A Concise Review of the Multimodality Imaging Features of Renal Cell Carcinoma

The evaluation of renal cell carcinoma (RCC) is routinely performed using the multimodality imaging approach, including ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). Ultrasonography is the most frequently used imaging modality for the initial diagnosis of renal masses. The modality of choice for the characterization of the renal mass is multiphasic CT. Recent advances in CT technology have led to its widespread use as a powerful tool for preoperative planning, reducing the need for catheter angiography for the evaluation of vascular invasion. CT is also the standard imaging modality for staging and follow-up. MRI serves as a problem-solving tool in selected cases of undefined renal lesions. Newer MRI techniques, such as arterial spin labeling and diffusion-weighted imaging, have the potential to characterize renal lesions without contrast media, but these techniques warrant further investigation. PET may be a useful tool for evaluating patients with suspected metastatic disease, but it has modest sensitivity in the diagnosis and staging of RCC. The newer radiotracers may increase the accuracy of PET for RCC diagnosis and staging. In summary, the main imaging modality used for the characterization, staging, and surveillance of RCC is multiphasic CT. Other imaging modalities, such as MRI and PET, are used for selected indications.

PET imaging in urology: a rapidly growing successful collaboration

PURPOSE OF REVIEW

To discuss and highlight the recent findings in urological oncology focusing on nuclear medicine advances on imaging and therapy.

RECENT FINDINGS

Testicular tumors: F-FDG as the standard positron emission tomography (PET) tracer with proven good accuracy in detecting metastatic testicular cancer; urothelial cancer: good accuracy of F-FDG PET in detecting distant metastases but poor results in detecting local disease; prostate cancer: prostate-specific membrane antigen (PSMA) is a promising target for imaging prostate cancer with unprecedented accuracy in both staging and restaging and prospective studies were recently published. In castration-resistant prostate cancer, PSMA-targeting radionuclide therapy is showing potential as a curative possibility (e.g. using Lu-PSMA); renal cell cancer (RCC): besides FDG other PET radiotracers are under clinical evaluation (e.g. antibody-based molecular imaging, metabolic radiotracers and PSMA-based tracers). PSMA-based imaging may have applications in staging clear-cell RCC and in the selection and in the antiangiogenic treatment's response assessment. Possible role of PSMA-targeting radionuclide therapy?

SUMMARY

In urological oncology, the use of F-FDG has been limited by a generally low tumor uptake and physiological F-FDG excretion by the urinary system. Other radiotracers are increasing the urologist's portfolio allowing imaging of several biochemical pathways. Theragnostic possibilities are also under investigation thanks to PSMA-based tracers.

Hypoxia, angiogenesis, and metabolism in the hereditary kidney cancers

The field of hereditary kidney cancer has begun to mature following the identification of several germline syndromes that define genetic and molecular features of this cancer. Molecular defects within these hereditary syndromes demonstrate consistent deficits in angiogenesis and metabolic signaling, largely driven by altered hypoxia signaling. The classical mutation, loss of function of the von Hippel-Lindau (VHL) tumor suppressor, provides a human pathogenesis model for critical aspects of pseudohypoxia. These features are mimicked in a less common hereditary renal tumor syndrome, known as hereditary leiomyomatosis and renal cell carcinoma. Here, we review renal tumor angiogenesis and metabolism from a HIF-centric perspective, considering alterations in the hypoxic landscape, and molecular deviations resulting from high levels of HIF family members. Mutations underlying HIF deregulation drive multifactorial aberrations in angiogenic signals and metabolism. The mechanisms by which these defects drive tumor growth are still emerging. However, the distinctive patterns of angiogenesis and glycolysis-/glutamine-dependent bioenergetics provide insight into the cellular environment of these cancers. The result is a scenario permissive for aggressive tumorigenesis especially within the proximal renal tubule. These features of tumorigenesis have been highly actionable in kidney cancer treatments, and will likely continue as central tenets of kidney cancer therapeutics.

