databases, examined five clinical cases of extravasated patients, and performed dosimetry on those extravasations to test these globally accepted hypotheses. Results: A literature review found 58 peer-reviewed documents suggesting patient harm. Adverse event/vigilance report database reviews for extravasations were conducted and revealed 38 adverse events which listed diagnostic radiopharmaceutical extravasation as a factor, despite a regulatory exemption for required reporting. In our own case material, assessment of care was evaluated for five extravasated patients who underwent repeat imaging. Findings reflected results of literature review and included mis- or non-identification of lesions, underestimation of Standardized Uptake Values (SUVs) by 19-73%, classification of scans as non-diagnostic, and the need to repeat imaging with the associated additional radiation exposure, inconvenience, or delays in care. Dosimetry was performed for the same five cases of diagnostic radiopharmaceutical extravasation. Absorbed doses to 5 cm3 of tissue were between 1.1 and 8.7 Gy, and shallow dose equivalent for 10 cm2 of skin was as high as 4.2 Sv. Conclusions: Our findings suggest that significant extravasations can or have caused patient harm and can irradiate patients' tissue with doses that exceed medical event reporting limits and deterministic effect thresholds. Therefore, diagnostic radiopharmaceutical injections should be monitored, and dosimetry of extravasated tissue should be performed in certain cases where thresholds are thought to have been exceeded. Process improvement efforts should be implemented to reduce the frequency of extravasation in nuclear medicine.

Tissue dose estimation after extravasation of 177Lu-DOTATATE

Background

Extravasation of radiopharmaceuticals used for vectorized internal radiotherapy can lead to severe tissue damage (van der Pol et al., Eur J Nucl Med Mol Imaging 44:1234–1243, 2017). Clinical management of these extravasations requires the preliminary estimation of the dose distribution in the extravasation area. Data are scarce regarding the dose estimation in the literature. This work presents a methodology for estimating the dose distribution after an extravasation occurred in September 2017, in the arm of a patient during a 7.4-GBq infusion of Lutathera ® (AAA).

Methods

A local quantification procedure initially developed for renal dosimetry was used. A calibration factor was determined and verified by phantom study. Extravasation volume of interest and its variation in time were determined using 4 whole body (WB) planar acquisitions performed at 2 h (T_2h), 5 h (T_5h), 20 h (T_20h), and 26 h (T_26h) after the beginning of the infusion and three SPECT/CT thoracic acquisitions at T_5h, T_20h, and T_26h. For better estimation of initial extravasation volume, 3 volumes were defined on SPECT images using a 3D activity threshold. Cumulated activities and associated absorbed doses (D₁, D₂, D₃) were calculated in the 3 volumes using the MIRD formalism.

Results

Volumes estimated using 3D threshold were V₁ = 1000 mL, V₂ =400 mL, and V₃ =180 mL. Cumulated activities were evaluated using a monoexponential fit on activities calculated on SPECT images. Estimated local absorbed doses in V₁, V₂, and V₃ were D₁ = 2.3 Gy, D₂ = 4.1 Gy, and D₃ = 6.8 Gy. Evolution in time of local activity in the extravasation area was consistent with an effective local half-life (T_eff) of 2.3 h.

Conclusions

Rapid local dose estimation was permitted thanks to knowledge of the calibration factor determined previous to accidental extravasation. Lutathera® lymphatic drainage was quick in the arm (T_eff = 2.3h). Estimated doses were in the lower range of deterministic effects and far under soft tissue necrosis threshold. Thus, no surgical rinse was proposed. The patient did not show any clinical consequence of the extravasation.

Patient-specific Extravasation Dosimetry Using Uptake Probe Measurements

ABSTRACT

Extravasation is a common problem in radiopharmaceutical administration and can result in significant radiation dose to underlying tissue and skin. The resulting radiation effects are rarely studied and should be more fully evaluated to guide patient care and meet regulatory obligations. The purpose of this work was to show that a dedicated radiopharmaceutical injection monitoring system can help clinicians characterize extravasations for calculating tissue and skin doses. We employed a commercially available radiopharmaceutical injection monitoring system to identify suspected extravasation of 18F-fluorodeoxyglucose and 99mTc-methylene diphosphonate in 26 patients and to characterize their rates of biological clearance. We calculated the self-dose to infiltrated tissue using Monte Carlo simulation and standard MIRD dosimetry methods, and we used VARSKIN software to calculate the shallow dose equivalent to the epithelial basal-cell layer of overlying skin. For 26 patients, injection-site count rate data were used to characterize extravasation clearance. For each, the absorbed dose was calculated using representative tissue geometries. Resulting tissue-absorbed doses ranged from 0.6 to 11.2 Gy, and the shallow dose equivalent to a 10 cm2 area of adjacent skin in these patients ranged from about 0.1 to 5.4 Sv. Extravasated injections of radiopharmaceuticals can result in unintentional doses that exceed well-established radiation protection and regulatory limits; they should be identified and characterized. An external injection monitoring system may help to promptly identify and characterize extravasations and improve dosimetry calculations. Patient-specific characterization can help clinicians determine extravasation severity and whether the patient should be followed for adverse tissue reactions that may present later in time.

