99mTc-3PRGD2 SPECT/CT predicts the outcome of advanced nonsquamous non-small cell lung cancer receiving chemoradiotherapy plus bevacizumab

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.

Advantages of 99mTc-3PRGD2 SPECT over CT in the preoperative assessment of lymph node metastasis in patients with esophageal cancer

BACKGROUND

Our study was designed to compare the diagnostic efficacies of integrated ^99mTc-HYNIC-PEG4-E[PEG4-c(RGDfK)]2 (^99mTc-3PRGD₂) single-photon emission computed tomography (SPECT) images and computed tomography (CT) images in lymph node metastasis in the patients with esophageal cancer.

METHODS

From September 2015 and May 2018, 32 patients with histologically proven primary esophageal carcinoma underwent both ^99mTc-3PRGD₂ SPECT and CT scans followed by esophagectomy with lymph node dissection. The results of reviewing ^99mTc-3PRGD₂ SPECT and CT images for the lymph node metastasis were compared in relation with pathologic findings.

RESULTS

During surgery, a total of 168 lymph nodes were dissected in 32 patients, of which 42 node groups in 18 patients were malignant on histologic examination. Preoperative nodal staging was compared with postoperative histopathological staging, The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of ^99mTc-3PRGD₂ SPECT for lymph nodes were 80.95%, 86.51%, 85.12%, 66.67%, and 93.16% on per-node basis, respectively; compared with 59.52%, 73.02%, 69.64%, 42.37%, and 84.40% for CT (p = 0.034, 0.008, 0.005, 0.011, and 0.038, respectively). 70.59% (12/17) false-negative interpretations and 50% (17/34) false-positive interpretations on CT were corrected by ^99mTc-3PRGD₂ SPECT. 37.5% false-negative interpretations on ^99mTc-3PRGD₂ SPECT were corrected by CT. 11.90% (5/42) positive lymph nodes and 13.49% (17/126) negative nodes at pathology were incorrectly diagnosed both by ^99mTc-3PRGD₂ SPECT and CT. The accuracy of ^99mTc-3PRGD₂ SPECT (87.50%, 28/32) was significantly higher than that of CT (62.50, 20/32; p = 0.022) on per-patient basis. ^99mTc-3PRGD₂ SPECT showed significantly higher sensitivity and accuracy in the neck and upper thoracic regions than CT. For nodal staging, ^99mTc-3PRGD₂ SPECT was correct in 78.12% (25/32) of the patients, whereas CT was correct in 53.12% (17/32), p = 0.037.

CONCLUSION

^99mTc-3PRGD₂ SPECT is more accurate than CT for preoperative assessment of lymph node metastasis in esophageal cancer and may be helpful in determining the therapeutic plan.

Integrin αVβ3-targeted SPECT/CT for the assessment of Bevacizumab therapy in orthotopic lung cancer xenografts

The present study aimed to determine the utility of ^99mTc-3PRGD₂ single photon emission computed tomography (SPECT)/computed tomography (CT) for the non-invasive monitoring of the response of integrin α_vβ₃ expression to anti-angiogenic treatment with bevacizumab. Bevacizumab or vehicle therapy was performed in athymic nu/nu mice bearing A549 lung tumors (moderately high integrin α_vβ₃ expression) or PC-3 prostate tumors (low integrin α_vβ₃ expression) at a dose of 1 mg twice a week. The average tumor volume was 180±90 mm³ the day prior to baseline SPECT/CT. Longitudinal ^99mTc-3PRGD₂ SPECT/CT imaging was performed at baseline (-1 day) and at days 5 and 15. Tumors were harvested at all imaging time points for histopathological analysis with hematoxylin and eosin (H&E) and immunohistochemistry staining. Results revealed a significant difference in tumor volume between vehicle- and bevacizumab-treated groups at 5 and 15 days following the start of treatment in the A549 lung model (P<0.05). At 5 days after the start of therapy, the percent injected dose per gram of tissue (%ID/g) and tumor-to-muscle ratio for bevacizumab-treated A549 declined persistently (P<0.05). However, for the vehicle-treated A549 model, the %ID and %ID/g value increased 5 days after the start of treatment (P<0.05). For the PC-3 model, slow-growing tumors and low tumor uptake was observed throughout the study. Alterations in tumor vasculature were confirmed by histopathological H&E analysis and immunohistochemistry. In conclusion, longitudinal imaging using ^99mTc-3PRGD₂ SPECT/CT may be a useful tool for monitoring the anti-angiogenic effect of bevacizumab therapy.

