Comparison of 11C-4DST and 18F-FDG PET/CT imaging for advanced renal cell carcinoma: preliminary study

Amino Acid and Proliferation PET/CT for the Diagnosis of Multiple Myeloma

Multiple myeloma (MM) is a hematologic malignancy characterized by infiltration of monoclonal plasma cells in the bone marrow (BM). The standard examination performed for the assessment of bone lesions has progressed from radiographic skeletal survey to the more advanced imaging modalities of computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography/computed tomography (PET/CT). The Durie-Salmon PLUS staging system (upgraded from the Durie-Salmon staging system) applies 2-[18F]-fluoro-2-deoxy-glucose (18F-FDG) PET/CT, and MRI findings to the staging of MM, and 18F-FDG PET/CT has been incorporated into the International Myeloma Working Group (IMWG) guidelines for the diagnosis and staging of MM. However, 18F-FDG PET/CT has significant limitations in the assessment of diffuse BM infiltration and in the differentiation of MM lesions from inflammatory or infectious lesions. The potential of several new PET tracers that exploit the underlying disease mechanism of MM has been evaluated in terms of improving the diagnosis. L-type amino acid transporter 1 (LAT1), a membrane protein that transports neutral amino acids, is associated with cell proliferation and has strong ability to represent the status of MM. This review evaluates the potential of amino acid and proliferation PET tracers for diagnosis and compares the characteristics and accuracy of non-FDG tracers in the management of patients with MM.

Proliferation PET/CT Imaging of Salivary Gland Tumor

Salivary gland tumors are rare neoplasms which vary in terms of origin and malignant potential. 2-[18F]-fluoro-2-deoxy-d-glucose (FDG)-positron emission tomography (PET) has limited ability to differentiate between different types of salivary gland tumors because both Warthin’s tumors and pleomorphic adenomas usually show increased FDG uptake, with no statistically significant difference in standardized uptake value (SUV) compared with malignant salivary gland tumors. Here, we discuss 4′-[methyl-11C]-thiothymidine (4DST) PET, which provides cell proliferation imaging capable of demonstrating intense uptake in parotid carcinoma and Warthin’s tumor, but no uptake in parotid pleomorphic adenoma. This is the first report of the potential of proliferation PET/ computed tomography (CT) imaging for characterizing salivary gland tumors based on the molecular pathogenesis of the tumor.

Cell Proliferation PET Imaging with 4DST PET/CT in Colorectal Adenocarcinoma and Adenoma

An age of 70-year-old man was incidentally found two focal high 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) uptake in the descending colon and in the sigmoid colon. We observed the feature of these two areas in the preplanned 4′-[methyl-11C]-thiothymidine (4DST) positron emission tomography (PET)/computed Tomography (CT)providing cell proliferation imaging. A mass forming high 4DST uptake in the descending colon and focal moderate 4DST uptake in the sigmoid colon was confirmed, and that were proven pathologically as adenocarcinoma and moderate to severe type tubular adenoma, respectively. This is the first report to present that colorectal adenoma can be visualized by proliferation PET imaging and the degree of uptake may enable discrimination of colorectal adenoma from adenocarcinoma, based on pathological considerations.

Carbon-11: Radiochemistry and Target-Based PET Molecular Imaging Applications in Oncology, Cardiology, and Neurology

The positron emission tomography (PET) molecular imaging technique has gained its universal value as a remarkable tool for medical diagnosis and biomedical research. Carbon-11 is one of the promising radiotracers that can report target-specific information related to its pharmacology and physiology to understand the disease status. Currently, many of the available carbon-11 (t_1/2 = 20.4 min) PET radiotracers are heterocyclic derivatives that have been synthesized using carbon-11 inserted different functional groups obtained from primary and secondary carbon-11 precursors. A spectrum of carbon-11 PET radiotracers has been developed against many of the upregulated and emerging targets for the diagnosis, prognosis, prediction, and therapy in the fields of oncology, cardiology, and neurology. This review focuses on the carbon-11 radiochemistry and various target-specific PET molecular imaging agents used in tumor, heart, brain, and neuroinflammatory disease imaging along with its associated pathology.

Efficacy of cell proliferation imaging with 4DST PET/CT for predicting the prognosis of patients with esophageal cancer: a comparison study with FDG PET/CT

PURPOSE

4'-[Methyl-11C] thiothymidine (4DST) incorporates into DNA directly and is a PET tracer used for cell proliferation imaging. The aim of this study was to evaluate the prediction of prognosis with pretreatment 4DST PET/CT compared to fluorodeoxyglucose (FDG) PET/CT in patients with esophageal cancer.

