Effects of intratumoral inflammatory process on 18F-FDG uptake: pathologic and comparative study with 18F-fluoro-α-methyltyrosine PET/CT in oral squamous cell carcinoma

Structure-activity characteristics of phenylalanine analogs selectively transported by L-type amino acid transporter 1 (LAT1)

L-type amino acid transporter 1 (LAT1) is a transmembrane protein responsible for transporting large neutral amino acids. While numerous LAT1-targeted compound delivery for the brain and tumors have been investigated, their LAT1 selectivity often remains ambiguous despite high LAT1 affinity. This study assessed the LAT1 selectivity of phenylalanine (Phe) analogs, focusing on their structure-activity characteristics. We discovered that 2-iodo-L-phenylalanine (2-I-Phe), with an iodine substituent at position 2 in the benzene ring, markedly improves LAT1 affinity and selectivity compared to parent amino acid Phe, albeit at the cost of reduced transport velocity. L-Phenylglycine (Phg), one carbon shorter than Phe, was found to be a substrate for LAT1 with a lower affinity, exhibiting a low level of selectivity for LAT1 equivalent to Phe. Notably, (R)-2-amino-1,2,3,4-tetrahydro-2-naphthoic acid (bicyclic-Phe), with an α-methylene moiety akin to the α-methyl group in α-methyl-L-phenylalanine (α-methyl-Phe), a known LAT1-selective compound, showed similar LAT1 transport maximal velocity to α-methyl-Phe, but with higher LAT1 affinity and selectivity. In vivo studies revealed tumor-specific accumulation of bicyclic-Phe, underscoring the importance of LAT1-selectivity in targeted delivery. These findings emphasize the potential of bicyclic-Phe as a promising LAT1-selective component, providing a basis for the development of LAT1-targeting compounds based on its structural framework.

Exploration of the threshold SUV for diagnosis of malignancy using 18F-FBPA PET/CT

Background

The goal of the study was to evaluate the diagnostic ability of 18F-FBPA PET/CT for malignant tumors. Findings from 18F-FBPA and 18F-FDG PET/CT were compared with pathological diagnoses in patients with malignant tumors or benign lesions.

Methods

A total of 82 patients (45 males, 37 females; median age, 63 years; age range, 20–89 years) with various types of malignant tumors or benign lesions, such as inflammation and granulomas, were examined by 18F-FDG and 18F-FBPA PET/CT. Tumor uptake of FDG or FBPA was quantified using the maximum standardized uptake value (SUVmax). The final diagnosis was confirmed by cytopathology or histopathological findings of the specimen after biopsy or surgery. A ROC curve was constructed from the SUVmax values of each PET image, and the area under the curve (AUC) and cutoff values were calculated.

Results

The SUVmax for 18F-FDG PET/CT did not differ significantly for malignant tumors and benign lesions (10.9 ± 6.3 vs. 9.1 ± 2.7 P = 0.62), whereas SUVmax for 18F-FBPA PET/CT was significantly higher for malignant tumors (5.1 ± 3.0 vs. 2.9 ± 0.6, P < 0.001). The best SUVmax cutoffs for distinguishing malignant tumors from benign lesions were 11.16 for 18F-FDG PET/CT (sensitivity 0.909, specificity 0.390) and 3.24 for 18F-FBPA PET/CT (sensitivity 0.818, specificity 0.753). ROC analysis showed significantly different AUC values for 18F-FDG and 18F-FBPA PET/CT (0.547 vs. 0.834, p < 0.001).

Conclusion

18F-FBPA PET/CT showed superior diagnostic ability over 18F-FDG PET/CT in differential diagnosis of malignant tumors and benign lesions. The results of this study suggest that 18F-FBPA PET/CT diagnosis may reduce false-positive 18F-FDG PET/CT diagnoses.

