2-Deoxy-2-[F-18]fluoro-D-glucose-Positron Emission Tomography in Characterization of Solid Renal Masses

Imaging modalities for characterising T1 renal tumours: A systematic review and meta-analysis of diagnostic accuracy

Objectives

International guidelines recommend resection of suspected localised renal cell carcinoma (RCC), with surgical series showing benign pathology in 30%. Non-invasive diagnostic tests to differentiate benign from malignant tumours are an unmet need. Our objective was to determine diagnostic accuracy of imaging modalities for detecting cancer in T1 renal tumours.

Methods

A systematic review was performed for reports of diagnostic accuracy of any imaging test compared to a reference standard of histopathology for T1 renal masses, from inception until January 2023. Twenty-seven publications (including 2277 tumours in 2044 participants) were included in the systematic review, and nine in the meta-analysis.

Results

Forest plots of sensitivity and specificity were produced for CT (seven records, 1118 participants), contrast-enhanced ultrasound (seven records, 197 participants), [99mTc]Tc-sestamibi SPECT/CT (five records, 263 participants), MRI (three records, 220 participants), [18F]FDG PET (four records, 43 participants), [68Ga]Ga-PSMA-11 PET (one record, 27 participants) and [111In]In-girentuximab SPECT/CT (one record, eight participants). Meta-analysis returned summary estimates of sensitivity and specificity for [99mTc]Tc-sestamibi SPECT/CT of 88.6% (95% CI 82.7%-92.6%) and 77.0% (95% CI 63.0%-86.9%) and for [18F]FDG PET 53.5% (95% CI 1.6%-98.8%) and 62.5% (95% CI 14.0%-94.5%), respectively. A comparison hierarchical summary receiver operating characteristic (HSROC) model did not converge. Meta-analysis was not performed for other imaging due to different thresholds for test positivity.

Conclusion

The optimal imaging strategy for T1 renal masses is not clear. [99mTc]Tc-sestamibi SPECT/CT is an emerging tool, but further studies are required to inform its role in clinical practice. The field would benefit from standardisation of diagnostic thresholds for CT, MRI and contrast-enhanced ultrasound to facilitate future meta-analyses.

Emerging Novel Functional Imaging and Immunotherapy in Renal Cell Carcinoma and Current Treatment Sequencing Strategies After Immunotherapy

The management of renal cell carcinoma (RCC) has advanced significantly in the past two decades. Many promising functional imaging modalities such as radiolabeled tracer targeting carbonic anhydrase IX and prostate-specific membrane antigen are under development to detect primary kidney tumors, stage systemic disease, and assess treatment response in RCC. Immune checkpoint inhibitors targeting PD-1 and cytotoxic T-cell lymphocyte-4 have changed the treatment paradigm in advanced RCC. Trials investigating novel mechanisms such as LAG-3 immune checkpoint inhibition, chimeric antigen receptor T-cell therapies, and T-cell engagers targeting RCC-associated antigens are currently ongoing. With the rapidly changing treatment landscape of RCC, the treatment sequence strategies will continue to evolve. Familiarity with the toxicities associated with the therapeutic agents and how to manage them are essential to achieve optimal patient outcomes. This review summarizes the recent developments of functional imaging and immunotherapy strategies in RCC, and the evidence supports treatment sequencing.

FDG PET/CT in Solitary Isolated Renal Metastasis From Squamous Cell Lung Cancer

ABSTRACT

We describe FDG PET/CT findings in a patient with a solitary isolated renal metastasis from squamous cell lung cancer. The renal metastasis appeared as a small focus of activity at the renal cortex on FDG PET/CT at initial staging of the lung tumor, misinterpreted as cortical tracer retention, and was significantly enlarged on the second FDG PET/CT performed 4 months after the first PET/CT. This case demonstrates the usefulness of FDG PET/CT in identifying unexpected extrathoracic metastasis from lung cancer. Focal FDG uptake in the renal cortical region in a cancer patient should be evaluated carefully to avoid misdiagnosis.