Extravasation of [177Lu]Lu-DOTATOC: case report and discussion

Background

In the case of extravasation of radioactive drugs used in peptide-receptor radionuclide therapy of neuroendocrine tumors, or in radionuclide therapy in general, rapid action is important to reduce or avoid complications. The literature on extravasation of drugs for radionuclide therapy is sparse. Based on the present case, we discuss handling and consequences of extravasation. Further, we demonstrate that dosimetry can aid in judging if the treatment of neuroendocrine tumors is satisfactory even after extravasation.

Case presentation

A case of extravasation of [¹⁷⁷Lu]Lu-DOTATOC with a treatment strategy involving exercise and elevation of the affected arm and application of a compression bandage and heating is reported. Redistribution of the drug is verified and quantified by whole-body imaging and quantitative SPECT/CT and measurements of the dose rate at contact with the injection site. [¹⁷⁷Lu]Lu-DOTATOC was redistributed to tumors and organs within 1 day. The patient did not report any discomfort during or after hospitalization, and no side effects related to extravasation were observed. Quantitative SPECT/CT scans at the subsequent treatment cycle of the same patient were analyzed for a comparison between the treatments. Dosimetry showed the treatments were similar with respect to the kidney and tumor absorbed doses. The radiation dose to the epidermal basal layer near the injection site was estimated and found to be consistent with the lack of side effects.

Conclusions

The treatment of extravasation was successful, and the redistribution of the drug can be easily verified through measurement of the dose rate at contact with the skin. From the results of dosimetry, it was assessed that no change of the treatment course was necessary to compensate for a possibly incomplete treatment as a result of the extravasation.

NANETS/SNMMI Procedure Standard for Somatostatin Receptor-Based Peptide Receptor Radionuclide Therapy with 177Lu-DOTATATE

With the recent approval of ¹⁷⁷Lu-DOTATATE for use in gastroenteropancreatic neuroendocrine tumors, access to peptide receptor radionuclide therapy is increasing. Representatives from the North American Neuroendocrine Tumor Society and the Society of Nuclear Medicine and Molecular Imaging collaborated to develop a practical consensus guideline for the administration of ¹⁷⁷Lu-DOTATATE. In this paper, we discuss patient screening, maintenance somatostatin analog therapy requirements, treatment location and room preparation, drug administration, and patient release as well as strategies for radiation safety, toxicity monitoring, management of potential complications, and follow-up. Controversies regarding the role of radiation dosimetry are discussed as well. This document is designed to provide practical guidance on how to safely treat patients with this therapy.

IDACstar: A MCNP Application to Perform Realistic Dose Estimations from Internal or External Contamination of Radiopharmaceuticals

A Monte Carlo-based stand-alone program, IDACstar (Internal Dose Assessment by Computer), was developed, dedicated to perform radiation dose calculations using complex voxel simulations. To test the program, two irradiation situations were simulated, one hypothetical contamination case with 600 MBq of 99mTc and one extravasation case involving 370 MBq of 18F-FDG. The effective dose was estimated to be 0.042 mSv for the contamination case and 4.5 mSv for the extravasation case. IDACstar has demonstrated that dosimetry results from contamination or extravasation cases can be acquired with great ease. An effective tool for radiation protection applications is provided with IDACstar allowing physicists at nuclear medicine departments to easily quantify the radiation risk of stochastic effects when a radiation accident has occurred.

Consequences of radiopharmaceutical extravasation and therapeutic interventions: a systematic review

Purpose

Radiopharmaceutical extravasation can potentially lead to severe soft tissue damage, but little is known about incidence, medical consequences, possible interventions, and effectiveness of these. The aims of this study are to estimate the incidence of extravasation of diagnostic and therapeutic radiopharmaceuticals, to evaluate medical consequences, and to evaluate medical treatment applied subsequently to those incidents.

Methods

A sensitive and elaborate literature search was performed in Embase and PubMed using the keywords “misadministration”, “extravasation”, “paravascular infiltration”, combined with “tracer”, “radionuclide”, “radiopharmaceutical”, and a list of keywords referring to clinically used tracers (i.e. “Technetium-99m”, “Yttrium-90”). Reported data on radiopharmaceutical extravasation and applied interventions was extracted and summarised.

Results

Thirty-seven publications reported 3016 cases of diagnostic radiopharmaceutical extravasation, of which three cases reported symptoms after extravasation. Eight publications reported 10 cases of therapeutic tracer extravasation. The most severe symptom was ulceration. Thirty-four different intervention and prevention strategies were performed or proposed in literature.

