A Review of Prostate-Specific Membrane Antigen (PSMA) Positron Emission Tomography (PET) in Renal Cell Carcinoma (RCC)

Metastatic renal cell carcinoma (mRCC) is a disease that portends poor prognosis despite an increasing number of novel systemic treatment options including new targeted therapies and immunotherapy. Ablative intervention directed at oligometastatic RCC has demonstrated survival benefit. Consequently, developing techniques for improved staging of mRCC on contemporary imaging modalities including X-ray computed tomography (CT), magnetic resonance imaging (MRI) and/or bone scan (BS) is a clinical priority. This is relevant for metastatic deposits too small to characterize or lymph nodes within physiological normality. Prostate-specific membrane antigen (PSMA) is a type II transmembrane glycoprotein highly expressed on prostate cancer epithelial cells. Recently, small molecules targeting the PSMA receptor, linked to radioactive isotopes have been developed for use with positron emission tomography (PET). Despite its nomenclature, PSMA has also been found to be expressed in the neovasculature of non-prostate cancers such as renal cell carcinoma (RCC) and hence PSMA PET/CT imaging has been proposed as an alternative staging modality. Preliminary small studies involving the use of PSMA PET/CT imaging in mRCC have been encouraging with evidence of improved staging sensitivity which has directly led to change in management in some cases. Given these early encouraging reports, we performed a comprehensive narrative review on the available evidence, including the scientific basis for PSMA expression in RCC, the role of PSMA PET/CT imaging with potential clinical implications in mRCC, its limitations and future opportunities.

A large bi-lobed classic renal angiomyolipoma with vena caval extension

Renal angiomyolipomas (AMLs) are the most common benign renal tumors encountered, and composed of 3 components: mature adipose tissues, smooth muscles, and blood vessels. Mostly asymptomatic and discovered incidentally, the classic type of AMLs rarely extend to involve great vessels. Radiological confirmation of such lesions is paramount for diagnosis and planned intervention. Management of AMLs is based on clinical presentation and varies from active surveillance to invasive surgical interventions. A case of sizeable classic AML with extension to inferior vena cava is presented here, with successful tumor resection performed after complete liver mobilization. A literature review and a summary of similar cases are also presented. A multidisciplinary approach is required for proper and precise radiological diagnosis to achieve an adequate surgical resection, which might sometimes be complicated and complex, as in this current case.

Usefulness of PET/CT 18-FDG for the diagnosis and follow-up of urological, urothelial and kidney tumours

INTRODUCTION

New imaging studies have appeared in recent years for the diagnosis and follow-up of metastatic urological tumours.

MATERIAL AND METHODS

A total of 41 patients were reviewed with suspected recurrence of a urothelial or kidney tumour, analysing the diagnostic performance of PET-CT scans undertaken between 2013 and 2016.

RESULTS

We collected 17 urothelial tumours and 24 renal tumours, with a median follow-up of 30 months. A total of 39.3% of the urothelial tumours were high grade and 29.3% of the kidney tumours were clear cell Fuhrman II. As a whole, the imaging studies detected recurrences in 34 patients. CT was positive in 83% of the patients, while the PET scan was positive in 75.6%, CT/PET coincidence was 50%. The PET scan detected further disease in 41% of the cases compared to 5% by CT. This resulted in a change of therapeutic strategy in 40% of the patients. Sensitivity, specificity, positive predictive value and negative predictive value for the CT and the PET scans were 92% and 92%, 57% and 100%, 92% and 100%, and 57% and 70% respectively.

CONCLUSION

The PET scan showed similar sensitivity for urological tumours to the standard imaging techniques but with higher specificity, positive predictive value and negative predictive value. This led to a change in treatment strategy for 40% of the patients in our series. The PET scan will probably become the standard test in the extension and follow-up studies of most urological tumours.

Role of contrast-enhanced 18F-FDG PET/CT imaging in the diagnosis and staging of renal tumors

PURPOSE

The objectives of this prospective study are to compare intravenous contrast-enhanced (CE) fluorine-18-fluorodeoxyglucose (F-FDG) PET/computed tomography (CE F-FDG PET/CT) with conventional methods (CT/MRI) and to evaluate the relationship of maximum standardized uptake value (SUVmax) with Fuhrman grade in patients with renal tumors.

PATIENTS AND METHODS

A total of 62 patients [35 males and 27 females; mean age 55.8±12.7 (range: 27-81) years] were enrolled in the study. CE F-FDG PET/CT scanning included whole-body (early) and abdominal imaging (late) 1 and 2 h after intravenous F-FDG administration, respectively. SUVmax was calculated for primary tumors. CE F-FDG PET/CT and CT/MRI findings were compared with respect to primary tumors and staging.

RESULTS

The sensitivity of CE F-FDG PET/CT in primary tumor detection was 98%, which was very close to that of CT/MRI (100%). CE F-FDG PET/CT resulted in correct staging in 84% of the cases, compared with 68% of the cases with conventional methods (52 vs. 42 patients). SUVmax values of early PET for the primary tumors were significantly correlated with the Fuhrman grades (P<0.001). CE F-FDG PET/CT enabled the detection of synchronous tumors in four patients, one of which was incorrectly diagnosed as having metastasis by CT. Distant metastases were detected in 16 patients with CE F-FDG PET/CT and in 13 patients with routine conventional methods.

