Clinical Value of 99mTc-3PRGD2 SPECT/CT in Differentiated Thyroid Carcinoma with Negative 131I Whole-Body Scan and Elevated Thyroglobulin Level

Can 99 Tc m -3PRGD 2 (α ν β 3 ) and 18 F-FDG dual-tracer molecular imaging change the therapeutic strategy for progressive refractory differentiated thyroid cancer: Case report

RATIONALE

The management of radioiodine refractory differentiated thyroid cancer (RAIR-DTC) represents a major challenge in thyroid cancer. The American Thyroid Association guidelines recommend the use of tyrosine kinase inhibitors (TKIs) for RAIR-DTC that does not respond to conventional treatment. Currently, imaging modalities that predict the response to TKI treatment based on morphological and functional features are lacking. we report a case of a patient with progressive RAIR lung metastases who underwent 2-deoxy-2-[ 18 F]fluoro-D-glucose and 99technetiumm-three polyethylene glycol spacers-arginine-glycine-aspartic acid ( 99 Tc m -3PRGD 2 ) dual-tracer imaging and investigate the value of this imaging strategy for determining subsequent therapeutic schedules.

PATIENT CONCERNS

A 52-year-old man with advanced RAIR-DTC and progressive lung metastasis. After TKI treatment [sorafenib] lost its clinical benefits, the patient's therapeutic response was evaluated as progressive disease. 2-deoxy-2-[ 18 F]fluoro-D-glucose PET/CT and 99 Tc m -3PRGD 2 SPECT/CT were performed. There were multiple FDG-positive lesions in the lung. However, 99 Tc m -3PRGD 2 SPECT/CT showed only 1 lesion in the right middle pulmonary lobe with arginine-glycine-aspartic positivity.

DIAGNOSIS

RAIR-DTC.

INTERVENTIONS

Radiofrequency ablation was performed for only the lesion with RDG and FDG positivity.

OUTCOMES

The patient quickly achieved partial response.

LESSONS

This case indicates that for progressive RAIR metastases, patients can benefit more from prioritizing treatment for lesions that are both arginine-glycine-aspartic and FDG positive.

Evaluation of integrin αvβ3-targeted imaging for predicting disease progression in patients with high-risk differentiated thyroid cancer (using 99mTc-3PRGD2)

BACKGROUND

High-risk differentiated thyroid cancer (DTC) needs effective early prediction tools to improving clinical management and prognosis. This cohort study aimed to investigate the prognostic impact of ^99mTc-PEG₄-E[PEG₄-c(RGDfK)]₂ (^99mTc-3PRGD₂) SPECT/CT in high-risk DTC patients after initial radioactive iodine (RAI) therapy.

METHODS

Thirty-three patients with high-risk DTC were prospectively recruited; all patients underwent total thyroidectomy and received ^99mTc-3PRGD₂ SPECT/CT before RAI ablation. Follow-up was done with serological and imaging studies. The correlation between ^99mTc-3PRGD₂ avidity and remission rate for initial RAI therapy was evaluated using logistic regression analysis. The prognostic value of ^99mTc-3PRGD₂ SPECT/CT was evaluated by Kaplan-Meier curve and Cox regression analysis.

RESULTS

^99mTc-3PRGD₂ avidity was significantly correlated with the efficacy of initial RAI ablation and an effective predictor for non-remission in high-risk DTC (OR = 9.36; 95% CI = 1.10-79.83; P = 0.041). ^99mTc-3PRGD₂ avidity was associated with poor prognosis in patients with high-risk DTC and an independent prognostic factor for shorter progression-free survival (PFS) (HR = 9.47; 95% CI = 1.08-83.20; P = 0.043). Survival analysis, which was performed between DTC patients with concordant (¹³¹I positive/^99mTc-3PRGD₂ positive) and discordant (¹³¹I negative/^99mTc-3PRGD₂ positive) lesions, indicated that patients with concordant lesions had significantly better PFS than those with discordant lesions (P = 0.022). Moreover, compared with repeated RAI, additional surgery or targeted therapy with multikinase inhibitors could lead to a higher rate of remission in ^99mTc-3PRGD₂-positive patients with progressive disease.