METHODS

In this prospective study, we analyzed 46 patients (68.2 ± 10.0 years old) with pathologically proven esophageal squamous cell cancer who underwent pretreatment 4DST and FDG PET/CT. The maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and total lesion proliferation (TLP) were measured for FDG and 4DST PET. The study endpoints were progression-free survival (PFS) and overall survival (OS). Patients' clinical backgrounds, including age, histological type, clinical stage, and surgical treatment, were adjusted using the Cox proportional-hazards model.

RESULTS

In the follow-up period (median 18.8 (interquartile range: 10.1-29.0) months), 26 and 19 patients showed disease progression and cancer-related death, respectively. After adjusting for clinical variables, only the 4DST parameters (SUVmax (p = 0.001) and TLP (p = 0.022)) were statistically significant for predicting PFS. FDG MTV (p = 0.031), 4DST SUVmax (p = 0.022), and TLP (p = 0.023) were statistically significant for predicting OS. Of the PET parameters, 4DST SUVmax yielded the highest adjusted hazard ratio for both PFS (4.88, 95% confidence intervals (CI): 1.83-12.97) and OS (4.19, 95% CI: 1.23-14.20).

CONCLUSION

Higher accumulation of 4DST in the primary tumor may lead to shorter OS and PFS. 4DST PET/CT is useful for predicting prognosis and may outperform FDG PET/CT.

Clinical value of PET/CT with carbon-11 4DST in the evaluation of malignant and benign lung tumors

OBJECTIVES

The aim of this study was to assess the clinical value of [¹¹C]4DST uptake in patients with lung nodules, including benign and malignant tumors, and to assess the correlation between [¹¹C]4DST uptake and proliferative activity of tumors in comparison with [¹⁸F]FDG uptake.

METHODS

Twenty-six patients (22 males and 4 females, mean age of 65.5-year-old) were analyzed in this prospective study. Patients underwent [¹¹C]4DST and [¹⁸F]FDG PET/CT imaging on the same day. Diagnosis of each lung nodule was confirmed by histopathological examination of tissue specimens at surgery, or during clinical follow-up after the PET/CT studies. To assess the utility of the semi-quantitative evaluation method, the SUV_max was calculated of [¹¹C]4DST and [¹⁸F]FDG uptake by the lesion. Proliferative activities of each tumor as indicated by the immunohistochemical Ki-67 index was also estimated using surgical specimens of patients. Then the relationship between the SUV_max of both PET/CT and the Ki-67 index was examined. Furthermore, the relationship between the uptake of [¹¹C]4DST or [¹⁸F]FDG and the histopathological findings, the clinical stage, and the clinical outcome of patients were also assessed.

RESULTS

There was a positive linear relationship between the SUV_max of [¹¹C]4DST images and the Ki-67 index (Correlation coefficients = 0.68). The SUV_max of [¹¹C]4DST in the 26 lung nodules were 1.65 ± 0.40 for benign lesions, 3.09 ± 0.83 for adenocarcinomas (P < 0.001 between benign and adenocarcinoma), and 2.92 ± 0.58 for SqCCs (P < 0.001 between benign and SqCC). Whereas, the SUVmax of [¹⁸F]FDG were 2.38 ± 2.27 for benign lesions, 6.63 ± 4.24 for adenocarcinomas (n.s.), and 7.52 ± 2.84 for SqCCs (n.s.). The relationship between TNM tumor stage and the SUV_max of [¹¹C]4DST were 2.54 ± 0.37 for T1, 3.48 ± 0.57 for T2, and 4.17 ± 0.72 for T3 (P < 0.005 between T1 and T2, and P < 0.001 between T1 and T3). In comparison with the TNM pathological stage, SUVmax of [¹¹C]4DST were 2.63 ± 0.49 for stage I, 3.36 ± 0.23 for stage II, 3.40 ± 1.12 for stage III, and 4.65 for stage IV (P < 0.05 between stages I and II). In comparison of the clinical outcome, the SUV_max of [¹¹C]4DST were 2.72 ± 0.56 for the no recurrence (No Rec.) group, 3.10 ± 0.33 for the recurrence-free with adjuvant chemotherapy after the surgery (the No Rec. Adjv. CTx. group) and 4.66 ± 0.02 for the recurrence group (Rec. group) (P < 0.001 between the No Rec and Rec. groups, and P < 0.005 between the No Rec. Adjv. CTx. and Rec. groups).