Evaluation of the 18F-FDG-PET/CT uptake association with pathological and immunohistochemistry features in esophagogastric adenocarcinoma

BACKGROUND

The present study aimed to analyze the association between 18F-fluorodeoxyglucose (FDG) uptake and histologic panel in esophagogastric adenocarcinoma.

METHODS

We retrospectively enrolled 26 patients with histologically confirmed esophageal, gastroesophageal junction and gastric adenocarcinoma that have been submitted to pretreatment FDG-PET/CT. We collected the cancer tissue sample of each patient and performed immunohistochemical analyses of the glucose transport protein 1 (GLUT-1), Ki-67, cysteine aspartate-specific proteinases (Caspase)-3 and hexokinase-1, and evaluated the association of these parameters with FDG uptake. The FDG uptake was measured by tumor standardized uptake value (SUV), metabolic tumor volume (MTV), and Total Lesion Glycolysis (TLG). Besides, we analyzed the association of FDG uptake and tumor location, Lauren's histologic subtype, grade of cellular differentiation and intratumoral inflammatory infiltrate.

RESULTS

We found a positive association between GLUT-1 with SUV and TLG, Caspase-3 and SUV and inflammation grade with SUV.

CONCLUSION

Tumor inflammation infiltrate, GLUT-1 and Caspase-3 correlated with 18F-FDG uptake in PET/CT in esophagogastric adenocarcinoma. These findings may help understand the pathologic PET/CT significance in cancer. Understanding the meaning of the 18F-FDG uptake in the field of tumor histologic and immunohistochemistry features is essential to allow the evolution of PET/CT application in esophageal and gastric carcinomas.

18F-FDG PET cannot predict expression of clinically relevant histopathological biomarkers in head and neck squamous cell carcinoma: a meta-analysis

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is a common cancer. Positron emission tomography (PET) with 18F-fluorodeoxyglucose (18F-FDG) is a widely used imaging modality in HNSCC.

PURPOSE

To provide evident data about associations between 18F-FDG PET and histopathology in HNSCC.

MATERIAL AND METHODS

The MEDLINE database was screened for associations between maximum standard uptake values (SUV_max) derived from 18F-FDG PET and histopathological features in HNSCC up to May 2020. Only papers containing correlation coefficients between SUV_max and histopathology were acquired. Overall, 23 publications were collected.

RESULTS

The following correlations were calculated: KI 67: 12 studies (345 patients), pooled correlation coefficient (PCC): 0.23 (95% confidence interval [CI] 0.06-0.40); hypoxia-inducible factor-1α: eight studies (240 patients), PCC: 0.24 (95% CI 0.06-0.42); microvessel density: three studies (64 patients), PCC: 0.33 (95% CI 0.02-0.65); vascular endothelial growth factor: two studies (59 cases), PCC: 0.27 (95% CI 0.02-0.51); tumor suppressor protein p53: four studies (159 patients), PCC: 0.05 (95% CI -0.41 to 0.51); epidermal growth factor receptor: two studies (124 patients), PCC: 0.21 (95% CI 0.05-0.37); tumor cell count: three studies (67 patients), PCC: 0.18 (95% CI -0.06 to 0.42); tumor cell apoptosis: two studies (40 patients), PCC: 0.07 (95% CI = -0.85 to 0.99); B-cell lymphoma-2 protein: two studies (118 patients); PCC: 0.04 (95% CI -0.65 to 0.74); glucose-transporter 1: 10 studies (317 patients), PCC: 0.20 (95% CI 0.10-0.30).

CONCLUSION

SUV_max derived from 18F-FDG PET cannot reflect relevant histopathological features in HNSCC.

Proof of concept of a multimodal intravital molecular imaging system for tumour transpathology investigation

Background

Transpathology highlights the interpretation of the underlying physiology behind molecular imaging. However, it remains challenging due to the discrepancies between in vivo and in vitro measurements and difficulties of precise co-registration between trans-scaled images. This study aims to develop a multimodal intravital molecular imaging (MIMI) system as a tool for in vivo tumour transpathology investigation.

