Positron emission tomography (PET) in the urooncological evaluation of the small pelvis

Positron emission tomography (PET) with the use of (¹⁸F)2-fluoro-d-2-desoxyglucose (FDG) has been investigated to be a highly sensitive and specific imaging modality in the diagnostic of primary and recurrent tumors and in the control of therapies in numerous non-urologic cancers. The aim of this review is to validate the significance of PET as a diagnostic tool in malignant urological tumors of the small pelvis. A systematic review of the current literature concerning the role of PET for malignant prostate, testicular and bladder tumors was carried out. The data indicate no additional role for PET in comparison with conventional imaging in tumor detection and local staging for prostate, bladder or testicular cancer. Tumor recurrence in prostate cancer seems to be more effectively identified with acetate and choline than with FDG, but this effect is more pronounced with higher PSA values. The value of PET in the identification of metastatic disease in either tumor entity can not be finally outlined as the clinical data are partly missing, controversial or in the process of evaluation. FDG-PET can be regarded as accepted imaging modality in the restaging of seminomatous germ cell tumors after chemotherapy.     

The clinical advances of fluorine‐2‐D‐deoxyglucose – positron emission tomography/computed tomography in urological cancers

Fluorine‐18 labeled fluorine‐2‐D‐deoxyglucose (FDG) is the most frequently used positron emission tomography (PET) probe but it has certain limitations when used in urological cancers. The introduction of co‐registered PET and computed tomography (PET/CT) represents a major advance in technology and FDG‐PET/CT has now become the new standard. The diagnostic performance of FDG‐PET and PET/CT depends on the metabolic activity of tumor tissue, which is generally low in primary renal cell and prostate cancers and often in their metastatic deposits. In contrast, both seminomatous and nonseminomatous germ cell tumors are characterized by upregulated glucose metabolism with subsequently increased FDG uptake in tumor sites. Generally, the metabolic activity provides accurate information regarding the presence of a viable tumor, except in patients with residual mature teratoma. Although bladder cancer demonstrates sufficiently increased FDG uptake, primary tumors are difficult to identify due to the renal excretion of FDG. The accuracy of FDG‐PET/CT in metabolically active metastases is generally higher compared to conventional CT except for identifying small lung deposits. With disease progression and subsequent de‐differentiation of prostate cancer, castrate resistant disease is more likely to present with lesions that have increased glucose metabolism.     

Diagnosis and monitoring of urological tumors using positron emission tomography.

The purpose of this article was to critically review the diagnostic value of positron emission tomography (PET) in urological oncology. Urinary tract tumor assessment is hampered by the renal elimination of (18)F-fluorodeoxyglucose (FDG), the most commonly used PET radiopharmaceutical. PET imaging offers no significant benefits over conventional imaging modalities for renal cell and bladder carcinomas. As a result of the low metabolic activity of prostate cancer, PET does not differentiate adequately between adenoma and carcinoma, nor detect local recurrence after radical prostatectomy with sufficient sensitivity. However, lymph node staging with FDG-PET, specifically in bladder cancer, has been shown to have a potential clinical benefit. Further studies are required to determine the clinical value of retroperitoneal lymph node staging and recurrent disease detection in germ cell tumors. Finally, encouraging early results exist for the use of serial PET measurements to predict and assess therapy response to chemotherapy which may also be valuable in urological oncology.     