High Prognostic Value of 68Ga-PSMA PET/CT in Renal Cell Carcinoma and Association with PSMA Expression Assessed by Immunohistochemistry

In oligo-metastatic renal cell carcinoma (RCC), neither computed tomography (CT) nor bone scan is sensitive enough to detect small tumor deposits hampering early treatment and potential cure. Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein expressed in the neo-vasculature of numerous malignant neoplasms, including RCC, that can be targeted by positron emission tomography (PET) using PSMA-targeting radioligands. Our aim was to investigate whether PSMA-expression patterns of renal cancer in the primary tumor or metastatic lesions on immunohistochemistry (IHC) are associated with PET/CT findings using [68Ga]-PSMA-HBED-CC (PSMA-PET/CT). We then analyzed the predictive and prognostic role of the PSMA-PET/CT signal. In this retrospective single-center study we included patients with renal cancer submitted to PSMA-PET/CT for staging or restaging, with tumor specimens available for PSMA-IHC. Clinical information (age, tumor type, and grade) and IHC results from the primary tumor or metastases were collected. The intensity of PSMA expression at IHC was scored into four categories: 0: none; 1: weak; 2: moderate; 3: strong. PSMA expression was also graded according to the proportion of vessels involved (PSMA%) into four categories: 0: none; 1: 1-25%; 2: 25-50%; 3: >50%. The intensity of PSMA expression and PSMA% were combined in a three-grade score: 0-2 absent or mildly positive, 3-4 moderately positive, and 5-6 strongly positive. PSMA scores were used for correlation with PSMA-PET/CT results. Results: IHC and PET scans were available for the analysis in 26 patients (22 ccRCC, 2 papillary RCC, 1 chromophobe, 1 "not otherwise specified" RCC). PSMA-PET/CT was positive in 17 (65%) and negative in 9 patients (35%). The mean and median SUVmax in the target lesion were 34.1 and 24.9, respectively. Reporter agreement was very high for both distant metastasis location and local recurrence (kappa 1, 100%). PSMA-PET detected more lesions than conventional imaging and revealed unknown metastases in 4 patients. Bone involvement, extension, and lesion number were greater than in the CT scan (median lesion number on PET/CT 3.5). The IHC PSMA score was concordant in primary tumors and metastases. All positive PSMA-PET/CT results (15/22 ccRCC, 1 papillary cancer type II, and 1 chromofobe type) were revealed in tumors with strong or moderate PSMA combined scores (3-4 and 5-6). In ccRCC tissue samples, PSMA expression was strong to moderate in 20/22 cases. The SUVmax values correlated to the intensity of PSMA expression which were assessed using IHC (p = 0.01), especially in the ccRCC subgroup (p = 0.009). Median survival was significantly higher in patients with negative PSMA-PET/CT (48 months) compared to patients with a positive scan (24 months, p= 0.001). SUVmax ≥ 7.4 provides discrimination of patients with a poor prognosis. Results of PSMA-PET/CT changed treatment planning. Conclusions: in renal cancer, positive PSMA-PET/CT is strongly correlated to the intensity of PSMA expression on immunohistochemistry in both ccRCC and chromophobe cancer. PSMA-PET/CT signal predicts a poor prognosis confirming its potential as an aggressiveness biomarker and providing paramount additional information influencing patient management.

Utility of Fluorine18 Fluoro-2-deoxy-D-glucose Positron Emission Tomography/Computed Tomography in Metabolic Characterization of Solid Renal Mass Lesion and Localization of Extra Renal Lesions in the Body - A Prospective Study from the Tertiary Care Center in South India

Purpose of the Study

Renal mass lesions in majority of the cases are due to malignant etiology and about one-third of them are reported with metastatic lesions at the time of presentation. Thus proper investigational workup is needed for staging and thereby treatment planning. The current fluorine18 fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (F18-FDG PET/CT) study was designed to characterize renal mass lesions metabolically and identifying other metabolically active lesions in the body suggesting metastatic disease.

Materials and Methods

A total of 24 patients (males - 18 and females - 6) with a mean age of 53.8 ± 12.3 years were recruited in this study for dual time-point PET/CT scan. All patients with renal mass lesions underwent contrast-enhanced CT prior to PET/CT. Metabolic parameters such as maximum standardized uptake value (max.SUV) with a cut off ≥2.5 and retention index (RI) of ≥10% were used to label the lesion as malignant and remaining less than cutoff as benign. The final diagnosis of lesion on imaging was confirmed with a histopathological examination (HPE).