CONCLUSIONS

PET/CT with [¹¹C]4DST is as feasible for imaging of lung tumors as [¹⁸F]FDG PET/CT. For diagnosing lung tumors, [¹¹C]4DST PET is useful in distinguishing benign nodules from malignancies. [¹¹C]4DST uptake in lung carcinomas is correlated with the proliferative activity of tumors, indicating a promising noninvasive PET imaging of DNA synthesis in malignant lung tumors.

4'-[methyl-11C]-thiothymidine as a proliferation imaging tracer for detection of colorectal cancer: comparison with 18F-FDG

OBJECTIVE

The novel radiotracer, 4'-[methyl-¹¹C]-thiothymidine (¹¹C-4DST), was developed based on the DNA incorporation method as a cell proliferation marker. This study investigated the feasibility of ¹¹C-4DST positron emission tomography/computed tomography (PET/CT) for detection of colorectal cancer, as compared with 2-deoxy-2-¹⁸F-fluoro-D-glucose (¹⁸F-FDG) PET/CT, and to correlate the two radiotracers with proliferative activity.

METHODS

A total of 18 patients with newly diagnosed colorectal cancer underwent both ¹¹C-4DST and ¹⁸F-FDG PET/CT. Tumor lesions were identified as areas of focally increased uptake, exceeding that of adjacent normal tissue. For semiquantitative analysis, the maximal standardized uptake value (SUV_max) was calculated. Proliferative activity as quantified by the Ki-67 index was estimated in tumor specimens.

RESULTS

In all 18 patients, colorectal cancers were detected by both ¹¹C-4DST and ¹⁸F-FDG PET/CT. The median (± SD) SUV_max for ¹¹C-4DST (6.02 ± 2.55) was significantly lower than that for ¹⁸F-FDG (13.91 ± 7.62) (P < 0.001). ¹¹C-4DST SUV_max and ¹⁸F-FDG SUV_max showed a significant correlation (r = 0.69, P = 0.002). ¹¹C-4DST SUV_max and Ki-67 index were weakly correlated (r = 0.50, P = 0.04). ¹⁸F-FDG SUV_max and Ki-67 index were not significantly correlated (r = 0.44, P = 0.06).

CONCLUSIONS

Despite a significantly lower uptake of ¹¹C-4DST than that of ¹⁸F-FDG, detection of colorectal cancer was also feasible with ¹¹C-4DST PET/CT. ¹¹C-4DST PET/CT might have a role in the noninvasive assessment of proliferation in colorectal cancer.

Efficacy of 4'-[methyl-11C] thiothymidine PET/CT before and after neoadjuvant therapy for predicting therapeutic responses in patients with esophageal cancer: a pilot study

Background

4′-[Methyl-11C] thiothymidine (4DST) has been introduced as a new cell proliferation imaging PET tracer that incorporates into DNA directly. The aim of this prospective study was to evaluate the efficacy of 4DST PET/CT for predicting responses to neoadjuvant therapy in patients with esophageal cancer comparing with FDG PET/CT.

Methods

Twenty-six patients who had pre- and post-therapeutic 4DST and FDG PET/CT and underwent esophagectomy following neoadjuvant therapy were used for the analysis. Based on pathological findings, patients were divided into two groups: non-responders and responders. The maximum standardized uptake value (SUVmax), metabolic tumor volume, total lesion glycolysis, and total lesion proliferation of the primary lesion were measured for FDG and 4DST PET.

Results

The pathological diagnosis revealed 16 responders and 10 non-responders. Non-responders showed significantly higher 4DST post-therapeutic SUVmax (_postSUVmax) than responders, whereas FDG _postSUVmax showed no statistically significant difference (non-responders vs. responders: 4DST, 6.7 vs. 3.3, p = 0.001; FDG, 6.1 vs. 4.5, p = 0.11). Responders showed a greater reduction in percentage changes of 4DST and FDG SUVmax (ΔSUVmax) from baseline to post-therapeutic PET (non-responders vs. responders: 4DST, − 2.9% vs. − 56.7%, p < 0.001; FDG, − 36.3% vs. − 72.6%, p < 0.001). In ROC analysis, ΔSUVmax and _postSUVmax with 4DST provided great diagnostic performance for predicting responses (area under the curve: 4DST ΔSUVmax = 0.92, 4DST _postSUVmax = 0.88).

Conclusions

4DST PET/CT has a great potential for predicting pathologic response to neoadjuvant therapy in patients with esophageal cancer; it may be slightly superior to that with FDG PET/CT.