Molecular positron emission tomography and PET/CT imaging in urological malignancies

OBJECTIVES: Positron emission tomography (PET) provides unique insights into molecular pathways of diseases. PET using [F-18]-fluorodeoxyglucose (FDG) has gained increasing acceptance for the diagnosis, staging, and treatment monitoring of various tumour types. The aim of this review is to provide an update on the current status of molecular PET and PET/CT imaging in urological malignancies. METHODS: The current literature on PET and PET/CT imaging was reviewed and summarized for prostate cancer, bladder cancer, renal cell carcinoma, and germ cell tumours. RESULTS: Depending on the radiotracer used, PET offers diagnostic information based on glucose, choline or amino acid metabolism and has also been applied to imaging tumour cell proliferation and tissue hypoxia in urological malignancies. The diagnostic performance of FDG-PET is hampered by the renal excretion of FDG and by the low metabolic activity often seen in tumours such as prostate cancer. However, new PET tracers including radiolabelled choline and acetate may offer an alternative approach. There is consistent evidence that FDG-PET provides important diagnostic information in detecting metastatic and recurrent germ cell tumours and it might offer additional information in the staging and restaging of bladder and renal cancer. CONCLUSIONS: Although PET imaging has been shown to be a clinically useful tool, its application in urological malignancies still needs to be fully determined by larger prospective trials. The introduction of novel PET radiopharmaceuticals along with the new technology of PET/CT will likely change the future role of molecular imaging in urological malignancies.     

Detection of unknown primary tumor in a patient with cerebellar metastasis using FDG PET-CT: case report

Identification of unknown primary tumors in patients with brain metastasis is a continued diagnostic challenge. Several clinical reports have suggested that 18F-flouorodeoxyglucose positron emission tomography (FDG PET) is useful for detecting them. PET has incomparable abilities to determine the metabolic activity of tissues. But it needs the assistance of higher-resolution, anatomic information. CT is the easiest and highest-resolution tomographic modality to be integrated into PET imaging. Because of this, the market for PET devices has shifted so dramatically toward PET-CT. We report a case to show that FDG PET-CT was able to detect an unknown primary tumor. A 75-year-old female underwent resection of a left cerebellar tumor. The histological diagnosis was adenocarcinoma metastasis. Conventional systemic evaluation (chest radiography, chest and abdomen CT, abdominal sonography, and so on) did not show any pathologic image. FDG PET-CT was then carried out. A hypermetabolic focus was revealed in the left hilum. In conclusion, from now on, FDG PET-CT will be considered as the first diagnostic process for patients presenting brain metastasis with an unknown primary tumor.     

Visualization of prostate cancer with 11C-choline positron emission tomography

BACKGROUND AND OBJECTIVE: Visualization of prostate cancer with positron emission tomography (PET) using 2-[18F]-2-deoxy-D-glucose (FDG) as radiopharmaceutical is limited by the low uptake of FDG in the tumor and by radioactivity excreted into the bladder. More specific PET radiopharmaceuticals would be welcome. Carbon-11 labeled choline (CHOL) is a new radiopharmaceutical potentially useful for tumor imaging as it is incorporated in the cell membranes as phosphatidylcholine. We prospectively studied the visualization of prostate cancer using CHOL PET. METHODS: A total of 25 consecutive patients with histologically proven prostate cancer and five patients with a benign prostate were included. PET images were performed with an ECAT HR(+) using 400MBq CHOL. Data acquisition was started at 5 minutes post-injection. Attenuation-corrected images were evaluated visually. Standardized uptake values (SUV) were calculated of the normal prostate gland and of the prostate tumor tissue. RESULTS: The normal prostate was visualized with a mean SUV of 2.3 (range 1.3-3.2). The primary tumor could be visualized with a mean SUV of 5.0 (range 2.4-9.5). Lymph node metastases >5mm could be identified. Non-specific uptake of CHOL was noticed in the intestines. Little to no radioactivity in the bladder was observed. CONCLUSION: Carbon-11-choline is avidly taken up in prostate cancer, both primary tumor and lymph node metastases, in the virtual absence of urinary radioactivity. These results confirm the early results obtained by others and permit further clinical research on the value of CHOL PET as a metabolic imaging technique in areas where conventional imaging have a limited sensitivity.     