Results

Using max.SUV cut off value, 17/24 renal mass lesions were characterized as malignant and remaining 7/24 renal lesions of benign etiology. PET/CT showed sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 80%, 75%, 94.1%, 42.8%, and 79.1%, respectively, by considering HPE as a gold standard. Nine patients were diagnosed with distant site involvement suggestive of metastases.

Conclusion

F18-FDG PET/CT can efficiently characterize solid renal mass lesion as benign and malignant using metabolic parameters such as max.SUV and RI. In addition, whole-body survey identified distant site involvement in 25% of the patients, thus contributing change in management.

FDG PET/CT in Unilateral Renal Metastasis From Colon Cancer

ABSTRACT

Renal metastasis from colon cancer is rare. We describe FDG PET/CT findings in a case with a right renal and a postcaval lymph node metastasis from colon cancer. Both the renal tumor and postcaval lymph node showed increased FDG uptake with SUVmax of 6.1 for the renal tumor and 5.5 for the postcaval lymph node. The imaging findings mimicked a primary renal cancer with postcaval lymph node metastasis.

FDG PET/CT in a Case With Cellular Schwannoma of the Kidney

ABSTRACT

Schwannoma of the kidney is exceedingly rare. We describe contrast-enhanced CT and FDG PET/CT findings in a case with renal cellular schwannoma. Contrast-enhanced CT showed the enhancing tumor was located in the anterior middle portion of the left kidney, encasing the renal vessels and compressing the renal pelvis. The tumor showed inhomogeneous FDG uptake with SUVmax of 8.6 mimicking renal cell carcinoma. This case indicates renal schwannoma should be included in the differential diagnosis of FDG-avid renal lesions.

99mTc-MIBI SPECT/CT and FDG PET/CT in Isolated Bilateral Renal Metastases From Adenoid Cystic Carcinoma of the Maxilla

ABSTRACT

Renal metastasis from adenoid cystic carcinoma of the head and neck is uncommon. We present 99mTc-MIBI SPECT/CT and FDG PET/CT findings in a case with isolated bilateral renal metastases from adenoid cystic carcinoma of the left maxilla. The metastatic adenoid cystic carcinomas of the kidneys showed photopenia on 99mTc-MIBI SPECT/CT and increased FDG uptake on FDG PET/CT mimicking primary renal cell carcinoma.

Chromophobe Renal Cell Carcinoma with Radiologic-Pathologic Correlation

Renal cell carcinoma (RCC) is a heterogeneous group of neoplasms derived from the renal tubular epithelial cells. Chromophobe RCC (chRCC) is the third most common subtype of RCC, accounting for 5% of cases. chRCC may be detected as an incidental finding or less commonly may manifest with clinical symptoms. The mainstay of therapy for chRCC is surgical resection. chRCC has a better prognosis compared with the more common clear cell RCC. At gross pathologic analysis, chRCC is a solid well-defined mass with lobulated borders. Histologic findings vary by subtype but include large pale polygonal cells with abundant transparent cytoplasm, crinkled "raisinoid" nuclei with perinuclear halos, and prominent cell membranes. Pathologic analysis reveals only moderate vascularity. The most common imaging pattern is a predominantly solid renal mass with circumscribed margins and enhancement less than that of the renal cortex. The authors discuss chRCC with emphasis on correlative pathologic findings and illustrate the multimodality imaging appearances of chRCC by using cases from the Radiologic Pathology Archives of the American Institute for Radiologic Pathology. ^©RSNA, 2021.

Role of positron emission tomography/computed tomography in the evaluation of renal cell carcinoma

Introduction:

Positron emission tomography (PET) is not a standard recommendation in most of the major guidelines for the evaluation of renal cell carcinoma (RCC). Earlier studies evaluating PET scan in patients with RCC have provided discordant results. However, with the advent of newer hybrid PET/computed tomography (CT) scanning systems, this modality has shown increased efficacy in the evaluation of primary renal masses along with the detection of extrarenal metastases, restaging recurrent RCC, and also in monitoring response to targeted therapy. We performed a systematic review of the existing literature on the role of PET scan in the evaluation of RCC.