CONCLUSIONS

^99mTc-3PRGD₂ SPECT/CT is a useful modality in predicting progression of the disease after initial RAI and guiding further treatment in high-risk DTC patients.

Sarcoidosis Mimicking Primary Lung Cancer on 99mTc-3PRGD2 Scintigraphy in a PTC Patient

Sarcoidosis is a multi-system disease of unknown etiology that typically occurs in middle-aged adults, often presenting as the formation of granulomas in various organs, including the lungs. Non-typical pulmonary sarcoidosis is rare, and it isnecessary to distinguish its imaging features from lung cancer and tuberculosis. They may appear as an irregular mass with multiple nodules on thoracic computed tomography (CT). In this case, primary lung cancer was suspected in a 57-year-old papillary thyroid carcinoma patient, as the pulmonary lesions were non-radioiodine avid and progressed shortly afterward. The asymmetrical focal uptake that was demonstrated in integrin receptor imaging (99mTc-PEG4-E[PEG4-c(RGDfK)]2 (99mTc-3PRGD2)) warranted flexible-bronchoscope biopsy. Meanwhile, no evidence of malignancy was found, and pathological manifestations led to the subsequent six months of anti-tuberculosis treatment. Combined with the fact that standard anti-tuberculosis showed no improvement, and the patient’s condition was stabilized by corticosteroid treatment alone, a final diagnosis of sarcoidosis was made by an MDT (multidisciplinary consultation). Reported herein is the first case of a hyper vascularization condition within the non-typical asymmetrical sarcoidosis lesions, which should help to establish that the uptake of 3PRDG2 in sarcoidosis can avoid imaging pitfalls.

Advances in Clinical Oncology Research on 99mTc-3PRGD2 SPECT Imaging

The integrin alpha(α)v beta(β)3 receptor is ubiquitous in malignant tumors and has a certain level of specificity for tumors. Technetium-99m hydrazinonicotinamide-dimeric cyclic arginyl-glycyl-aspartic acid peptide with three polyethylene glycol spacers (99mTc-3PRGD2) can bind specifically to the integrin αvβ3 receptor with high selectivity and strong affinity. Thus, it can specifically mark tumors and regions with angiogenesis for tumor detection and be used in single-photon emission computed tomography (SPECT) imaging. This modality has good application value for diagnosing and treating tumor lesions, such as those in the lung, breast, esophagus, head, and neck. This review provides an overview of the current clinical research progress of 99mTc-3PRGD2 SPECT imaging for tumor lesions, including for the diagnosis and differential diagnosis of tumors in different body parts, evaluation of related metastases, and evaluation of efficacy. In addition, the future clinical application prospects and possibilities of 99mTc-3PRGD2 SPECT imaging are further discussed.

Radioiodine adjuvant therapy in differentiated thyroid cancer: An update and reconsideration

Radioiodine (¹³¹I) therapy (RAI) has been utilized for treating differentiated thyroid cancer (DTC) for decades, and its uses can be characterized as remnant ablation, adjuvant therapy (RAT) or treatment for known diseases. Compared with the definite ¹³¹I treatment targets for remnant ablation and known disease, ¹³¹I adjuvant therapy (RAT) aims to reduce the risk of recurrence by destroying potential subclinical disease. Since it is merely given as a risk with no imaging confirmation of persistence/recurrence/metastases, the evidence is uncertain. With limited knowledge and substance, the indication for RAT remains poorly defined for everyday clinical practice, and the benefits of RAT remain controversial. This ambiguity results in a puzzle for clinicians seeking clarity on whether patients should receive RAT, and whether patients are at risk of recurrence/death from undertreatment or adverse events from overtreatment. Herein, we clarified the RAT indications in terms of clinicopathological features, postoperative disease status and response to therapy evaluation, and retrospectively examined the clinical outcomes of RAT as reported in current studies and guidelines. Furthermore, given the evolution of nuclear medicine imaging techniques, it can be expected that the future of RAT may be advanced by nuclear medicine theranostics (i.e., ¹³¹I whole-body scan, PET/CT) by accurately revealing the biological behaviors, as well as the underlying molecular background.