FDG‐PET proves to be reliable in the diagnostic workup of a rare cardiac hemangioma

The noninvasive characterization of cardiac tumors is of clinical importance for surgical resection planning. Conventional radiological examinations like cardiac computed tomography (CT) or magnetic resonance imaging (MRI) may be misleading as benign cardiac lesions can present features suspicious for malignancy. Moreover, the low prevalence of cardiac tumors may additionally hamper a sound diagnosis. However, fluorodeoxyglucose‐positron emission tomography (FDG‐PET) has proven to be a reliable tool for cardiac tumor characterization. Here, FDG‐PET/CT imaging of a 50‐year‐old man suffering from a cardiac tumor is presented. Despite CT and MRI signs of malignancy, FDG‐PET characterized the tumor as benign. Histology confirmed the FDG‐PET prediction and revealed a pericardial capillary hemangioma. Thereby, it seems important to integrate FDG‐PET in the diagnostic workup of cardiac tumors.     

Clinical value of [18-F]] fluorodeoxyglucose positron emission tomography imaging in soft tissue sarcomas

OBJECTIVE: To evaluate positron emission tomography (PET) using 2-fluoro-2-deoxy-D-glucose (FDG) for clinical application in soft tissue sarcomas. SUMMARY AND BACKGROUND DATA: FDG PET is a promising noninvasive method for the preoperative assessment of soft tissue sarcomas and may complement radiologic tomography. METHODS: Data from 50 consecutive patients with 59 masses, either suspicious for primary or locally recurrent soft tissue sarcoma, were prospectively gathered. The semiquantitative FDG uptake (standardized uptake values [SUVs]) was calculated in tumor and normal tissue (muscle). Histopathology of surgical specimens and follow-up data were used as control criteria. RESULTS: In primary soft tissue sarcomas, PET displayed a sensitivity of 91% and a specificity of 88%. Local recurrence was detected with a sensitivity of 88% and a specificity of 92%. All intermediate-grade and high-grade soft tissue sarcomas (primary and locally recurrent) were visualized with a precise differentiation from muscle. Fifty percent of the low-grade sarcomas showed an FDG uptake equivalent to muscle (false-negative results in one primary and three recurrent soft tissue sarcomas). Benign soft tissue tumors (e.g., lipoma, leiomyoma, ganglion) did not accumulate FDG. Inflammation resulted in an increased FDG uptake. The semiquantitative FDG uptake (SUVs) correlated with tumor grade but not with size and histologic type. CONCLUSION: High-grade and intermediate-grade soft tissue sarcomas are amenable to PET imaging, whereas low-grade lesions may not be depicted. SUVs for FDG correlate with tumor grade in soft tissue sarcomas. Benign soft tissue tumors are differentiated from higher-grade soft tissue sarcomas. These data show that FDG-PET can complement preoperative radiologic assessment for soft tissue sarcomas and that FDG-PET is a powerful diagnostic tool for detecting high-grade and intermediate-grade local recurrence.     

Comparison of [18 F]fluorocholine and [18 F]fluorodeoxyglucose for positron emission tomography of androgen dependent and androgen independent prostate cancer