Successful selective arterial embolizations for bone metastases in renal cell carcinoma integrated with systemic therapies: A case report

Herein is described the case of a 64-year-old patient affected by metastatic clear-cell carcinoma, with exclusive bone disease, subjected after the initial cytoreductive nephrectomy to 3 successive lines of medical treatment (sunitinib, everolimus, and sorafenib) and multiple locoregional treatments (spinal surgery, radiation therapy, and selective arterial embolization), resulting in a surprisingly long survival of over 75 months. In the era of target therapy, integration strategies, including additional locoregional treatment to medical therapy, are essential to optimize the clinical benefit, to maximize treatment duration overcoming focal progressive disease, and to improve the quality of life. In this context, we would highlight that selective transcatheter embolization of bone metastases from renal cell carcinoma should be considered as an effective and safe option in the palliative setting for patients with bone metastasis, especially for pain relief.

Metastatic renal cell carcinoma imaging evaluation in the era of anti-angiogenic therapies

During the last decade, the arsenal of anti-angiogenic (AAG) agents used to treat metastatic renal cell carcinoma (RCC) has grown and revolutionized the treatment of metastatic RCC, leading to improved overall survival compared to conventional chemotherapy and traditional immunotherapy agents. AAG agents include inhibitors of vascular endothelial growth factor receptor signaling pathways and mammalian target of rapamycin inhibitors. Both of these classes of targeted agents are considered cytostatic rather than cytotoxic, inducing tumor stabilization rather than marked tumor shrinkage. As a result, decreases in tumor size alone are often minimal and/or occur late in the course of successful AAG therapy, while tumor devascularization is a distinct feature of AAG therapy. In successful AAG therapy, tumor devascularization manifests on computed tomography images as a composite of a decrease in tumor size, a decrease in tumor attenuation, and the development of tumor necrosis. In this article, we review Response Evaluation Criteria in Solid Tumors (RECIST)-the current standard of care for tumor treatment response assessment which is based merely on changes in tumor length-and its assessment of metastatic RCC tumor response in the era of AAG therapies. We then review the features of an ideal tumor imaging biomarker for predicting metastatic RCC response to a particular AAG agent and serving as a longitudinal tumor response assessment tool. Finally, a discussion of the more recently proposed imaging response criteria and new imaging trends in metastatic RCC response assessment will be reviewed.

Positron Emission Tomography Imaging of Tumor Cell Metabolism and Application to Therapy Response Monitoring

Cancer cells do reprogram their energy metabolism to enable several functions, such as generation of biomass including membrane biosynthesis, and overcoming bioenergetic and redox stress. In this article, we review both established and evolving radioprobes developed in association with positron emission tomography (PET) to detect tumor cell metabolism and effect of treatment. Measurement of enhanced tumor cell glycolysis using 2-deoxy-2-[(18)F]fluoro-D-glucose is well established in the clinic. Analogs of choline, including [(11)C]choline and various fluorinated derivatives are being tested in several cancer types clinically with PET. In addition to these, there is an evolving array of metabolic tracers for measuring intracellular transport of glutamine and other amino acids or for measuring glycogenesis, as well as probes used as surrogates for fatty acid synthesis or precursors for fatty acid oxidation. In addition to providing us with opportunities for examining the complex regulation of reprogramed energy metabolism in living subjects, the PET methods open up opportunities for monitoring pharmacological activity of new therapies that directly or indirectly inhibit tumor cell metabolism.

Nuclear medicine in urological cancers: what is new?

ABSTRACT 

The diffusion of PET/computed tomography has opened up a new role for nuclear imaging in urological oncology. Prostate cancer is evaluated with choline (11C or 18F) PET due to a lack of sensitivity of 18F-fluorodeoxyglucose (FDG). However, many new tracers, such as 18F-fluorocyclobutane-1-carboxylic acid and 68Ga-prostate-specific membrane antigen, are under investigation, offering promising results in the particular setting of radically treated patients with biochemical relapse. The performance of 18F-FDG depends on the histological type; indeed, renal cell cancer may present variable metabolic uptake. In this field, mainly antibodies labeled with positron emitters are under clinical evaluation. Finally, 18F-FDG PET/computed tomography has been proven to show good accuracy in detecting metastatic testicular and bladder cancers, despite not having valid results in detecting local disease. The urological cancer diagnostic process is currently under continuous development.