Updated Review of Nuclear Molecular Imaging of Thyroid Cancers

OBJECTIVES

We initiate this comprehensive review to update the advances in this field by objectively elucidating the efficacies of promising radiopharmaceuticals.

METHODS

We performed a comprehensive PUBMED search using the combined terms of "thyroid cancer" and "radiopharmaceuticals" or "nuclear medicine", yielding 3273 and 11026 articles prior to December 31, 2020, respectively.

RESULTS

Based on the mechanism of molecular metabolism, the evaluation of differentiated thyroid cancer and dedifferentiated thyroid cancer is largely centered around radioiodine and fluorine 18 (¹⁸F)-fludeoxyglucose, respectively. Further, ¹⁸F-L-dihydroxyphenylalanine and gallium 68 DOTATATE are the preferred tracers for medullary thyroid cancer. In dedifferentiated medullary thyroid cancer and anaplastic thyroid cancer, ¹⁸F-fludeoxyglucose is superior.

CONCLUSIONS

The future lies in advances in molecular biology, novel radiopharmaceuticals and imaging devices, paving ways to the development of personalized medication for thyroid cancer patients.

Role of [99mTc]Tc-Galacto-RGD2 SPECT/CT in identifying metastatic differentiated thyroid carcinoma after thyroidectomy and radioactive iodine therapy

PURPOSE

Integrin αvβ3, a member of the arginine-glycine-aspartate (RGD)-binding subfamily, is associated with tumor angiogenesis and metastasis. The aim of study is to investigate the clinical role of [^99mTc]Tc-Galacto-RGD₂ SPECT/CT in high-risk differentiated thyroid carcinoma (DTC) after thyroidectomy and radioactive iodine (RAI) therapy.

METHODS

Thirty-six patients with high-risk DTC (20 males, 16 females; mean age: 59.9 ± 16.6 y) who underwent thyroidectomy and RAI therapy were consecutively enrolled in this study. All patients underwent [^99mTc]Tc-Galacto-RGD₂ SPECT/CT and diagnostic ¹³¹I whole-body scan 6 months after the last RAI treatment. A region of interest (ROI) was drawn and the ratio of tumor/non-target (T/NT) was calculated. Per-patient and per-lesion analysis was performed to evaluate the diagnostic efficacy. The final diagnosis was confirmed by histopathology and follow-up. Integrin αvβ3, CD31, and Ki-67 expression in the tumor were also analyzed for evaluation of angiogenesis and proliferation.

RESULTS

Out of 36 patients, twenty-two had metastatic disease. By per-patient analysis, the area under the curve of [^99mTc]Tc-Galacto-RGD₂ SPECT/CT was marginally significantly higher than that of ¹³¹I whole-body scan and morphological imaging (P = 0.0034 and 0.0006). For per-lesion analysis, [^99mTc]Tc-Galacto-RGD₂ SPECT/CT identified 67 metastatic lymph nodes in 14 patients, 12 lung metastases in four patients, and 12 bone metastases in six patients; its sensitivity was significantly higher than that of ¹³¹I whole-body scan in detection of lymphatic (90.54% vs. 55.41%, P = 0.0124) and bone metastasis (92.31% vs. 30.77%, P = 0.046). The ratio of T/NT in metastatic lesions increased with the DTC upstaging.

CONCLUSIONS

[^99mTc]Tc-Galacto-RGD₂ SPECT/CT has high sensitivity in the detection of metastasis in high-risk DTC and further contributes to evaluation of tumor angiogenesis and radio‑iodine refractory status.