18F-FDG and 11C-4DST PET/CT for evaluating response to platinum-based doublet chemotherapy in advanced non-small cell lung cancer: a prospective study

Background

4′-[Methyl-¹¹C] thiothymidine (4DST) PET/CT provides DNA synthesis imaging, which represented a higher correlation with the proliferation in advanced non-small cell lung cancer (NSCLC) than that from imaging with FDG. The aim of this prospective study was to evaluate the potential of 4DST in early therapy monitoring for advanced NSCLC, and to compare the results with those from CT and FDG PET/CT.

Results

Patients who had been pathologically diagnosed with advanced NSCLC and were scheduled to receive platinum-doublet chemotherapy (PT-DC) were eligible. PET/CT imaging with 4DST and with FDG, and CT were performed at baseline and after 2 cycles of PT-DC (interim). Patients were evaluated semi-quantitatively after the 2 cycles of PT-DC using several PET parameters, response evaluation criteria in solid tumors (RECIST) 1.1 based on CT measurements, European Organization for Research and Treatment of Cancer (EORTC) criteria and PET Response Criteria in Solid Tumors (PERCIST) 1.0 based on PET/CT measurements. Baseline measurement data and metabolic response were compared between patients with progression-free survival (PFS) > 4 months and ≤ 4 months, and PFS and overall survival (OS) were compared between patients with and without metabolic response measured with each of the different parameters, using Kaplan-Meier statistics and log-rank testing. A total of 22 patients were included in this study. For predicting PFS > 4 months and ≤ 4 months, metabolic tumor volume (MTV) of baseline 4DST showed the highest area under the curve (0.73), positive predictive value (80.0%), negative predictive value (66.7%), and accuracy (72.7%) among baseline measurement data and metabolic responses from 4DST PET/CT, FDG PET/CT, and CT. Kaplan-Meier curves and log-rank tests for PFS with MTV of baseline FDG and baseline 4DST, and for OS with MTV of baseline FDG and baseline TLG, and MTV of baseline 4DST revealed significant results.

Conclusions

MTV of baseline 4DST PET/CT along with MTV of baseline FDG PET/CT represent promising predictors of PFS, and MTV of baseline 4DST PET/CT along with MTV and TLG of baseline FDG PET/CT are possible predictors of OS in patients with advanced NSCLC.

Renal clear cell carcinoma: diffusion tensor imaging diagnostic accuracy and correlations with clinical and histopathological factors

AIM

To investigate whether diffusion tensor imaging (DTI) can be used to assess renal clinical histopathology, including the nuclear grade (NG), cell density (CD), and the presence of ki-67.

MATERIALS AND METHODS

Thirty patients were enrolled in the study and were confirmed at surgical histopathology to have clear cell renal cell carcinoma (CCRCC). For DTI, a coronal echo-planar imaging sequence was performed (1400 ms repetition time, 76 ms echo time, diffusion direction=6, number of excitations=4; b=0 and 800 s/mm², 6 mm section thickness with no intersection gap). CD and the presence of ki-67 were compared between the different NGs. Correlations between apparent diffusion coefficients (ADCs), E1, fractional anisotropy (FA), CD, and ki-67 were evaluated.

RESULTS

ADC, E1, and FA values are important tools used to identify NG. The cut-off values were 1.003×10^-3 mm²/s, 1.277×10^-3 mm²/s, and 0.218 mm²/s, respectively. The difference between high- and low-grade CD was significant (t=-4.50, p<0.05). Similarly, a significant difference between high and low grade was also found in ki-67 (t=-4.03, p<0.05). ADC, E1, and FA values were decreased with increased CD; a significant negative correlation was found (r=-0.796, -0.865, and -0.996, respectively). Significant negative correlations between ADC, E1, and FA values, and ki-67 were found (r=-0.739, -0.826, and -0.876, respectively).

CONCLUSIONS

DTI can be used to non-invasively assess CCRCC.

Evaluation of DNA synthesis with carbon-11-labeled 4′-thiothymidine

In the cancer research field, the preferred method for evaluating the proliferative activity of cancer cells in vivo is to measure DNA synthesis rates. The cellular proliferation rate is one of the most important cancer characteristics, and represents the gold standard of pathological diagnosis. Positron emission tomography (PET) has been used to evaluate in vivo DNA synthetic activity through visualization of enhanced nucleoside metabolism. However, methods for the quantitative measurement of DNA synthesis rates have not been fully clarified. Several groups have been engaged in research on 4′-[methyl-¹¹C]-thiothymidine (¹¹C-4DST) in an effort to develop a PET tracer that allows quantitative measurement of in vivo DNA synthesis rates. This mini-review summarizes the results of recent studies of the in vivo measurement of cancer DNA synthesis rates using ¹¹C-4DST.