Imaging in renal cell carcinoma

Imaging plays a central role in the detection, diagnosis, staging, and follow-up of renal cell carcinoma (RCC). Most renal masses are incidentally detected with modern, high-resolution imaging techniques and a variety of management options exist for the renal masses encountered today. This article discusses the role of multiple imaging modalities in the diagnosis of RCC and the imaging features of specific pathologic subtypes and staging techniques. Future directions in RCC imaging are presented, including dynamic contrast-enhanced and unenhanced techniques, as well as the development of novel tracers for positron emission tomography.

Gas challenge-blood oxygen level-dependent (GC-BOLD) MRI in the rat Novikoff hepatoma model

PURPOSE

The purpose of the study was to investigate the relationship between gas challenge-blood oxygen level-dependent (GC-BOLD) response angiogenesis and tumor size in rat Novikoff hepatoma model.

MATERIALS AND METHODS

Twenty adult male Sprague-Dawley rats (weighting 301-325 g) were used for our Animal Care and Use Committee-approved experiments. N1-S1 Novikoff hepatomas were grown in 14 rats with sizes ranging from 0.42 to 2.81 cm. All experiments were performed at 3.0 T using a custom-built rodent receiver coil. A multiple gradient-echo sequence was used for R2* measurements, first during room air (78% N(2)/20% O(2)) breathing and then after 10 min of carbogen (95% O(2)/5% CO(2)) breathing. After image acquisition, rats were euthanized, and the tumors were harvested for histological evaluation.

RESULTS

The R2* change between air and carbogen breathing for small hepatomas was positive; R2* changes changed to negative values for larger hepatomas. We found a significant positive correlation between tumor R2* change and tumor microvessel density (MVD) (r=0.798, P=.001) and a significant inverse correlation between tumor R2* change and tumor size (r=-0.840, P<.0001).

CONCLUSIONS

GC-BOLD magnetic resonance imaging measurements are well correlated to MVD levels and tumor size in the N1-S1 Novikoff hepatoma model; GC-BOLD measurements may serve as noninvasive biomarkers for evaluating angiogenesis and disease progression and/or therapy response.

Assessment of Therapeutic Effect of Sunitinib by (11)C-Acetate PET Compared with FDG PET Imaging in a Patient with Metastatic Renal Cell Carcinoma

Although sunitinib shows a high response rate in patients with untreated metastatic renal cell carcinoma (mRCC), quite a few patients show no therapeutic effect. Therefore, it is crucial to distinguish the patients who respond to sunitinib from those who do not as early as possible after the administration of the therapy. We herein report a case of mRCC in which (11)C-acetate (AC) positron emission tomography (PET) showed an early therapeutic effect of sunitinib treatment 4 weeks after its administration.

Automated production of [11C]acetate and [11C]palmitate using a modified GE Tracerlab FX(C-Pro)

As researchers explore new applications for positron emission tomography radiopharmaceuticals, the demand for effective and readily available radiopharmaceuticals continues to increase. The syntheses of two such radiopharmaceuticals, [(11)C]acetate and [(11)C]palmitate, can be automated on the GE Tracerlab FX(C-Pro) by utilizing Grignard reactions. Radiochemical purities of the [(11)C]acetate and the [(11)C]palmitate products were high (>98% and >99.9%, respectively) with average non-corrected yields of 18% (n = 3) and 10% (n = 5), respectively. These data comprise the validation trials for site qualification of clinical production of both radiopharmaceuticals.

Metastatic Paraganglioma and Treatment with Sunitinib: A Case Report

Sunitinib malate is a small kinase inhibitor with activity against a number of tyrosine kinase receptors. We treated a young man suffering from a metastatic paraganglioma with sunitinib. In this report we discuss a number of related questions including the correct dosage, schedules and timing of administration of the molecule, the main side effects and their treatment, and evaluation of the treatment response by CT scan.

