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

Primary Small Cell Carcinoma of the Kidney: A Case Study with Emphasis on Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography Findings

Small cell carcinoma (SCC) of the kidney is included in extrapulmonary SCC which is a group of extremely rare but highly aggressive cancers. There have been only a few case reports and small retrospective series in the literature describing the malignancy in kidneys. Most of the published reports describe the entity as a variant mixed with other tumor subtypes such as urothelial carcinoma, adenocarcinoma, and squamous cell carcinoma. Pure-form SCC in kidneys is exceedingly rare. Fluorodeoxyglucose positron emission tomography-computed tomography plays an essential role in the accurate staging evaluation of this cancer.

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.

Efficacy of Pre-operative 18F-FDG PET/CT in Prognostic Prediction in Patients With Renal Cell Carcinoma

BACKGROUND/AIM

This study analyzed the parameters provided by preoperative ¹⁸ F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) for prognostic prediction of renal cell carcinoma (RCC).

PATIENTS AND METHODS

FDG-PET/CT data from 66 clear cell RCC and 19 non-clear cell RCC cases between January 2015 and October 2018 were reviewed retrospectively. We compared the two groups according to recurrence/metastasis to determine prognosis-influencing factors. Multivariate Cox hazard regression models were constructed to evaluate factors potentially predicting disease-free survival (DFS) after adjustment for confounders. DFS was then compared between groups.

RESULTS

Standardized uptake values (SUV) of the PET/CT scan were independent predictors of prognosis after adjusting for confounders. RCC cases were divided into two groups by optimal cut-off values. Differences between DFS percentages in high and low SUV groups were significant. Similar results were obtained in clear cell RCC groups.

CONCLUSION

Increased SUV of the PET/CT scan are significant predictors of worse prognoses in patients with surgically resected RCC.

The role of dual tracer PSMA and FDG PET/CT in renal cell carcinoma (RCC) compared to conventional imaging: A multi-institutional case series with intra-individual comparison

PURPOSE

The objective of this study was to perform an intra-individual dual tracer comparison of Fluorodeoxyglucose (FDG) and Prostate Specific Membrane Antigen (PSMA) computed tomography (CT)/Positron Emission Tomography (PET) against standard of care (SOC) imaging for the characterisation, staging and restaging of renal cell carcinoma (RCC).

METHODS

A multicentre retrospective cohort study was performed at 3 major tertiary referral institutions in Brisbane, Australia between 2015 and 2020. All patients who underwent both PSMA and FDG PET/CT following SOC imaging for investigation of RCC were identified. Clinical details, imaging characteristics and histopathology were collected prior to univariate statistical analysis.

RESULTS

Eleven patients who underwent dual tracer PET/CT were included. Mean age was 65.5 years (SD 8.8). Most patients were male (64%) with clear cell morphology (91%). The indication for dual tracer PET was staging (36%) and restaging after radical/partial nephrectomy (64%). Primary tumour assessment showed mixed avidity patterns (concordant 40%, discordant favouring PSMA 20%, and FDG 40%). Metastatic disease assessment showed concordant avidity in 6 patients (55%), concordant negative in 3 (27%), and discordant uptake favouring PSMA. PET outperformed SOC imaging for assessment of metastatic disease in 5 patients (45%) and equivalent for the remainder. A change in management was noted in three cases (27%).

CONCLUSION

Dual tracer FDG and PSMA PET/CT for assessment of primary and metastatic RCC were mostly concordant. PET imaging outperformed conventional imaging and led to a change in management for 1 in 4 patients. Further studies with larger samples sizes are required to validate these findings and identify characteristics to guide patient selection for selective or dual tracer use.

[Imaging of oligometastatic disease in selected urologic cancers]

BACKGROUND

Local treatment of the primary or metastatic sites in urologic malignancies is promising when compared to systemic therapy alone, leading to the definition of a potentially curative oligometastatic state.

OBJECTIVES

Comparison of imaging modalities regarding local and metastatic tumor sites in urologic cancers.

METHODS

Review of comparative trials addressing quality criteria of imaging modalities.

RESULTS

Depending on primary tumor and metastatic site, conventional imaging modalities such as computer tomography (CT) and bone scintigraphy still represent the standard of care in Germany. Due to superior quality criteria, hybrid-imaging techniques were widely adopted for oncological staging and particular due to the new PSMA-ligand (PSMA-PET/CT) in prostate cancer imaging. The development of new radioisotopes as well as their clinical application remains a focus of current research.

CONCLUSIONS

High-quality diagnostic imaging modalities lay the groundwork for a precise definition of an oligometastatic state. By enabling treatment of the entire tumor burden, a delay of systemic therapy, longer progression-free survival, or even curative treatment may become achievable.