Methodology:

We systematically searched the databases of PubMed/Medline, Embase, and Google Scholar to identify studies on the use of PET scan in RCC. Using Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines, 94 full-text articles were selected, of which 54 relevant articles were then reviewed, after a consensus by the authors.

Results:

Several studies have shown similar sensitivity and specificity of fluoro-2-deoxy-2-d-glucose-PET (FDG-PET) scan as compared to conventional CT scan for the initial diagnosis of RCC, and an improved sensitivity and specificity for the detection of metastases and recurrences following curative therapy. The PET scan may also play a role in predicting the initial tumor biology and pathology and predicting the prognosis as well as the response to therapy.

Conclusion:

The current guidelines do not recommend PET scan in the staging armamentarium of RCCs. However, FDG-PET scan is as efficacious, if not better than conventional imaging alone, in the evaluation of the primary and metastatic RCC, as well as in evaluating the response to therapy, due to its ability to pick up areas of increased metabolic activity early on. Newer tracers such as ^Ga68 prostate specific membrane antigen-labeled ligands may help in opening up newer avenues of theragnostics.

Prognostic value of maximum standard uptake value, metabolic tumor volume, and total lesion glycolysis of 18F-FDG PET/CT in patients with renal carcinoma: A protocol for systematic review and meta analysis

PURPOSE

We present a comprehensive systematic review of the documented literature on parameters derived from F-fluorodeoxyglucose positron emission tomography (F-FDG PET) and meta-analysis of the prognostic value of maximal standard uptake value (SUVmax), metabolic tumor volume (MTV) and total lesional glycolysis (TLG) in patients with renal carcinoma (RCC).

PATIENTS AND METHODS

Relevant articles in English from PubMed, EMBASE, and the Cochrane Library were retrieved. Pooled hazard ratio (HR) values were used to assess the prognostic value of SUVmax, MTV, and TLG.

RESULTS

A total of 10 primary studies involving 780 patients with RCC were included. The combined HRs for event-free survival were 1.32 (95% CI 1.10-1.58) for SUVmax, 2.40 (95% CI 1.20-4.79) for MTV, and 3.31 (95% CI 1.68-6.50) for TLG. Pooled HRs for overall survival were 1.264 (95% CI 1.124-1.421) for SUVmax, 3.52 (95% CI 1.451-8.536) for MTV, and 6.33 (95% CI 1.32-30.30) for TLG. Subgroup analysis revealed SUVmax as an independent risk factor for patients with recurrence or metastasis.

CONCLUSION

The present meta-analysis confirmed that despite the clinical heterogeneity of RCC and adoption of various methods between studies, high SUVmax is a significant prognostic factor, especially in patients with recurrence or metastasis. MTV and TLG were associated with prediction of higher risk of adverse events or death in patients with RCC.

Role of Positron Emission Tomography Imaging in Metabolically Active Renal Cell Carcinoma

PURPOSE OF REVIEW

The clinical role of fluorine-18 fluoro-2-deoxyglucose (FDG)-positron emission tomography (PET) in renal cell carcinoma (RCC) is still evolving. Use of FDG PET in RCC is currently not a standard investigation in the diagnosis and staging of RCC due to its renal excretion. This review focuses on the clinical role and current status of FDG PET and PET/CT in RCC.

RECENT FINDINGS

Studies investigating the role of FDG PET in localized RCC were largely disappointing. Several studies have demonstrated that the use of hybrid imaging PET/CT is feasible in evaluating the extra-renal disease. A current review of the literature determines PET/CT to be a valuable tool both in treatment decision-making and monitoring and in predicting the survival in recurrent and metastatic RCC. PET/CT might be a viable option in the evaluation of RCC, especially recurrent and metastatic disease. PET/CT has also shown to play a role in predicting survival and monitoring therapy response.

Differential diagnostic ability of 18F-FDG PET/CT radiomics features between renal cell carcinoma and renal lymphoma

BACKGROUND

The aim of this study is to determine the differential diagnostic value of texture parameters of PET/CT on renal cell carcinoma and renal lymphoma.