Treatment with sunitinib started at a dose of 50 mg daily for 4 weeks followed by 2 weeks off (4/2). Because of the side effects, the dose was reduced to 25 mg daily (4/2) and then to 25 mg daily (2/1). This resulted in a significant decrease in the plasma chromogranin A value and the radiological size of the metastases, as well as important clinical improvement. After 6 cycles the treatment was stopped because of a rise in plasma NSE values and disease progression. Sunitinib malate can induce marked toxicity, in which case the daily dose should be reduced and a different schedule of administration adopted. Response evaluation by CT scan should take into account tumor necrosis caused by sunitinib. Sunitinib malate is an interesting molecule for targeted therapy also for advanced neuroendocrine tumors. There has been evidence of significant clinical improvement, as in the case reported here. Free full text available at www.tumorionline.it

Functional imaging of renal cell carcinoma

The incidence of early and advanced-stage renal cell carcinoma (RCC) is increasing. Methods of diagnosing, staging and evaluating tumor burden that are more accurate and reliable than the currently available options are needed in order to identify RCC at a stage at which it is curable and to accurately determine the response to treatment. Functional imaging, particularly with combined PET-CT, might improve accuracy of detection and provide essential information that has been unavailable to date. This approach is against a background in which targeted therapies for metastatic RCC have entered clinical practice in the past few years, further highlighting the importance of accurate imaging for patient selection and for monitoring response to treatment. We outline the current clinical status of functional imaging in RCC using PET-CT, which allows simultaneous capture and co-registration of functional and anatomical data. New radiotracers and approaches-including radiolabeled monoclonal antibodies and imaging of tumor hypoxia-are touched on, and areas of future research discussed.

Targeted therapies in renal cell cancer: recent developments in imaging

Targeted therapy has significantly improved the perspectives of patients with metastatic renal cell cancer (mRCC). Frequently, these new molecules cause disease stabilization rather than substantial tumor regression. As treatment options expand with the growing number of targeted agents, there is an increasing need for surrogate markers to early assess tumor response. Here, we review the currently available imaging techniques and response evaluation criteria for the assessment of tumor response in mRCC patients. For computed tomography (CT), different criteria are discussed including the Response Evaluation Criteria in Solid Tumors (RECIST), the Choi criteria, the modified Choi criteria, and the size and attenuation CT (SACT) criteria. Functional imaging modalities are discussed, such as dynamic contrast-enhanced CT (DCE-CT), dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), dynamic contrast-enhanced ultrasonography (DCE-US), and positron emission tomography (PET).

Initial experience with 18F-fluoroethylcholine PET/CT in staging and monitoring therapy response of advanced renal cell carcinoma

OBJECTIVE

The use of 18F-fluoroethylcholine (FEC) PET/ CT in staging and monitoring therapy response of advanced renal cell carcinoma (RCC) was prospectively analysed.

METHODS

Preliminary results of two patients with metastatic RCC who underwent tumour nephrectomy as well as FEC PET/CT before and 10 weeks after two cycles of tyrosine kinase inhibitor therapy are presented.

RESULTS

All in all, 18 tumour lesions were detected by baseline PET/CT, of which 10 (56%) were positive in FEC PET and 17 (94%) visible on contrast-enhanced computed tomography (ceCT). Mainly, small lung metastases resulted in the lower detection rate of FEC PET compared with ceCT. In follow-up PET/CT of the first case, progressive disease (PD) occurred with increase in tumour diameters of all metastases but non-uniform metabolic response. In the second case, partial response (PR) was achieved with concordant results of PET and CT. These results were confirmed by further CT in the course of disease.

CONCLUSIONS

In this small sample more than half of the RCC metastases were evident in baseline FEC PET. Monitoring therapy, FEC PET showed heterogeneous results in the first case with PD and was consistent with ceCT in the second one displaying PR.