An Integrin Alpha 6-Targeted Radiotracer with Improved Receptor Binding Affinity and Tumor Uptake

In this study, we reported a ^99mTc-labeled integrin α₆-targeted peptide as the molecular imaging probe for tumor imaging by single-photon emission computed tomography (SPECT). We found that replacing Cys-Cys cyclized RWY peptide (sequence: cCRWYDENAC) with lactam-bridged cyclic cKiE peptide (sequence: cKRWYDENAisoE) did not sacrifice the integrin α₆-binding affinity and specificity of cKiE radiotracer. To further improve the radiotracer's tumor targeting capability, the dimerized cKiE peptide (termed cKiE2) was designed, and the corresponding radiotracer ^99mTc-cKiE2 was evaluated for tumor uptake and in vivo pharmacokinetics properties in tumor models. We found that cKiE2 showed higher binding affinity to integrin α₆ than did monomeric RWY or cKiE peptide. The biodistribution results showed that the tumor uptake of ^99mTc-cKiE2 was twice higher than that of ^99mTc-RWY (3.20 ± 0.12 vs 1.26 ± 0.06 %ID/g, P < 0.001) at 0.5 h postinjection. The tumor to nontargeting tissue ratios were also enhanced in most normal organs. Specificity of ^99mTc-cKiE2 for integrin α₆ was demonstrated by competitive blocking of tumor uptake with excess cold peptide (3.20 ± 0.24 to 1.38 ± 0.23 %ID/g, P < 0.001). The integrin α₆-positive tumors were clearly visualized by ^99mTc-cKiE2/SPECT with low background except with a relatively high kidney uptake. The tumor uptake of ^99mTc-cKiE2 correlates well with the tumor integrin α₆ expression levels in a linear fashion (R² = 0.9623). We also compared ^99mTc-cKiE2 with an integrin α_vβ₃-targeted radiotracer ^99mTc-3PRGD₂ in the orthotopic hepatocellular carcinoma tumor models. We found that the orthotopic tumor was clearly visualized with ^99mTc-cKiE2. ^99mTc-3PRGD₂ imaging did not show tumor contours in situ as clearly as ^99mTc-cKiE2. The tumor-to-liver ratios of ^99mTc-cKiE2 and ^99mTc-3PRGD₂ were 2.20 ± 0.17 and 0.85 ± 0.20. In conclusion, ^99mTc-cKiE2 is an improved SPECT radiotracer for imaging integrin α₆-positive tumors and has great potential for further clinical application.

68Ga-DOTA-RGD2 Positron Emission Tomography/Computed Tomography in Radioiodine Refractory Thyroid Cancer: Prospective Comparison of Diagnostic Accuracy with 18F-FDG Positron Emission Tomography/Computed Tomography and Evaluation Toward Potential Theranostics

Background: Radioiodine therapy (¹³¹I) forms a principal cornerstone in the management of differentiated thyroid cancer. Radioiodine-refractory differentiated thyroid cancer (RAIR-DTC) presents a challenge in detection of structural disease in patients with evidence of biochemical disease and in treatment of the disease using alternate therapies. The present study was conducted to compare the diagnostic accuracy (in terms of sensitivity and specificity) of ⁶⁸Ga-DOTA-RGD₂ positron emission tomography (PET)/computed tomography (CT) as a neoangiogenesis imaging modality with ¹⁸F-FDG PET/CT, the current standard in diagnostic algorithm of RAIR-DTC, and to evaluate the radiotracer avidity on ⁶⁸Ga-DOTA-RGD₂ PET/CT for potential theranostics. Methods: Forty-four RAIR-DTC patients with negative post-therapy ¹³¹I scan were prospectively enrolled. Serum thyroglobulin (sTg) and anti-thyroglobulin (ATg) measurements were performed with levothyroxine withdrawal (thyrotropin-stimulated state), and ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTA-RGD₂ PET/CT studies were performed within 1 week of each other. Follow-up was performed with histopathology/sTg/ATg/conventional imaging. The findings of ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTA-RGD₂ PET/CT were compared with the reference standard to obtain sensitivity, specificity, and overall accuracy. Degree of radiotracer uptake on ⁶⁸Ga-DOTA-RGD₂ PET/CT was described as tumor to background (T/B) and tumor to liver (T/L) ratios of standardized uptake value. Results:⁶⁸Ga-DOTA-RGD₂ PET/CT detected a total of 123 lesions, with an overall sensitivity, specificity, and accuracy of 82.3%, 100%, and 86.4%, respectively. ¹⁸F-FDG PET/CT detected a total of 144 lesions, with an overall sensitivity, specificity, and accuracy of 82.3%, 50%, and 75%, respectively. Most commonly identified disease sites were nodal metastases (82.9%), followed by thyroid bed lesions (10.5%). 82.1% of patients positive on ⁶⁸Ga-DOTA-RGD₂ PET/CT showed lesional radiotracer uptake higher than the liver (grade IV and grade V). Conclusions:⁶⁸Ga-DOTA-RGD₂ PET/CT showed a similar sensitivity to, but higher specificity and overall accuracy than ¹⁸F-FDG PET/CT in detection of lesions in RAIR-DTC patients. This novel application of the angiogenesis imaging modality can prove useful in RAIR-DTC, especially in patients with negative/suspicious ¹⁸F-FDG PET/CT. Furthermore, since the majority of patients (82.1%) positive on ⁶⁸Ga-DOTA-RGD₂ PET/CT showed radiotracer avidity toward the higher end of the spectrum (grade IV and grade V), novel ¹⁷⁷Lu-based theranostics can be a potential treatment for these patients.