METHODS

Twenty renal lymphoma and 18 renal cell carcinoma (RCC) patients were analyzed in this study. The pathological information and basic characteristics were extracted from the electronic medical record system of our hospital. We used LIFEx package to extract data from the radiomics images. Receiver operating characteristic analysis and binary logistic regression analysis was applied in determining the diagnostic accuracy of texture parameters as well as the synthetic parameter, of which the sensitivity and specificity was improved.

RESULTS

There were 14 (two in Histogram, two in Grey Level Co-occurrence Matrix, five in Grey-Level Run Length Matrix, five in Grey-Level Zone Length Matrix) out of the texture parameters showing an area under the curve (AUC) >0.7 and P<0.05. Synthesized parameters of each section showed even higher differentiation ability, with AUC varying from 0.725 to 1.000.

CONCLUSIONS

Texture analysis of ¹⁸F-FDG PET/CT could effectively differentiate between RCCs and renal lymphomas.

Extensive Metastatic Sarcomatoid Renal Cell Carcinoma Evaluated by 18F-FDG PET/CT: a Case Report and Review of Literature

Sarcomatoid renal cell carcinoma (sRCC) is a highly aggressive form of dedifferentiated renal cell carcinoma. We report a 62-year-old man who presented with respiratory symptoms and a lung mass on chest computed tomography (CT). The patient underwent positron emission tomography/computed tomography (PET/CT) with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and was found to have extensive metastatic disease. Based on the history and imaging findings, there were possible primary malignancies, including bronchogenic carcinoma, melanoma, or an aggressive lymphoma. An excisional biopsy surprisingly revealed a high-grade sarcomatoid carcinoma with no evidence of differentiation, and immunohistochemical (IHC) studies showed that the tumor cells were positive for markers of genitourinary origin (PAX-8 and vimentin). The histologic and IHC results, along with multiple FDG-avid exophytic lesions in both kidneys, were considered diagnostic of sRCC. Here we have highlighted the potential role of ¹⁸F-FDG-PET-CT in patients with sRCC, discussed the diagnostic challenges, and presented a brief review.

The Role of PET Scanning in the Evaluation of Patients With Kidney Disease

Patients with underlying kidney disease are often required to undergo imaging for a variety of purposes including diagnosis and prognosis. A test that is being increasingly used with for this group of patients is the positron emission test (PET) scan. In addition, combining the nuclear medicine technique (PET) with computed tomography scan allows additional imaging advantages over either alone. These imaging modalities are commonly used for a number of extrarenal indications (ie, cancer, coronary artery disease, central nervous system disease, infectious diseases, and others). They have also been used for diagnosis of acute tubulointerstitial nephritis, evaluation and management of retroperitoneal fibrosis, identifying infection within kidney and liver cysts, and distinguishing complex kidney cysts from kidney cancer in patients with underlying CKD. We will review PET scan utility in patients with kidney disease.

Fat-Containing Hypermetabolic Masses on FDG PET/CT: A Spectrum of Benign and Malignant Conditions

OBJECTIVE

This article focuses on identifying the imaging appearances of hypermetabolic fatty masses and masslike lesions on PET/CT and understanding the diagnostic challenges radiologists may face while interpreting findings of these lesions on PET/CT. This article provides an approach to aid in the diagnosis of these lesions and the appropriate management of patients.

CONCLUSION

Both malignant and benign fat-containing masses and masslike lesions can show hypermetabolic activity on PET/CT. Although the differential diagnosis is broad, clinical history, anatomic location, and knowledge of anatomic variants and imaging features can help radiologists avoid misinterpretation of benign fatty lesions as malignancy.