PET/CT limitations and pitfalls in urogenital cancers

Hybrid FDG PET/CT plays a vital role in oncologic imaging and has been widely adopted for the staging and restaging of a variety of malignancies. Its diagnostic value in urogenital malignancies is less well-known, not at least because of the variable FDG avidity of these tumor entities, the sites of these tumors, and technical challenges associated with sequential imaging of CT and PET. PET/CT interpretation thus can be especially challenging and is associated with many pitfalls, which can lead to both false-positive and false-negative diagnoses as well as incorrect assessment of metabolic change following therapy. Currently, FDG PET/CT is not the standard of care for the initial diagnosis or staging of early-stage or low-risk urogenital cancers; however, it can help evaluate distant metastatic disease, response to therapy, and disease recurrence in high-risk patients. Knowledge of imaging features of tumor metabolic avidity and pitfalls is essential for accurate interpretation.

18Fluorodeoxyglucose-positron emission tomography/computed tomography for differentiation of renal tumors in hereditary kidney cancer syndromes

PURPOSE

To assess differences in FDG-PET/CT uptake among four subtypes of renal tumors: clear cell RCC (ccRCC), papillary type I and II RCC (pRCC), and oncocytoma.

METHODS

This retrospective study investigated 33 patients with 98 hereditary renal tumors. Lesions greater than 1 cm and patients with a timeframe of less than 18 months between preoperative imaging and surgery were considered. FDG-PET/CT images were independently reviewed by two nuclear medicine physicians, blinded to clinical information. Volumetric lesion SUV_mean was measured and used to calculate a target-to-background ratio respective to liver (TBR). The Shrout-Fleiss intra-class correlation coefficient was used to assess reliability between readers. A linear mixed effects model, accounting for within-patient correlations, was used to compare TBR values of primary renal lesions with and without distant metastasis.

RESULTS

The time interval between imaging and surgery for all tumors had a median of 77 (Mean: 139; Range: 1-512) days. Intra-class reliability of mean TBR resulted in a mean κ score of 0.93, indicating strong agreement between the readers. The mixed model showed a significant difference in mean TBR among the subtypes (p < 0.0001). Pairwise comparison showed significant differences between pRCC type II and ccRCC (p < 0.0001), pRCC type II and pRCC type I (p = 0.0001), and pRCC type II and oncocytoma (p = 0.0016). Furthermore, a significant difference in FDG uptake was present between primary pRCC type II renal lesions with and without distant metastasis (p = 0.023).

CONCLUSION

pRCC type II lesions demonstrated significantly higher FDG activity than ccRCC, pRCC type I, or oncocytoma. These findings indicate that FDG may prove useful in studying the metabolic activity of renal neoplasms, identifying lesions of highest clinical concern, and ultimately optimizing active surveillance, and personalizing management plans.

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.

Impact of PET/CT for Assessing Response to Immunotherapy-A Clinical Perspective

Cancer immunotherapy using immune-checkpoint inhibitors (ICI) has revolutionized the therapeutic landscape of various malignancies like non-small-cell lung cancer or melanoma. Pre-therapy response prediction and assessment during ICI treatment is challenging due to the lack of reliable biomarkers and the possibility of atypical radiological response patterns. Positron emission tomography/computed tomography (PET/CT) enables the visualization and quantification of metabolic lesion activity additional to conventional CT imaging. Various biomarkers derived from PET/CT have been reported as predictors for response to ICI and may aid to overcome the challenges clinicians currently face in the management of ICI-treated patients. In this narrative review, experts in nuclear medicine, thoracic oncology, dermatooncology, hemato- and internal oncology, urological and head/neck tumors performed literature reviews in their respective field and a joint discussion on the use of PET/CT in the context of ICI treatment. The aims were to give a clinical overview on present standards and evidence, to identify current challenges and fields of research and to enable an outlook to future developments and their possible implications. Multiple promising studies concerning ICI response assessment or prediction using biomarkers derived from PET/CT alone or as composite biomarkers have been identified for various malignancies and disease stages. Of interest, additional major incentives in the field may evolve from novel tracers specifically targeting immune-checkpoint molecules which could allow not only response assessment and prognosis, but also visualization of histological tumor cell properties like programmed death-ligand (PD-L1) expression in vivo. Despite the broad range of existing literature on PET/CT-derived biomarkers in ICI therapy, implications for daily clinical practice remain elusive. High-quality prospective data are urgently warranted to determine whether patients benefit from the application of PET/CT in terms of prognosis. At the moment, the lack of such evidence as well as the absence of standardized imaging methods and biomarkers still precludes PET/CT imaging to be included in the relevant clinical practice guidelines.

Renal Cell Carcinoma Ablation: Preprocedural, Intraprocedural, and Postprocedural Imaging

The rising incidence of renal cell carcinoma (RCC) in recent decades necessitates careful consideration of additional treatment options, especially for patients who may be poor surgical candidates. An emerging body of evidence suggests that ablation may be performed effectively and safely even in patients with multiple comorbidities. Accordingly, clinical guidelines now include thermal ablation as an alternative for such patients with localized tumors that are 4.0 cm or smaller. Recent experience with these minimally invasive techniques has led to a greater understanding of the imaging findings that merit close attention when ablation is anticipated, or after it is performed. These imaging findings may guide the interventionalist's perception of the risks, technical challenges, and likelihood of treatment success associated with RCC ablation. The present review provides an overview of clinically relevant radiologic findings during the preprocedural, intraprocedural, and postprocedural period in the context of image-guided renal ablation. Keywords: Interventional-Body, Kidney, Percutaneous, Urinary © RSNA, 2019.