Two is better than one: difunctional high-affinity PSMA probes based on a [CpM(CO)3] (M = Re/99mTc) scaffold

More than 10% of all men will be given the diagnosis "prostate cancer" during their lifetime. Most of the current radio-diagnostic vehicles involve both expensive and localized production with cyclotrons as well as the use of bulky chelators for the radiometal. We report the use of a new multifunctional cyclopentadiene (Cp) platform to prepare difunctional and monofunctional, PSMA-targeting rhenium and technetium-99m complexes. The Cp-complexes and the free ligands are prepared by straightforward functionalization with either one or two Lys-urea-Glu (LuG) PSMA binding motifs. Cell binding assays revealed that the difunctional rhenium complex displays a dissociation constant (KD = 2.1 nM) that is an order of magnitude lower than the monofunctional compound (KD = 24.2 nM). The 99mTc complexes can be prepared in one step and ≤15 min in high yields. These difunctional Cp-Re(i)/99mTc(i) complexes represent a new class of imaging agents with binding affinities comparable to clinically evaluated compounds. Additionally, this study demonstrates that the Cp-platform can readily be derivatized with amine-containing biomolecules. Extending this work to incorporate both targeting and therapeutic moieties could lead to theranostic systems with Re/99mTc.

Identification of Radioactive Iodine Refractory Differentiated Thyroid Cancer

Most differentiated thyroid cancer (DTC) patients have an excellent prognosis. However, about one-third of DTC patients with recurrent or metastatic disease lose the hallmark of specific iodine uptake initially or gradually and acquire radioactive iodine-refractory DTC (RAIR-DTC) with poor prognosis. Due to the potentially severe complications from unnecessarily repeated RAI therapy and encouraging progress of multiple targeted drugs for advanced RAIR-DTC patients, it has become crucial to identify RAIR-DTC early. In this review, we focus on the progress and controversies regarding the defining of RAIR-DTC, further with subsistent approaches and promising molecular nuclear medicine imaging in identifying RAIR-DTC, which may shed light on the proper management methodsof such patients.

Papillary Thyroid Micro Carcinoma: The Incidence of High-Risk Features and Its Prognostic Implications

Background: The current management of papillary thyroid micro carcinoma (PTMC) has become more conservative. However, high-risk characteristics that can only be revealed post-surgically exist. Patients and clinicians need to estimate the risks and understand the prognostic meaning of these factors. Methods: We retrospectively analyzed 246 consecutive patients with PTMC who underwent surgery at our institution between 2015 and 2017. Clinical and histopathological parameters that may indicate recurrent disease were investigated. The responses to therapy in cases with different risks of recurrence were analyzed. Results: A total of 79.26% (195/246) of patients received total thyroidectomy (TT), of whom 177 (90.77%) also received central lymph node dissection. Radioiodine ablation (RAI) was applied in 64.23% (158/246) of patients. Intermediate-high risk features were identified in 27.64% (68/246) after primary treatment. After a median follow-up of 18 months (range, 6-39 months), 121 of 158 (76.58%) patients who received TT+RAI were evaluated as an excellent response. An incomplete response (IR) was observed in 14.56% (23/158) of this group of PTMC. Multivariate analysis identified extra thyroid extension (P = 0.001) and intermediate-high risk stratification (P = 0.014) as significant and independent risk factors for an IR. Conclusions: A total of 27.64% of PTMC cases evaluated as a low risk of recurrence pre-surgery showed intermediate to high risk disease post-surgery, and this leads to a higher rate of IR.