PURPOSE: Positron emission tomography (PET) imaging is used for the metabolic evaluation of cancer. [18F]fluorodeoxyglucose (FDG) is commonly used as a radiotracer but its low cellular uptake rate in prostate cancer limits its usefulness. We evaluated the novel choline analog [18F]fluorocholine (FCH) for detecting androgen dependent and androgen independent prostate cancer, and its metastases. MATERIALS AND METHODS: The cellular uptake of FCH and FDG was compared in cultured prostate cancer cells (LNCaP and PC-3). FCH and FDG were injected into nude mice xenografts (CWR-22 and PC-3) and radiotracer uptake in various organs were evaluated. Patients with androgen dependent (9) and independent (9) prostate cancer were studied by FCH and FDG PET. RESULTS: FCH uptake was 849% and 60% greater than FDG uptake in androgen dependent (LNCaP) and independent (PC-3) cells, respectively. The addition of hemicholinium-3 (5 mM.) 30 minutes before radiotracer administration inhibited FCH uptake by 79% and 70% in LNCaP and PC-3 cells, respectively, whereas FDG uptake was not significantly affected. Although nude mice xenografts showed that FDG uptake was equal to or greater than FCH uptake, clinical imaging in patients demonstrated 2 to 4-fold higher uptake of FCH in those with androgen and androgen independent prostate carcinoma (p <0.001). More lesions were detected by FCH than by FDG in primary tumors, osseous metastases and soft tissue metastases. CONCLUSIONS: In vitro data demonstrated greater FCH than FDG uptake in androgen dependent (LNCaP) and androgen independent (PC-3) prostate cancer cells. Although the murine xenograft data showed greater accumulation of FDG than FCH in PC-3 tumors, PET in humans showed that FCH was better than FDG for detecting primary and metastatic prostate cancer. Overall the data from this study suggest that FCH is preferable to FDG for PET of prostate carcinoma and support the need for future validation studies in a larger number of subjects.     

Diagnostic value of 18F-FDG positron emission tomography for detection and treatment control of malignant germ cell tumors

INTRODUCTION: The role of positron emission tomography (PET) with 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) is currently under evaluation in urologic oncology. The aim of the present study was to investigate the use of [18F]FDG positron emission tomography ([18F]FDG-PET) in the detection and treatment control of malignant germ cell tumors compared to computed tomography (CT). MATERIALS AND METHODS: Thirty-two PET studies and CT scans were carried out in 23 patients with histologically proven germ cell tumors (10 seminomas, 12 non-seminomatous germ cell tumors (NSGCT), 1 unclassified serologic recurrent disease) Lugano stage I-III. The scans were done either after initial diagnosis (n = 21) and/or within 3-45 days after chemotherapy was completed (n = 11). PET and CT were validated either by histology (n = 7) or clinical follow-up of 6-11 months after the last PET study has been performed (n = 16). Sensitivity, specificity, accuracy, positive and negative predictive values were determined for PET and CT. Differences between PET and CT for parameters of diagnostic value were evaluated by chi(2) test. RESULTS: Although not statistically significant, the sensitivity, accuracy and negative predictive value were higher for PET than for CT with respect to the detection of metastatic infradiaphragmatic and supradiaphragmatic lesions after initial diagnosis. The specificity and positive predictive value of PET and CT were comparable. After chemotherapy, PET was found to be significantly superior in specificity and accuracy compared to CT with respect to infradiaphragmatic lesions (p < 0.05). False-positive PET findings in supradiaphragmatic lesions after chemotherapy occurred in the case of inflammatory processes and resulted in a loss of specificity and accuracy compared to CT (p < 0.05). CONCLUSIONS: These preliminary results demonstrate [18F]FDG-PET to be a useful diagnostic tool for the initial staging and treatment control in patients with germ cell tumors. Possible advantages compared to CT, however, are as yet not clearly defined. The possibility of false-positive PET findings due to reactive supradiaphragmatic inflammatory processes early after chemotherapy have to be considered.     

The interest of 18FDG-PET in the management of testicular cancer

The key to prognosis. Initial staging and early recurrence diagnosis are key parameters in the treatment and outcome of testicular cancer. Initial staging. It is difficult using conventional modalities, which can miss node involvement and are non-specific since enlargement does not rhyme with involvement. 18FDG PET improves the accuracy of initial staging. Residual mass and recurrences. Existence of residual mass or enhancement of its Volume in the presence of an otherwise beneficial chemotherapy is difficult to manage. Several studies have demonstrated the value of 18FDG imaging in such cases. As for follow-up whole body 18FDG can prevent multiple diagnostic imaging and can diagnose recurrences with greater diagnostic accuracy than with other imaging modalities.     