PET-CT and PET-MR in urological cancers other than prostate cancer: An update on state of the art

Hybrid positron emission tomography with computed tomography (PET/CT) and magnetic resonance imaging (PET/MRI) have enabled the combination of morphologic and functional imaging with the promise of providing better information in guiding therapy. Further advance has been made in the past decade with the development of newer radiotracers and optimization of the technical aspects. We performed a search in PubMed, Scopus, and Google Scholar for peer-reviewed literature concerning the advances and newer developments in the imaging of nonprostate urologic cancers between 2005 and 2017. This review aims at summarizing the current evidence on PET imaging in nonprostate urologic cancers and their impact on the diagnosis, staging, prognostication, response assessment, and restaging of these malignancies. However, much of the evidence is still in infancy and has not been incorporated into routine management or the practice guidelines of National Comprehensive Cancer Network or European Society for Medical Oncology (ESMO).

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.

Diagnostic Challenges of Kidney Cancer: A Systematic Review of the Role of Positron Emission Tomography-Computerized Tomography

PURPOSE

Positron emission tomography-computerized tomography is a leading imaging modality for many types of solid tumors. The ability to characterize molecular processes noninvasively during a relatively fast whole-body scan is the major advantage of this technology. We reviewed the literature in an attempt to clarify the usefulness of positron emission tomography-computerized tomography in patients with a renal mass.

MATERIALS AND METHODS

We searched PubMed® for articles published from 2004 through September 2015 using the keywords "renal," "kidney," "mass," "tumor," "cancer," and "PET/CT."

RESULTS

A total of 158 relevant articles were included in the review. Most diagnostic studies used (18)F-fluorodeoxyglucose, a marker of glucose metabolism, as the radiotracer. The results were substandard, with sensitivity rates in the range of 31.5% to 77% for diagnosis of renal cell carcinomas. There were higher success rates for diagnosis of clear cell carcinomas. Carbonic anhydrase IX is an enzyme expressed in 95% of clear cell carcinomas but not in normal renal tissue or in benign or nonclear cell malignancies. A chimeric mouse-human antibody to carbonic anhydrase IX labeled with (124)I-girentuximab was demonstrated to diagnose clear cell tumors with sensitivity of 86.2% and specificity of 85.9%. For diagnosis of metastases positron emission tomography-computerized tomography with (18)F-fluorodeoxyglucose was observed to be more accurate than computerized tomography alone (94% vs 89%). Studies with other tracers also reveal encouraging results. Positron emission tomography-computerized tomography holds great promise in predicting prognosis and response to tyrosine kinase inhibitors. Current tyrosine kinase inhibitor treatments usually induce only mild lesion shrinkage. Thus, assessment of response based on changes in size of metastases is insufficient. Low (18)F-fluorodeoxyglucose uptake before treatment and decreased uptake after 2 cycles of treatment are associated with better survival. Using labeled medications as radiotracers before actual treatment may assist in selection of the most effective medication for a specific patient.

CONCLUSIONS

Positron emission tomography-computerized tomography with (18)F-fluorodeoxyglucose currently has lower sensitivity compared to enhanced computerized tomography for diagnosis of primary renal masses but better sensitivity for diagnosis of metastases. Predicting and monitoring response to targeted therapy could direct the clinician toward drug selection or modification during therapy. The possibility of treating patients with advanced renal cell carcinoma with (124)I-girentuximab attached to (177)Lu, a strong β-emitter, is investigated.

Imaging of renal cell carcinoma

Renal cell carcinoma (RCC) is the most common kidney cancer in adults. Early and accurate imaging plays an important role in the detection, staging, and follow-up of RCC. Patient care and case management revolves heavily around diagnostic imaging so it is imperative that appropriate and adequate imaging is acquired. There are well-established standard imaging protocols available to patients and their providers, although at the same time, there is also extensive ongoing research on improving the various modalities. Ultrasound has been the most commonly used imaging technique for renal imaging in general. However, computed tomography (CT) is the first choice for imaging of renal masses, and has been the mainstay for several decades. High resolution, reproducibility, reasonable preparation and acquisition time, and acceptable cost allow CT to remain as the primary choice for radiologic imaging. Magnetic resonance imaging (MRI) is considered as an important alternative in patients requiring further imaging or in cases of allergies, pregnancy, or surveillance. With increasing concern over radiation exposure, there has been a trend toward the higher use of MRI. It is important to understand the various imaging options available, as well as the current status of and results from recent RCC imaging studies. In this review we discuss these modalities, including the current state of ultrasound, CT, and MRI in RCC.