Evaluation of 99mTc-3PRGD2 integrin receptor imaging in hepatocellular carcinoma tumour-bearing mice: comparison with 18F-FDG metabolic imaging

Objective

Our study was designed to explore the utility of ^99mTc-HYNIC-PEG₄-E[PEG₄-c(RGDfK)]₂ (^99mTc-3PRGD₂) for the detection of hepatocellular carcinoma (HCC) and specifically to compare the diagnostic performance of ^99mTc-3PRGD₂ integrin receptor imaging and 2-18-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) metabolic imaging in a nude mouse model.

Methods

^99mTc-3PRGD₂ was synthesized using a HYNIC-3PRGD₂ lyophilized kit with ^99mTcO₄ labelling. The nude mouse animal model was established by subcutaneously injecting 5 × 10⁷/ml HepG2 cells into the shoulder flank of each mouse. Biodistribution studies were performed at 0.5, 1, 2 and 4 h after intravenous administration of 0.37 MBq of ^99mTc-3PRGD₂. Immunohistochemistry was performed to evaluate the expression level of integrin αvβ3 in the HCC tissues. Dynamic imaging was performed using list-mode after the administration of 55.5 MBq of ^99mTc-3PRGD₂, to reconstruct the multiphase images and acquire the best initial scan time. At 8, 12, 16, 20 and 24 days after inoculation with HepG2 cells, 55.5 MBq of ^99mTc-3PRGD₂ and 37 MBq of ¹⁸F-FDG were injected successively into the nude mouse model, subsequently, simultaneous SPECT/PET imaging was performed to calculate the tumour volume and tumour uptake of ^99mTc-3PRGD₂ and ¹⁸F-FDG.

Results

The biodistribution study first validated that the tumour uptake of ^99mTc-3PRGD₂ at the different time points was higher than that of all the other organs tested in the experiment, except for the kidney. Integrin αvβ3 expressed highly in early stage HCC and declined for further necrosis of the tumour tissue. Subcutaneous tumours were visualized clearly with excellent contrast under ^99mTc-3PRGD₂ SPECT/CT imaging, and the multiphase imaging comparison showed the tumours were prominent at 0.5 h, suggesting that the best initial scan time is 0.5 h post-injection. The comparison of the imaging results of the two methods showed that ^99mTc-3PRGD₂ integrin receptor imaging was more sensitive than ¹⁸F-FDG metabolic imaging for the detection of early stage HCC, meanwhile the tumour uptake of ^99mTc-3PRGD₂ was consistently higher than that of ¹⁸F-FDG. However, as tumour necrosis further increased in HCC tissues, the uptake of ¹⁸F-FDG was higher than that of ^99mTc-3PRGD₂.

Conclusion

Our study demonstrated that ^99mTc-3PRGD₂ is a valuable tumour molecular probe for the detection of early stage HCC compared with ¹⁸F-FDG, meriting further investigation of ^99mTc-3PRGD₂ as a novel SPECT tracer for tumour imaging.

(99m)Tc-3PRGD2 SPECT/CT Imaging for Monitoring Early Response of EGFR-TKIs Therapy in Patients with Advanced-Stage Lung Adenocarcinoma

OBJECTIVE

This study was aimed to assess the efficacy of (99m)Tc-3PRGD2 imaging for evaluating both early treatment response to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) and prognosis in advanced-stage lung adenocarcinoma.

MATERIAL AND METHODS

Eighteen patients with lung adenocarcinoma were enrolled for EGFR-TKIs therapy. (99m)Tc-3PRGD2 SPECT/CT and planar imaging were performed pre- and post-therapy. The tumor to nontumor (T/NT) ratio and percentage change in T/NT ratio were assessed for the treatment response. Receiver operator characteristic (ROC) analysis was utilized to analyze the power of identifying responders based on the changes in T/NT ratios.

RESULTS

After treatment, 10 patients had partial response (PR), and 6 patients stable disease (SD), while 2 patients progressive disease (PD). The mean changes in T/NT ratios on SPECT/CT and planar images in PR group were 35.8% and 15.0% and in SD group were 8.9% and 0.7%, while in PD group were 76.1% and 18.7%, respectively. For ROC analysis, using a cutoff value of 23.8% decrease in T/NT ratio on SPECT/CT images, the sensitivity and specificity in identifying responders were 80.0% and 87.5%, respectively. The median progression-free survival (PFS) for patients with responders and nonresponders (on (99m)Tc-3PRGD2 SPECT/CT) was 18 months (95% CI 5.8-30.2 months) and 7 months (95% CI 5.2-8.8 months), respectively (p = 0.006).

CONCLUSION

(99m)Tc-3PRGD2 imaging can evaluate the early response to EGFR-targeted therapy and predict the PFS of lung adenocarcinoma patients.