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

Positron emission tomography (PET) with the use of ((18)F)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.

Post transplant lymphoproliferative disease in pediatric solid organ transplant patients: a possible role for [18F]-FDG-PET(/CT) in initial staging and therapy monitoring.

Post transplant lymphoproliferative disease (PTLD) is a severe complication after solid organ or bone marrow transplantation. In pediatric transplant recipients PTLD is the most common malignancy. The aim of this study was to evaluate a possible role for positron emission tomography with [18F]-2-fluoro-2-desoxy-glucose (FDG) in the initial staging and in therapy monitoring of pediatric patients suffering from biopsy-proven CD20-positive PTLD after solid organ transplantation. Seven pediatric patients were included. All available imaging studies - CT (n=15), MRI (n=16) and PET/PETCT (n=16) - were reviewed on a lesion by lesion base. The performance of FDG-PET in the initial staging and during therapy with a chimeric anti-CD20 antibody was compared to conventional cross sectional imaging and correlated with the clinical outcome. FDG-PET identified all sites of disease as shown by CT/MRI and helped to clarify the significance of equivocal findings. The initial stage of disease was correctly identified by FDG-PET alone when compared to CT/MRI. During therapy, FDG-PET was superior to conventional cross-sectional imaging in the early evaluation of response.

[Positron emission tomography (PET) for diagnosis and monitoring of treatment for urological tumors]. / Positronenemissionstomographie (PET) zur Diagnostik und zum Therapiemonitoring bei urologischen Tumoren.

Positron emission tomography (PET) using ((18)F)2-fluoro-D-2-desoxyglucose (FDG) has been shown to be a highly sensitive and specific imaging modality in the diagnosis of primary and recurrent tumors and in the control of therapies in numerous non-urologic cancers. It was the aim of this review to validate the significance of PET as a diagnostic tool in malignant tumors of the urogenital tract. A systematic review of the current literature concerning the role of PET for malignant tumors of the kidney, testicles, prostate, and bladder was carried out. The role of FDG PET for renal cell cancer can be seen in the detection of recurrences after definitive local therapy and metastases. The higher sensitivity of PET in comparison to other therapeutic modalities (CT, ultrasound, MRI) in recurrent and metastatic renal cell cancer suggests a supplemental role of this diagnostic procedure to complement other imaging modalities.The clinical value of PET is established for the identification of vital tumor tissue after chemotherapy of seminomatous germ cell tumors. This diagnostic method has little significance for primary tumor staging and diagnosis of non-seminomatous germ cell tumor because of the high probability of false-negative results in adult teratomas. FDG PET is not sensitive enough in the diagnosis of primary or recurrent tumors in prostate or bladder cancer. Also PET did not prove to be superior to conventional bone scintigram in the detection of mostly osteoblastic metastases in prostate cancer. The recent use of alternative tracers, which are partly not eliminated by urinary secretion (acetate, choline) has increased the sensitivity and specificity of PET also in this tumor entity so that further clinical investigations are needed to validate these technical modifications in their significance for this imaging modality. PET appears to be sufficiently evaluated only for the diagnostic follow-up of patients with seminomatous germ cell tumors after chemotherapy to regard it is the diagnostic tool of first choice. For all other tumors of the urogenital tract this proof is still awaited.

Pre-operative localisation of hyperfunctional parathyroid tissue with 11C-methionine PET.