The Place of FDG PET/CT in Renal Cell Carcinoma: Value and Limitations

Unlike for most other malignancies, application of FDG PET/CT is limited for renal cell carcinoma (RCC), mainly due to physiological excretion of 18F-fluoro-2-deoxy-2-d-glucose (FDG) from the kidneys, which decreases contrast between renal lesions and normal tissue, and may obscure or mask the lesions of the kidneys. Published clinical observations were discordant regarding the role of FDG PET/CT in diagnosing and staging RCC, and FDG PET/CT is not recommended for this purpose based on current national and international guidelines. However, quantitative FDG PET/CT imaging may facilitate the prediction of the degree of tumor differentiation and allows for prognosis of the disease. FDG PET/CT has potency as an imaging biomarker to provide useful information about patient’s survival. FDG PET/CT can be effectively used for postoperative surveillance and restaging with high sensitivity, specificity, and accuracy, as early diagnosis of recurrent/metastatic disease can drastically affect therapeutic decision and alter outcome of patients. FDG uptake is helpful for differentiating benign or bland emboli from tumor thrombosis in RCC patients. FDG PET/CT also has higher sensitivity and accuracy when compared with bone scan to detect RCC metastasis to the bone. FDG PET/CT can play a strong clinical role in the management of recurrent and metastatic RCC. In monitoring the efficacy of new target therapy such as tyrosine kinase inhibitors (TKIs) treatment for advanced RCC, FDG PET/CT has been increasingly used to assess the therapeutic efficacy, and change in FDG uptake is a strong indicator of biological response to TKI.

Preoperative evaluation of renal cell carcinoma by using 18F-FDG PET/CT

PURPOSE

This study aimed to characterize the FDG uptake of renal cell carcinoma (RCC) by the pathological subtype and nuclear grade.

PATIENTS AND METHODS

We retrospectively identified patients who underwent F-FDG PET and subsequent partial or radical nephrectomy for renal tumors. The relationships of the SUV of renal tumor with subtypes, nuclear grade, and clinicopathological variables were investigated.

RESULTS

Ninety-two tumors were analyzed, including 52 low-grade (G1 and G2) and 18 high-grade (G3 and G4) clear cell RCC; 7 chromophobe, 5 papillary, and 1 unclassified RCC; and 9 benign tumors (7 angiomyolipoma and 2 oncocytoma). The SUVs of high-grade clear cell RCC (mean ± SD, 6.8 ± 5.1) and papillary RCC (6.6 ± 3.7) were significantly higher than that of the controls (2.2 ± 0.3). The SUV of high-grade clear cell RCC was higher than that of low-grade tumors (median, 4.0 vs. 2.2; P < 0.001). The optimal SUV cutoff value of 3.0 helped to differentiate high-grade from low-grade clear cell RCC, with 89% sensitivity and 87% specificity. On multiple regression analysis, a high grade was the most significant predictor of SUV for clear cell RCC.

CONCLUSIONS

FDG uptake higher than that observed in normal kidney tissues suggests a high-grade clear cell RCC or papillary RCC subtype. FDG-PET using SUV may have a role in prediction of pathological grade of renal tumor.

Renal Cell Carcinoma with Paraneoplastic Manifestations: Imaging with CT and F-18 FDG PET/CT

We present a case of renal cell carcinoma with prominent inflammatory and paraneoplastic manifestations. The initial CT detection of renal malignancy and subsequent post-therapeutic F-18 FDG PET/CT diagnosis of occult osseous metastasis were based on the patient's anemia, thrombocytosis and abnormally increased levels of serum C-reactive protein.

FDG and FLT-PET for Early measurement of response to 37.5 mg daily sunitinib therapy in metastatic renal cell carcinoma

BACKGROUND

Metastatic renal cell carcinoma has a poor prognosis and an intrinsic resistance to standard treatment. Sunitinib is an oral receptor tyrosine kinase inhibitor that has been used as a first-line targeted therapy in metastatic renal cell carcinoma. While computed tomography (CT) is currently the gold standard for response assessment in oncological trials, numerous studies have shown that positron emission tomography (PET) imaging can provide information predictive of tumor response to treatment earlier than the typical interval for standard of care follow-up CT imaging. In this exploratory study we sought to characterize early tumor response in patients with metastatic renal cell carcinoma treated with continuous daily 37.5 mg sunitinib therapy.

METHODS

Twenty patients underwent dynamic acquisition positron emission tomography (PET) imaging using (18) F-fluorodeoxyglucose (FDG) and (18) F-fluorothymidine (FLT) at baseline and early in treatment (after 1, 2, 3 or 4 weeks) with 37.5 mg continuous daily dosing of sunitinib. Semi-quantitative analyses were performed to characterize the tumor metabolic (FDG) and proliferative (FLT) responses to treatment.