CONCLUSION

CE F-FDG PET/CT showed similar results compared with CT/MRI in the detection of primary tumors, but it was superior to conventional methods in the detection of metastasis and staging. Given the highly significant correlation between SUVmax values and the Fuhrman grading, CE F-FDG PET/CT may play a significant role in the evaluation of patient prognosis.

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 ¹⁸F-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.

FDG PET or PET/CT in evaluation of renal angiomyolipoma

Objective

Angiomyolipoma is the most common benign kidney tumor. However, literature describing FDG PET findings on renal angiomyolipoma (AML) is limited. This study reports the FDG PET and PET/CT findings of 21 cases of renal AML.

Materials and Methods

The study reviews FDG PET and PET/CT images of 21 patients diagnosed with renal AML. The diagnosis is based on the classical appearance of an AML on CT scan with active surveillance for 6 months. The study is focused on the observation of clinical and radiographic features.

Results

Six men and 15 women were included in our study. The mean age of the patients was 57.14 ± 9.67 years old. The mean diameter of 21 renal AML on CT scans was 1.76 ± 1.00 cm (Min: 0.6 cm; Max: 4.4 cm). CT scans illustrated renal masses typical of AMLs, and the corresponding FDG PET scans showed minimal FDG activities in the area of the tumors. None of the 21 AMLs showed a maximum standardized uptake value (SUV_max) greater than 1.98. No statistically significant correlation was present between SUV_max and tumor size.

Conclusion

Renal AMLs demonstrate very low to low uptake on FDG PET and PET/CT imaging in this study. When a fat-containing tumor in the kidney is found on a CT scan, it is critical to differentiate an AML from a malignant tumor including an RCC, liposarcoma, and Wilms tumor. This study suggests that FDG PET or PET/CT imaging is useful for differentiating a renal AML from a fat-containing malignant tumor.

18F-FDG PET/CT in the characterization and surgical decision concerning adrenal masses: a prospective multicentre evaluation

PURPOSE

This prospective multicentre study assesses the usefulness of FDG PET/CT in characterizing and making the therapeutic decision concerning adrenal tumours that are suspicious or indeterminate in nature after conventional examinations (CE).

METHODS

Seventy-eight patients (37 men, 41 women, 81 adrenal lesions) underwent FDG PET/CT after CE including CT scan, biological tests and optionally (131)I-metaiodobenzylguanidine (MIBG) and/or (131)I-norcholesterol scans. FDG adrenal uptake exceeding that of the liver was considered positive. PET results were not decisive. Surgery was discussed when at least one of the following criteria was found during CE: size >3 cm, spontaneous attenuation value >10 HU, heterogeneous aspect, abnormal MIBG or norcholesterol scan or hormonal hypersecretion.

RESULTS

Following the gold standard (histology analysis or >or=9 months follow-up), 49 lesions potentially qualified for surgery (malignant = 27, benign secreting = 22) and 32 benign non-secreting lesions did not. PET was negative in 97% of non-surgical lesions and positive in 73% of potentially surgical ones which included all the malignant lesions, except 3 renal cell metastases, and 12 of 22 benign secreting lesions. The negative predictive value for malignancy was 93% (41/44) and positive predictive value for detecting surgical lesions was 97% (36/37). A high FDG uptake (maximum standardized uptake value >or= 10) was highly predictive of malignancy.

CONCLUSION

Adrenal FDG uptake is a good indicator of malignancy and/or of secreting lesions and should lead one to discuss surgery. If there is no prior history of poorly FDG-avid cancer, the absence of FDG uptake should avoid unnecessary removal of benign adrenal lesions.

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.

18F-FDG PET/CT imaging for an early assessment of response to sunitinib in metastatic renal carcinoma: preliminary study

PURPOSE

Sunitinib is a new standard for the treatment of metastatic renal-cell carcinoma (RCC). We evaluated the accuracy of 18-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) in assessing early response to this antiangiogenic drug, which cannot be obtained with conventional CT.

PROCEDURES

Patients had an FDG-PET/CT at baseline and another one for follow-up at the end of the first cycle (at day 42). For each examination, all lesions were registered and the maximum standardized uptake value (SUV(max)) was measured. The metabolic response on PET at day 42 was assessed, using European Organization for Research and Treatment of Cancer criteria. Morphologic response on CT at day 84 (after two cycles), using Response Evaluation Criteria in Solid Tumors criteria, was used as the reference standard. The long-term outcome was assessed by the progression-free survival.

RESULTS

Twelve (12) patients who completed at least two cycles of sunitinib were assessed. The SUV(max) for the lesions with the highest uptake ranged between 2.9 and 11.8 for the 12 patients (mean = 6.3). Early PET/CT findings, after one cycle of sunitinib, were consistent with later CT results in 9 patients of 11 assessable patients: 1 patient progressed on PET and CT, 7 patients had stable disease, and 1 had a partial response. The other 2 patients had a metabolic partial response on PET and stable disease on CT. However, 1 patient achieved a partial response later in follow-up, suggesting that metabolic early changes are an indication of sunitinib activity.

CONCLUSION

FDG-PET/CT seems to be an interesting tool for the early evaluation of response to sunitinib in metastatic RCC. Larger studies are needed to confirm these preliminary results and establish a prognostic value for PET/CT.