Methods

The proposed MIMI system integrates high-resolution positron imaging, magnetic resonance imaging (MRI) and microscopic imaging on a dorsal skin window chamber on an athymic nude rat. The window chamber frame was designed to be compatible with multimodal imaging and its fiducial markers were customized for precise physical alignment among modalities. The co-registration accuracy was evaluated based on phantoms with thin catheters. For proof of concept, tumour models of the human colorectal adenocarcinoma cell line HT-29 were imaged. The tissue within the window chamber was sectioned, fixed and haematoxylin–eosin (HE) stained for comparison with multimodal in vivo imaging.

Results

The final MIMI system had a maximum field of view (FOV) of 18 mm × 18 mm. Using the fiducial markers and the tubing phantom, the co-registration errors are 0.18 ± 0.27 mm between MRI and positron imaging, 0.19 ± 0.22 mm between positron imaging and microscopic imaging and 0.15 ± 0.27 mm between MRI and microscopic imaging. A pilot test demonstrated that the MIMI system provides an integrative visualization of the tumour anatomy, vasculatures and metabolism of the in vivo tumour microenvironment, which was consistent with ex vivo pathology.

Conclusions

The established multimodal intravital imaging system provided a co-registered in vivo platform for trans-scale and transparent investigation of the underlying pathology behind imaging, which has the potential to enhance the translation of molecular imaging.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05574-y.

Highly Specific L-Type Amino Acid Transporter 1 Inhibition by JPH203 as a Potential Pan-Cancer Treatment

Accelerated cancer cell growth requires a massive intake of amino acids. Overexpression of L-type (large) amino acid transporter 1 (LAT1) on the cancer cell membrane facilitates such a demand, which is limited in normal organs. Therefore, LAT1 overexpression is ideal as a molecular cancer therapeutic target. JPH203, a LAT1-selective non-transportable blocker, had demonstrated LAT1 inhibition in <10 µM IC50 values and effectively suppressed cancer cell growth in studies involving several types of cancer cell lines and tumor xenograft models. A limited phase I clinical trial was performed on five different solid tumors and showed that JPH203 is well-tolerated and has a promising activity for the treatment of bile duct cancer. This review details the development and prospect of JPH203 as a LAT1-targeting cancer therapy.

Clinical Characteristics and Outcome of Pathologic N0 Non-small Cell Lung Cancer Patients With False Positive Mediastinal Lymph Node Metastasis on FDG PET-CT

BACKGROUND/AIM

Preoperative fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET-CT) is a non-invasive and useful diagnostic tool to evaluate mediastinal lymph node (LN) metastasis in lung cancer. However, there are often false-positive LN cases in FDG PET-CT. This study aimed to explore the clinical characteristics and outcome of pathologic N0 non-small cell lung cancer patients with false-positive mediastinal LN on FDG PET-CT.

PATIENTS AND METHODS

We enrolled 147 patients who underwent preoperative FDG PET-CT scan and mediastinal LN dissection. These patients were re-evaluated for post-operative pathologic nodal metastasis and divided into a false-positive group and a group of others.

RESULTS

Among 40 patients diagnosed with clinical N1-3 on FDG PET-CT, 19 (47.5%) patients were pathologic N0, meaning false-positive LN by PET-CT. Preoperative absolute platelet count and platelet-lymphocyte ratio were significantly higher in patients with pathologic N0. The presence of lymphatic invasion was significantly lower in patients with pathologic N0 than in the group of others. Recurrence-free survival was significantly shorter in patients with false positive LN than in patients with true positive LN or true negative LN at the same pathologic stage.

CONCLUSION

Higher absolute platelet count and PLR, lower proportion of lymphatic invasion and shorter recurrence-free survival were associated with false positive mediastinal LN on preoperative FDG PET-CT.