RESULTS

Proliferative responses were observed in 9/19 patients and occurred in 2 patients at one week (the earliest interval evaluated) after the initiation of therapy. A metabolic response was observed in 5/19 patients, however this was not observed until after two weeks of therapy were completed. Metabolic progression was observed in 2/19 patients and proliferative progression was observed in 1/19 patients. Baseline FDG-PET tumor maximum standardized uptake values correlated inversely with overall survival (p = 0.0036). Conversely, baseline (18) F-fluorothymidine PET imaging did not have prognostic value (p = 0.56) but showed a greater early response rate at 1-2 weeks after initiating therapy.

CONCLUSIONS

While preliminary in nature, these results show an immediate and sustained proliferative response followed by a delayed metabolic response beginning after two weeks in metastatic renal cell carcinoma treated with a continuous daily dose of 37.5 mg sunitinib. The results provide evidence of tumor response to lower-dose sunitinib while also supporting the inclusion of PET imaging as a tool for early assessment in oncological clinical trials.

TRIAL REGISTRATION

ID: NCT00694096.

Standardized uptake values highly correlate with tumor size and Fuhrman grade in patients with clear cell renal cell carcinoma

BACKGROUND

We investigated the correlation between standardized uptake value (SUVmax), tumor size and Fuhrman grade in patients with renal cell carcinoma (RC).

MATERIALS AND METHODS

We retrospectively analyzed the data of 54 patients with clear cell renal cell carcinoma histopathologically diagnosed who underwent fluorine-18 fluoro-2 deoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) between January 2005 and March 2014.

RESULTS

Avarage tumor sizes were 5.64±1.85, 6.85±2.24 and 7.98±2.45 in low, medium and high SUVmax groups, respectively. The Spearman's correlation coefficient between the tumor size and SUVmax was 0.385 (p=0.004) and between the Fuhrman grade and SUVmax was 0.578 (p<0.001).

CONCLUSIONS

SUVmax appears highly correlated with tumor size and Fuhrman grade in patients with histopathologically confirmed clear cell RC. Multicenter studies are needed to provide larger series for more accurate results.

Can Initial (18)F-FDG PET-CT Imaging Give Information on Metastasis in Patients with Primary Renal Cell Carcinoma?

PURPOSE

The aim of this study was to investigate the relationship between the maximum standardized uptake values (SUVmax) of primary renal cancers with and without metastatic lesions, if any. We also studied the relationship between the size of primary renal cancers and their SUVmax, and tried to find a clinical value of (18)F-FDG PET-CT for the initial evaluation of renal cell carcinoma (RCC).

METHODS

The cases of 23 patients, 16 men and 7 women, who underwent PET-CT examination before operation were retrospectively reviewed. We measured the SUVmax of the primary renal cancers and those of any existing metastatic lesions, and the size of the primary renal cancers. We compared the SUVmax of primary RCCs with metastases and those without metastases, SUVmax of primary RCC and those of metastases, and studied the correlation between the size and SUVmax of primary RCCs.

RESULTS

The SUVmax of primary RCC of the 16 patients without metastasis ranged from 1.1 to 5.6 with a median value of 2.6. Those of the patients with metastasis ranged from 2.9 to 7.6 with a median of 5.0. The size of the all 23 primary renal cancers ranged from 1.7 cm to 13.5 cm, with a median of 4.5 cm, and their SUVmax ranged from 1.1 to 7.6, with a median of 2.9. There was a statistically significant difference between the SUVmax of the primary RCC with metastasis (5.3 ± 1.7) and those without metastasis (2.9 ± 1.0). There was a moderate positive correlation between the sizes and SUVmax of all 23 primary RCCs. However, there was no statistically significant correlation between the sizes and SUVmax of primary RCCs with metastatic lesions and the same for RCCs without metastasis. The cutoff value of SUVmax for predicting extra-renal lesion was 4.4 and that for size was 5.8 cm according to the receiver operating characteristic curves.

CONCLUSIONS

Those who have primary RCC with high SUVmax are suggested to have a likelihood of metastasis. Also, there was a moderate trend of increasing value of SUVmax of primary RCC as their size increases. Physicians should beware of missing extra-renal lesions elsewhere.