Staging and Assessment of Lymph Node Involvement by18F-Fluorodeoxyglucose–Positron Emission Tomography in Invasive Extramammary Paget''s Disease

BACKGROUND: 18F-Fluorodeoxyglucose (FDG)-positron emission tomography (PET) is a functional and metabolic imaging modality that is efficacious in nodal staging and detection of extranodal involvement for malignant tumors. OBJECTIVE: We describe the novel use of PET for staging patients with invasive extramammary Paget's disease (EMPD) and discuss the potential advantages of this technology relative to other diagnostic modalities. METHODS: We evaluated three patients with invasive EMPD whose staging was made by PET at Hokkaido University Hospital. RESULTS: All lymph nodes detected by PET were over 10 mm. Distant internal metastases were not seen in all cases. PET failed to detect 10 and 5 to 7 mm nodal involvement but succeeded in detecting nodes over 10 mm. CONCLUSIONS: These data suggest that PET may be useful in determining disease activity at the time of initial diagnosis but is less useful and proves difficult to detect a small or subclinical involvement. This is the first report of PET being used for invasive EMPD.     

Molecular Imaging for Evaluation of Viable Testicular Cancer Nodal Metastases

Purpose of Review

Determining the metastatic viability of suspicious retroperitoneal nodes in testicular cancer with conventional imaging is challenging. The aim of this report is to review recent evidence in the utilization of novel imaging modalities to assess viable testicular cancer nodal metastases.

Recent Evidence

Testicular germ cell tumors (TCGTs) follow a predictable lymphatic metastatic spread to the retroperitoneum. Accordingly, retroperitoneal imaging is critical in staging, assessing treatment response, and evaluating for recurrence. Conventional computed tomography (CT) imaging is effective in diagnosing pathologically enlarged lymph nodes but lacks the molecular information to determine if suspicious nodes harbor viable tumor. Positron emission tomography (PET) with the metabolic radiotracer 2-deoxy-2-[¹⁸F]fluoro-d-glucose (¹⁸F-FDG or FDG) has been shown to be useful in determining the presence of or absence of viable tumor after chemotherapy for seminoma, but its role with non-seminomatous germ cell tumors (NSGCTs) and other clinical scenarios is limited. Patients with residual masses after chemotherapy for NSGCT present a difficult challenge because surgical resection carries a high degree of morbidity despite many patients only harboring fibrosis on final pathology. Current imaging modalities are unable to effectively differentiate fibrosis from viable tumor on preoperative imaging. Novel molecular imaging techniques present promising opportunities to improve diagnosis in these patients.

Summary

Novel imaging platforms have potential to improve the ability to determine viable nodal metastases regardless of size and structure but confirmatory studies are currently lacking.

     

Fluorine-18-fluorodeoxyglucose positron emission tomography is useless for the detection of local recurrence after radical prostatectomy.

OBJECTIVE: After radical retropubic prostatectomy a rise of the prostate-specific antigen (PSA) indicates a local recurrent or metastatic disease. If the bone scan shows no apparent bone metastasis, morphological imaging methods like x-ray computed tomography, magnetic resonance imaging or transrectal ultrasound often cannot distinguish between postoperative scar and local recurrence. Therefore we investigated the feasibility of fluorine-18-fluorodeoxyglucose positron emission tomography (F-18 FDG PET) for metabolic characterization of prostatic cancer, especially for differentiation of scar or recurrent prostate cancer after radical prostatectomy. METHODS: Dynamic PET with 370 MBq F-18 deoxyglucose (F-18 FDG) up to 60 min p.i. was performed in 2 patients with biopsy-proven benign prostatic hyperplasia, in 11 patients with a histologically proven prostate cancer prior to radical retropubic prostatectomy (RRP) and 7 patients with suspected local recurrence (with negative bone scan) after RRP prior to biopsy of anastomosis (3 local recurrence, 4 postoperative scar). RESULTS: Prostate cancer showed a very low F-18 FDG uptake. The placement of regions of interest was only possible by the use of other imaging methods. There was not difference between the F-18 FDG uptake of benign prostate hyperplasia, prostate carcinoma, postoperative scar or local recurrence after radical prostatectomy. CONCLUSION: F-18 FDG seems not to be useful to distinguish between postoperative scar and local recurrence after radical prostatectomy.     