Texture analysis of [18F]-fluorodeoxyglucose-positron emission tomography/computed tomography for predicting the treatment response of postoperative recurrent or metastatic oral squamous cell carcinoma treated with cetuximab

OBJECTIVE

To assess the value of the texture analysis of fluorine-¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) in predicting the treatment response of postoperative recurrent or metastatic oral squamous cell carcinoma (POR/M-OSCC) treated with cetuximab.

METHODS

A total of 14 patients undergoing ¹⁸F-FDG-PET/CT with POR/M-OSCC were divided into the responder and non-responder groups according to cetuximab response by Response Evaluation Criteria in Solid Tumors (RECIST). The regions of interest (ROI) were set at the POR/M-OSCC lesions with the highest uptake of ¹⁸F-FDG, and the volumetric and texture features were analyzed. The features with correlation coefficient of 0.6 or more were further evaluated using the logistic regression analysis to create a model.

RESULTS

The SHAPE_Volume(vx), SHAPE_Volume(mL), metabolic tumor volume (MTV), and gray-level run-length matrix run-length nonuniformity (GLRLM_RLNU) were significantly different between the responder (n = 6) and non-responder (n = 8) groups (p = 0.044, 0.042, 0.047, and 0.012, respectively). The model's area under the curve (AUC) was found to be 0.83, 0.83, 0.79, and 0.92, respectively. The heatmap with PET feature dendrogram showed four distinct clusters including them in patient's responder and non-responder groups.

CONCLUSIONS

Higher MTV, GLRLM_RLNU, SHAPE_Volume(vx), and SHAPE_Volume(mL) in ¹⁸F-FDG-PET images may have the prediction values for treatment response with POR/M-OSCC treated with cetuximab.

Image screening for maxillo-mandibular actinomycosis with CT, 18F-FDG-PET/CT, and 18F-α-methyl tyrosine PET/CT

OBJECTIVES

Clinical features and imaging findings of maxillo-mandibular actinomycosis are similar to those of intraosseous carcinoma. The purpose of this study is to clarify the characteristics of the imaging findings for screening of maxillo-mandibular actinomycosis using CT and PET.

METHODS

Reports on maxillo-mandibular actinomycosis published between 1997 and 2016 were searched in PubMed using "actinomycosis," "maxilla," and "mandibular" as keywords. Ten cases suspected to have malignant tumors on diagnostic imaging findings were selected. In addition, three patients who visited Gunma University Hospital were also included. The 13 total cases were subjected to a pooled analysis of diagnostic screening of maxillo-mandibular actinomycosis using CT, ¹⁸F-FDG-PET/CT (FDG-PET/CT) and ¹⁸F-α-methyl tyrosine PET/CT (FAMT-PET/CT). Additionally, cases of intraosseous carcinoma were analyzed as comparative controls to investigate the difference between maxillo-mandibular actinomycosis and intraosseous carcinoma on CT imaging.

RESULTS

CT images of the 13 cases with maxillo-mandibular actinomycosis were investigated; spotty-type bone resorption was observed in 66.7% (8/12). Moreover, FDG-PET/CT showed abnormal accumulation, but FAMT-PET/CT showed no apparent abnormal accumulation.

CONCLUSIONS

Clinical and imaging findings of maxillo-mandibular actinomycosis are similar to those of intraosseous carcinoma. Differential diagnostic screening can confirm spotty-type bone resorption in cortical bone with CT and specific accumulation in malignant tumors with FAMT-PET/CT. This screening facilitates the rapid implementation of therapeutic interventions.

Associations between FDG-PET and Ki 67-index in head and neck cancer: A meta-analysis

BACKGROUND

FDG-PET might be able to reflect histopathology features of tumors. Ki 67 in head and neck carcinomas (HNSCC). The present study sought to elucidate the association between Ki 67 index and SUVmax based upon a large patient sample.

METHODS

PubMed database was screened for studies analyzed the relationship between Ki 67 and SUV in HNSCC. Nine studies comprising 211 patients were suitable for analysis.