Meta-analysis of the diagnostic performance of [18F]FDG-PET and PET/CT in renal cell carcinoma

OBJECTIVES

Positron emission tomography (PET) using fluorodeoxyglucose (FDG) is useful for restaging renal cell carcinoma (RCC) and detecting metastatic diseases but is less satisfactory for detecting primary disease. We evaluated whether the integration of computed tomography (CT) scans with the PET system could increase the applicability of FDG-PET for RCC.

METHODS

The MEDLINE databases were searched for relevant studies published since 2001. Two reviewers independently assessed the methodological quality of each study identified. We then performed a meta-analysis of the sensitivity and specificity of FDG-PET findings as reported in all the selected studies.

RESULTS

Fourteen studies were eligible for inclusion. The pooled sensitivity and specificity of FDG-PET were 62% and 88% respectively, for renal lesions. For detecting extra-renal lesions, the pooled sensitivity and specificity of FDG-PET were 79% and 90%, respectively, based on the scans, and 84% and 91% based on the lesions. The use of a hybrid FDG-PET/CT to detect extra-renal lesions increased the pooled sensitivity and specificity to 91% and 88%, respectively, with good consistency.

CONCLUSIONS

For RCC, combining the FDG-PET and CT systems is helpful for detecting extra-renal metastasis rather than renal lesions. The hybrid PET/CT system has comparable sensitivity and specificity with PET in detecting extra-renal lesions of RCC.

ADVANCES IN KNOWLEDGE

The FDG-PET and PET/CT systems are both useful for detecting extra-renal metastasis in renal cell carcinoma.

Subcutaneous fatty tissue metastasis from renal cell carcinoma detected with fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography and magnetic resonance imaging

A patient who had undergone left radical nephrectomy 11 years ago for renal cell carcinoma (RCC) was referred to our clinic for restaging. Fluorine-18 fluorodeoxyglucose (F18-FDG) positron emission tomography/computed tomography (F18-FDG PET/CT) showed hypometabolic area in left frontal region of the brain and increased FDG uptake in the subcutaneous fatty tissues of the right thigh. Histopathological examination of the biopsy material from the left frontal region and right gluteal region revealed metastasis of clear cell type RCC. Seven months later, a magnetic resonance ımaging (MRI) of right cruris showed a contrast-enhancing lesion with a diameter of 3.5 cm, located at the subcutaneous area of posterior part of right cruris. A concomitant F18-FDG PET/CT detected an increased FDG uptake focus in the proximal third of right cruris adjacent to the muscle planes and this finding was consistent with metastasis of RCC.

Incidental Bilateral Renal Oncocytoma in a Patient with Metastatic Carcinoma of Unknown Primary: a Pitfall on (18)F-FDG PET/CT

Bilateral renal masses are uncommon but can raise a strong suspicion of primary or secondary malignancy, especially during the initial work-up of an oncology patient. Renal oncocytomas are benign renal tumors that are commonly discovered incidentally on diagnostic imaging with a small percentage occurring bilaterally. Although (18)F-FDG uptake in renal oncocytomas has been described, a case of a bilateral (18)F-FDG-avid renal oncocytoma has not been previously reported in the literature. A variety of malignant causes of bilateral (18)F-FDG positive renal masses are known, however it is important to include this benign etiology in the differential diagnosis. We report an unusual case of an incidental bilateral renal oncocytoma evaluated with contrast enhanced CT and (18)F-FDG PET/CT.

Squamous cell carcinoma of the right kidney on FDG PET-CT

We report the PET-CT appearance of a newly diagnosed, biopsy proven squamous cell carcinoma of the right kidney in a 61-year-old man who presented with hematuria. This is a rare tumor, with few cases reported in the literature. The patient subsequently underwent right nephrectomy shortly after the initial staging PET-CT study.

Positron emission tomography: clinical applications in oncology. Part 2

This review continues from a previous review on this topic, which was published in the December issue. In that review, the role of positron emission tomography in lung cancer, lymphoma, breast cancer, head and neck cancer, gastroesophageal cancer, colorectal cancer, malignant melanoma, bone tumors and ovarian cancer was discussed. In this review, the role of positron emission tomography in other malignancies, such as gynecological malignancies other than ovary, pancreatic cancer, hepatocellular cancer, gastrointestinal tumors, urological malignancies, neuroendocrine tumors, adrenocortical tumors, soft-tissue sarcomas, pituitary and brain tumors, is discussed.