Prognostic Impact of Direct 131I Therapy After Detection of Biochemical Recurrence in Intermediate or High-Risk Differentiated Thyroid Cancer: A Retrospective Cohort Study

Background: Patients treated for intermediate- or high-risk differentiated thyroid carcinoma (DTC) and Thyroglobulin (TG) elevation during follow-up, require a diagnostic whole-body scan (DWBS) and if positive, ¹³¹I treatment. This approach can lead to a delay in treatment and increased costs. The purpose of this study is to compare the oncologic outcomes associated to administration of direct therapy with ¹³¹I at first biochemical recurrence. Methods: Retrospective cohort study of patients with intermediate- or high-risk DTC treated with total thyroidectomy, ¹³¹I ablation and who developed TG elevation during follow-up, between January 2007 and December 2015. Cohort A included patients who underwent a DWBS with 5 mCi of ¹³¹I, and if negative an MRI and/or ¹⁸FDG PET-CT prior to the therapeutic dosage, and cohort B included those who only received a therapeutic dosage of ¹³¹I, without a DWBS or extensive image studies. Main outcomes were second recurrence (SR) and disease-free survival (DFS). The diagnostic accuracy of DWBS was analyzed. Results: Cohorts A and B had 74 and 41 patients, each. By multivariate analysis, age, differentiation grade, TN classification, ablation dose, and performed DWBS (odds ratio 55.1; 95% CI 11.3-269) were associated with SR (p < 0.0001); age, male gender, ablation dose and performed DWBS (hazard ratio 7.79; 95% CI 3.67-16.5) were independent factors associated with DFS (p < 0.0001). DWBS diagnostic accuracy was 36.48%. Conclusion: ¹³¹I treatment in patients with DTC biochemical recurrence and no DWBS or extensive image studies is associated with a significantly lower frequency of SR and an increased DFS. The diagnostic accuracy of DWBS is low, and its clinical efficiency should be defined in prospective phase III studies.

An optimized LC-MS/MS method for determination of HYNIC-3PRGD2, a new promising imaging agent for tumor targeting, in rat plasma and its application

HYNIC-3PRGD₂ is used to prepare a new ^99mTc-radiolabeled tracer. HYNIC-3PRGD₂, which has a high binding affinity for the integrin α_vβ₃ due to its special structure, has become a promising tumor imaging agent for diagnosis and monitor of the clinical response to therapeutic effects of anti-tumor agents. Here, we developed and validated a method for determination of HYNIC-3PRGD₂ concentration in rat plasma using ultra-high performance liquid chromatography-tandem mass spectrometry system. Following sample extraction by methanol precipitation, satisfactory separation through chromatography was achieved on an hydrophilic reverse-phase C₁₈ column AQ (2.1 mm × 100 mm, 2.7 μm) at a flow rate of 0.2 mL·min^-1 with an gradient elution using mobile phase consisting of ultrapure water and acetonitrile fortified with 0.1% formic acid respectively. The calibration curve was developed over a linear range of 3.125-100 ng·mL^-1 with the lower limit of quantification of 3.125 ng·mL^-1. The HYNIC-3PRGD₂ and its internal standard c(RGDfK)(RK5) were detected and quantified with the multiple reaction monitoring (MRM) mode on a triple-quadrupole tandem mass spectrometer. This method was successfully validated and applied for pharmacokinetic evaluation of HYNIC-3PRGD₂ during pre-clinical experiments.