RESULTS

SUVmax increased with tumor grade and was statistically significant different between G1, G2, and G3 tumors. The ROC analysis for discrimination between G1/G2 and G3 tumors revealed an area under curve of 0.71. In the overall patient sample, SUVmax correlated statistically significant with Ki 67 index (r = 0.154, P = .032).

CONCLUSION

The present study identified a weak correlation between SUV values and proliferation index Ki 67 index in HNSCC in a large patient sample. Therefore, SUVmax cannot be used as surrogate parameter for proliferation activity in HNSCC.

Organic Nanotheranostics for Photoacoustic Imaging-Guided Phototherapy

Phototherapies including photothermal therapy (PTT) and photodynamic therapy (PDT) have emerged as one of the avant-garde strategies for cancer treatment. Photoacoustic (PA) imaging is a new hybrid imaging modality that shows great promise for real-time in vivo monitoring of biological processes with deep tissue penetration and high spatial resolution. To enhance therapeutic efficacy, reduce side effects and minimize the probability of over-medication, it is necessary to use imaging and diagnostic methods to identify the ideal therapeutic window and track the therapeutic outcome. With this regard, nanotheranostics with the ability to conduct PA imaging and PTT/PDT are emerging. This review summarizes the recent progress of organic nanomaterials including nearinfrared (NIR) dyes and semiconducting polymer nanoparticles (SPNs) in PA imaging guided cancer phototherapy, and also addresses their present challenges and potential in clinical applications.

18F-FDG and 18F-FAMT PET-derived metabolic parameters predict outcome of oral squamous cell carcinoma

Objectives

L-3-[¹⁸F]-Fluoro-α-methyl tyrosine (FAMT), an amino acid positron emission tomography (PET) tracer, complements [¹⁸F]-fluorodeoxyglucose (FDG) in the diagnosis of malignancies. We compared the predictive ability of FAMT PET versus FDG PET regarding metastatic oral squamous cell carcinoma (OSCC) outcomes for distant metastasis, including lymph node metastasis, and identified the relevant metabolic parameters for each.

Methods

We enrolled 160 patients with OSCC who underwent PET/computed tomography using FDG and FAMT before treatment. Outcomes were assessed using clinicopathological characteristics such as the standardized uptake value (SUV_max, SUV_peak), metabolic tumor volume (MTV), and total lesion glycolysis or total lesion retention. Univariate and multivariate Cox proportional hazards models were used to identify the independent predictors of disease-free survival (DFS) and overall survival (OS) during an average follow-up time of 1401.7 and 1646.0 days, respectively. Areas under the receiver operating characteristic curves were analyzed for the accuracy and predictive value of imaging parameters.

Results

Clinical parameters (excluding age) and PET metabolic parameters were significantly associated with OS. Multivariate analysis showed that an infiltrative growth pattern [p = 0.034, hazard ratio (HR) = 2.30], and the FDG-measured SUV_peak (p = 0.045, HR = 2.45) were independent risk factors for DFS and that lymph node metastasis (p = 0.03, HR = 2.57) and the FAMT-measured MTV (p = 0.004, HR = 3.65) were independent risk factors for OS.

Conclusions

In patients with OSCC, FDG PET predicted DFS, whereas FAMT predicted OS. The two PET tracers, combined with clinical parameters, provide complementary, outcome-related diagnostic information in OSCC.

Peak of Standardized Uptake Value in Oral Cancer Predicts Survival Adjusting for Pathological Stage

BACKGROUND/AIM

To predict survival outcomes of different patients with the same stage of disease is difficult. The possible correlation between ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake parameters and survival outcomes was investigated in oral squamous cell carcinoma patients by multivariate analysis adjusted for the pathological stage according to the 8th edition of the tumor-node-metastasis (TNM) classification of the Union for International Cancer Contro.