The application of positron emission tomographic imaging with fluorodeoxyglucose to the evaluation of breast disease.

Positron emission tomography (PET) is a computer-aided tomographic imaging technique that uses positron-emitting compounds to trace biochemical processes of tissue, and construct images based on them. The authors applied a whole-body PET imaging technique to patients with breast masses or mammographic abnormalities using the isotope 2-[F-18]-fluoro-2-deoxy-D-glucose (FDG), in a clinical trial to evaluate the feasibility of using PET to identify primary breast cancer, axillary lymph node involvement, and systemic metastases, before surgical resection. Fourteen patients have been entered on this study, 10 of whom proved to have breast cancer. Positron emission tomography correctly predicted the nature of 12 of the 14 primary breast lesions, and correctly determined the lymph node status of 11 of the 14 patients. The authors conclude that PET with FDG has potential as a diagnostic modality for detection of primary breast cancer, particularly in the patient with radiodense breasts by conventional mammography, and that it has potential for the preoperative identification of axillary lymph node metastases.     

克氏综合征合并原发纵隔恶性生殖细胞肿瘤(附1例报告并文献复习)

目的:探讨克氏综合征合并原发纵隔恶性生殖细胞肿瘤临床特点及诊治方法。方法:对1例克氏综合征合并原发纵隔恶性生殖细胞肿瘤患者进行相关的实验室内分泌学检查和染色体核型分析,并对纵隔原发病灶行根治性切除术,术后给予5个疗程的顺铂、博莱霉素和长春新碱化疗,并联合放疗。结果:内分泌多项指标异常,染色体核型为47,XXY,手术切除标本病理提示为混合性生殖细胞源性恶性肿瘤(成熟畸胎瘤,精原细胞瘤和卵黄囊瘤成分),随访2年肿瘤无复发。结论:克氏综合征合并原发纵隔恶性生殖细胞肿瘤的正确诊断,及早合理治疗对改善患者精神状态,提高生活适应能力等具有重要的临床意义。     

PET—CT在前列腺癌诊断与临床分期的应用

目的探讨PET—CT应用于前列腺癌诊断及分期的临床价值。方法2008年1月至2011年1月新疆自治区人民医院泌尿外科收治前列腺肿瘤病例中,病理类型最终确诊为前列腺癌者有47例接受了全身PET—CT检查。检查范围包括前列腺原发肿瘤、区域淋巴结及全身脏器,将PET—CT结果参照手术／病理结果进行评价分析。结果47例患者中1例未发现原发病灶,此外PET—CT与常规检查各有1例假阴性,准确性均高达95．7％,差异无统计学意义。35例I、Ⅱ期患者中18例髂血管淋巴结转移,PET-CT检查的敏感性59．6％、特异性81％、准确性70．3％,优于B超、磁共振检查;PET—CT发现4例患者合并远处转移并经穿刺证实,准确性100％。结论PET—CT对于发现前列腺癌原发肿瘤、区域淋巴结转移均优于B超、磁共振检查,且对于远处转移具有较精确的检测能力,对于前列腺癌术前诊断及分期有较好的临床价值。     

Klinefelter's syndrome and precocious puberty: a harbinger for tumor

Boys with Klinefelter's syndrome are at an increased risk of precocious puberty. Most cases are either idiopathic or due to a mediastinal tumor. Patients with Klinefelter's syndrome are at a high risk of primary, extragonadal germ cell tumors, which are usually nonseminomatous, but can be a mixed type with seminomatous elements. The differential diagnosis of precocious puberty includes mediastinal tumors, especially in boys with Klinefelter's syndrome.