Conclusions

Extravasation of diagnostic radiopharmaceuticals is common. ^99mTc, ¹²³I, ¹⁸F, and ⁶⁸Ga labelled tracers do not require specific intervention. Extravasation of therapeutic radiopharmaceuticals can give severe soft tissue lesions. Although not evidence based, surgical intervention should be considered. Furthermore, dispersive intervention, dosimetry and follow up is advised. Pharmaceutical intervention has no place yet in the immediate care of radiopharmaceutical extravasation.

Towards real-time topical detection and characterization of FDG dose infiltration prior to PET imaging

PURPOSE

To dynamically detect and characterize ¹⁸F-fluorodeoxyglucose (FDG) dose infiltrations and evaluate their effects on positron emission tomography (PET) standardized uptake values (SUV) at the injection site and in control tissue.

METHODS

Investigational gamma scintillation sensors were topically applied to patients with locally advanced breast cancer scheduled to undergo limited whole-body FDG-PET as part of an ongoing clinical study. Relative to the affected breast, sensors were placed on the contralateral injection arm and ipsilateral control arm during the resting uptake phase prior to each patient's PET scan. Time-activity curves (TACs) from the sensors were integrated at varying intervals (0-10, 0-20, 0-30, 0-40, and 30-40 min) post-FDG and the resulting areas under the curve (AUCs) were compared to SUVs obtained from PET.

RESULTS

In cases of infiltration, observed in three sensor recordings (30 %), the injection arm TAC shape varied depending on the extent and severity of infiltration. In two of these cases, TAC characteristics suggested the infiltration was partially resolving prior to image acquisition, although it was still apparent on subsequent PET. Areas under the TAC 0-10 and 0-20 min post-FDG were significantly different in infiltrated versus non-infiltrated cases (Mann-Whitney, p < 0.05). When normalized to control, all TAC integration intervals from the injection arm were significantly correlated with SUV_peak and SUV_max measured over the infiltration site (Spearman ρ ≥ 0.77, p < 0.05). Receiver operating characteristic (ROC) analyses, testing the ability of the first 10 min of post-FDG sensor data to predict infiltration visibility on the ensuing PET, yielded an area under the ROC curve of 0.92.

CONCLUSIONS

Topical sensors applied near the injection site provide dynamic information from the time of FDG administration through the uptake period and may be useful in detecting infiltrations regardless of PET image field of view. This dynamic information may also complement the static PET image to better characterize the true extent of infiltrations.

Pitfalls and Limitations of SPECT, PET, and Therapeutic Radiopharmaceuticals

Radiopharmaceuticals are widely accepted to be a very safe class of drugs, with very few adverse reactions and unexpected biodistributions. However, problems can arise because of technical issues in manufacture or reconstitution, patient preparation, or drug administration. This review presents highlights of issues that have arisen in the newer classes of radiopharmaceuticals in the last 20 years and expands the scope of the previous report to include PET and therapeutic radiopharmaceuticals. Variations in the "quality" of the eluate of a (99)Mo/(99m)Tc generator remain a major issue. Several of the newer (99m)Tc tracers require a heating step in preparation that can also lead to unacceptably low radiochemical purity. Radiolytic breakdown can be a problem with all classes of radiopharmaceuticals. Many of the newer radiopharmaceuticals localize by receptor- or transporter-mediated processes and thus can be affected by other drugs, making patient preparation more important than ever. Therapeutic radiopharmaceuticals may require coadministration of radioprotectant regimens, such as the use of lysine-arginine infusions with radiopeptide therapy. Extravasation can have serious consequences with therapeutic radiopharmaceuticals. Adverse reactions to newer radiopharmaceuticals remain rare, though may increase because of coadministration of agents such as contrast media. However, there is known to be underreporting of minor adverse reactions. Knowledge of the pitfalls that can occur with radiopharmaceuticals is important in the interpretation of nuclear medicine images and optimal patient care.

[Extravasation of radiopharmaceuticals: preventive measures and management recommended by SoFRa (Société Française de Radiopharmacie)]

Radiopharmaceuticals extravasation is rare but may have serious clinical issues. Because no specific recommendations are being proposed to date, the goals of our working group created within the French Society of Radiopharmacy are to determine preventive measures and to establish a pragmatic management of extravasation of these drugs. Our preventive measures are to recognize the symptoms (erythema, venous discoloration, swelling), to know the risk factors (which are related to radiopharmaceutical, patient, site of injection, injection technique) and severity (from erythema to skin necrosis, depending on the radionuclide) and how to avoid them (training and awareness of staff, choice of injection site, route of drug administration test, use of a catheter for administration of therapeutic radiopharmaceuticals). Management should be immediate. It can be facilitated by a specific emergency kit. General measures recommended are the immediate cessation of injection, aspiration of fluid extravasation, delimitation of the extravasated area with an indelible pen, informing the doctor. Specific measures taking into account the radiotoxicity of the radionuclide and the type of radiopharmaceutical were also established. The patient should be informed by the doctor about the risks and how to take care of. Traceability of the incident must be ensured. A multidisciplinary reflexion is essential to manage the extravasation as early and effectively as possible.