PATIENTS AND METHODS

¹⁸F-FDG-uptake parameters of 28 patients were assessed by positron emission tomography with computed tomography (PET/CT).

RESULTS

A peak of standardized uptake value of primary tumor (p-SUVpeak) of ≥14.1 was significantly correlated with shorter overall survival by univariate and multivariate analyses adjusted for the pathological TNM stage. A p-SUVpeak of ≥14.1 was significantly associated with shorter local recurrence-free survival and disease-free survival.

CONCLUSION

A higher p-SUVpeak on pretreatment ¹⁸F-FDG-PET/CT is a prognostic parameter of identifying lower survival outcomes.

Prognostic value of metabolic tumor volume of pretreatment 18F-FAMT PET/CT in non-small cell lung Cancer

Background

This study aimed to determine the prognostic value of positron emission tomography (PET) metabolic parameters—namely metabolic tumor volume (MTV), total lesion glycolysis (TLG), and total lesion retention (TLR)—on fluorine-18 (¹⁸F) fluorodeoxyglucose (FDG) and L- [3-¹⁸F]-α-methyltyrosine (¹⁸F-FAMT) PET/CT in patients with non-small-cell lung cancer (NSCLC).

Methods

The study group comprised 112 NSCLC patients who underwent ¹⁸F-FDG and ¹⁸F-FAMT PET/CT prior to any therapy. The MTV, TLG, TLR, and maximum standardized uptake value (SUV_max) of the primary tumors were determined. Automatic MTV measurement was performed using PET volume computer assisted reading software. (GE Healthcare). Cox proportional hazards models were built to assess the prognostic value of MTV, TLG (for ¹⁸F-FDG), TLR (for ¹⁸F-FAMT), SUV_max, T stage, N stage, M stage, clinical stage, age, sex, tumor histological subtype, and treatment method (surgery or other therapy) on overall survival (OS).

Results

Higher TNM, higher clinical stage, inoperable status, and higher values for all PET parameters (both ¹⁸F-FAMT and ¹⁸F-FDG PET) were significantly associated (P < 0.05) with shorter OS. Multivariate analysis revealed that a higher MTV of ¹⁸F-FAMT (hazard ratio [HR]: 2.88, CI: 1.63–5.09, P < 0.01) and advanced clinical stage (HR: 5.36, CI: 1.88–15.34, P < 0.01) were significant predictors of shorter OS.

Conclusions

MTV of ¹⁸F-FAMT is of prognostic value for OS in NSCLC cases and can help guide decision-making during patient management.

Relation between tumor FDG uptake and hematologic prognostic indicators in stage I lung cancer patients following curative resection

Hematologic parameters of systemic inflammation are receiving attention as promising prognostic indicators in cancer patients. Here, we investigated the relation and compared the prognostic values of circulating blood cell-based parameters and tumor F-fluoro-2-deoxyglucose (FDG) uptake in patients with stage I nonsmall cell lung cancers (NSCLC).Subjects were 1034 patients with newly diagnosed stage I NSCLC who underwent FDG positron emission tomography/computed tomography (PET/CT) followed by curative resection. Total white blood cell (WBC) count, absolute neutrophil, lymphocyte and platelet counts, neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) were obtained. Tumor FDG uptake was measured as SUVmax.WBC, neutrophil and lymphocyte counts, and NLR demonstrated weak but significant correlation to tumor SUVmax. Using the upper quartile as cutoff, patients with high tumor SUVmax had significantly higher WBC, neutrophil and lymphocyte counts, and greater NLR. There were 144 recurrences (13.9%) over a median follow-up of 29.5 months. On Cox proportional hazards regression analysis, WBC count, tumor SUVmax, age, gender, smoking, cell type, and tumor stage were significant univariate prognostic factors. On multivariate analysis, high tumor SUVmax (HR = 2.22; 95% CI, 1.52-3.25; P < 0.001), tumor stage 1B (HR = 2.11; 95% CI, 1.47-3.01; P < 0.001), and old age (HR = 1.03; 95% CI, 1.01-1.05; P = 0.002) were significant independent predictors of poor survival. Finally, high tumor SUVmax remained a significant predictor of prognosis in both low and WBC count groups.Circulating blood counts showed significant correlation to tumor FDG uptake in early stage NSCLC. WBC count was a significant univariate variable, but tumor FDG uptake was a superior and independent predictor of outcome. Hence, tumor FDG uptake effectively stratified prognosis in patients with low as well as high WBC count.

Specific transport of 3-fluoro-l-α-methyl-tyrosine by LAT1 explains its specificity to malignant tumors in imaging

3‐¹⁸F‐l‐α‐methyl‐tyrosine ([¹⁸F]FAMT), a PET probe for tumor imaging, has advantages of high cancer‐specificity and lower physiologic background. FAMT‐PET has been proved useful in clinical studies for the prediction of prognosis, the assessment of therapy response and the differentiation of malignant tumors from inflammation and benign lesions. The tumor uptake of [¹⁸F]FAMT in PET is strongly correlated with the expression of L‐type amino acid transporter 1 (LAT1), an isoform of system L upregulated in cancers. In this study, to assess the transporter‐mediated mechanisms in FAMT uptake by tumors, we examined amino acid transporters for FAMT transport. We synthesized [¹⁴C]FAMT and measured its transport by human amino acid transporters expressed in Xenopus oocytes. The transport of FAMT was compared with that of l‐methionine, a well‐studied amino acid PET probe. The significance of LAT1 in FAMT uptake by tumor cells was confirmed by siRNA knockdown. Among amino acid transporters, [¹⁴C]FAMT was specifically transported by LAT1, whereas l‐[¹⁴C]methionine was taken up by most of the transporters. K_m of LAT1‐mediated [¹⁴C]FAMT transport was 72.7 μM, similar to that for endogenous substrates. Knockdown of LAT1 resulted in the marked reduction of [¹⁴C]FAMT transport in HeLa S3 cells, confirming the contribution of LAT1 in FAMT uptake by tumor cells. FAMT is highly specific to cancer‐type amino acid transporter LAT1, which explains the cancer‐specific accumulation of [¹⁸F]FAMT in PET. This, vice versa, further supports the cancer‐specific expression of LAT1. This study has established FAMT as a LAT1‐specific molecular probe to monitor the expression of a potential tumor biomarker LAT1.

Positron emission tomography-computed tomography versus positron emission tomography-magnetic resonance imaging for diagnosis of oral squamous cell carcinoma: A pilot study

Diagnostic imaging of head and neck cancer has made enormous progress during recent years. Next to morphological imaging modalities (computed tomography [CT] and magnetic resonance imaging [MRI]), there are also hybrid imaging systems that combine functional and morphological information (positron emission tomography [PET]/CT and PET/MRI). The aim of this study was to compare the diagnostic accuracy of PET/MRI in the diagnosis of head and neck cancer with other imaging modalities (MRI, CT, PET/CT). Ten patients (nine male and one female) with histologically proven oral squamous cell carcinoma participated in an 18 F-FDG-PET/CT scan and an additional 18 F-FDG PET/MRI scan prior to surgery. The morphological and functional results were compared with the histological results. Inclusion criteria were histologically proven oral squamous cell carcinoma and no prior surgical intervention, medical therapy, or local external radiation. There was no significant correlation between tumor differentiation and maximum standard uptake values. Functional imaging showed a slightly better correlation with the measurement of the maximal tumor diameter, whereas pure morphological imaging showed a better correlation with the measurement of infiltration depth. Only with PET/MRI could correct lymph node staging be reached; the other imaging tools showed false-negative or false-positive results. In conclusion, we showed in our limited patient cohort that PET/MRI is superior to the morphological imaging modalities, especially for lymph node staging.