PURPOSE: Previous studies have shown high sensitivity of positron emission tomography (PET) with 11C-methionine in the pre-operative localisation of parathyroid adenoma and hyperplasia. Nonetheless, in secondary and tertiary hyperparathyroidism (HPT) and in patients with recurrent disease, pre-operative localisation of adenomatous (PTA) or hyperplastic tissue is still a problem with all available methods. The aim of this study was to define the optimal imaging protocol and to compare the diagnostic value of 11C-methionine PET and 99mTc-methoxyisobutylisonitrile (MIBI) single-photon emission computed tomography (SPECT): in particular, we wished to define the benefit of 11C-methionine in those patients with inconclusive or negative conventional imaging. METHODS: Thirty highly pre-selected patients with HPT were enrolled. Sixteen patients had primary HPT, 12 patients had secondary HPT, and two patients had recurrences of parathyroid carcinomas. All patients had ultrasound of the neck, dual-phase scintigraphy with 99mTc-MIBI and PET with 11C-methionine. SUV(parathyroid)/SUV(cervical soft tissue) (target-to-background) and SUV(parathyroid tissue)/SUV(thyroid tissue) (target-to-non-target) ratios were calculated. After surgery, histology of specimens was obtained in all patients but one. RESULTS: In 12 patients with secondary or tertiary HPT, 36 hyperplastic parathyroid glands were histologically verified. Twenty-five of 36 lesions (69%) were detected with 11C-methionine PET and 17 (47%) with 99mTc-MIBI scintigraphy. PET studies were positive in 17/18 (94%) cases in which HPT was related to adenomas or carcinomas. 99mTc-MIBI scintigraphy/SPECT yielded pathological lesions in 9/18 cases (50%). All eight atypical localisations of parathyroid glands were detected with PET but only six of the eight were detected with 99mTc-MIBI scintigraphy/SPECT. In 10/11 patients with recurrent HPT and non-diagnostic scintigraphy/SPECT, hyperfunctional parathyroid tissue was identified with 11C-methionine PET. The highest SUV(parathyroid)/SUV(cervical soft tissue) ratio was found 10 min, and the highest SUV(parathyroid tissue)/SUV(thyroid tissue) ratio 40 min post injection. In three patients clear delineation of hyperfunctional tissue was only achieved after 40 min post injection. CONCLUSION: 11C-methionine PET is a clinically useful method in highly pre-selected patients with recurrent primary HPT as well as in secondary and tertiary HPT if ultrasound and 99mTc-MIBI SPECT are inconclusive or negative. PET imaging of atypical PTA localisations is more accurate than conventional scintigraphy. In order to achieve optimal contrast of parathyroid glands versus thyroid tissue and adjacent soft tissue, imaging at both 10 min and 40 min is recommended.

Positron emission tomography with 11C-acetate and 18F-FDG in prostate cancer patients.

Visualisation of primary prostate cancer, its relapse and its metastases is a clinically relevant problem despite the availability of state-of-the-art methods such as CT, MRI, transrectal ultrasound and fluorine-18 fluorodeoxyglucose positron emission tomography ((18)F-FDG PET). The aim of this study was to evaluate the efficacy of carbon-11 acetate and (18)F-FDG PET in the detection of prostate cancer and its metastases. Twenty-five patients were investigated during the follow-up of primary prostate cancer, suspected relapse or metastatic disease using (11)C-acetate PET; 15 of these patients were additionally investigated using (18)F-FDG PET. Fourteen patients were receiving anti-androgen treatment at the time of the investigation. Lesions were detected in 20/24 (83%) patients using (11)C-acetate PET and in 10/15 (75%) patients using (18)F-FDG PET. Based on the results of both PET scans, one patient was diagnosed with recurrent lung cancer. Median (18)F-FDG uptake exceeded that of (11)C-acetate in distant metastases (SUV =3.2 vs 2.3). However, in local recurrence and in regional lymph node metastases, (11)C-acetate uptake (median SUVs =2.9 and 3.8, respectively) was higher than that of (18)F-FDG (median SUVs =1.0 and 1.1, respectively). A positive correlation was observed between serum PSA level and both (11)C-acetate uptake and (18)F-FDG uptake. (11)C-acetate seems more useful than (18)F-FDG in the detection of local recurrences and regional lymph node metastases. (18)F-FDG, however, appears to be more accurate in visualising distant metastases. There may be a role for combined (11)C-acetate/(18)F-FDG PET in the follow-up of patients with prostate cancer and persisting or increasing PSA.

Monitoring isotretinoin therapy in thyroid cancer using 18F-FDG PET.

Treatment with isotretinoin (13-cis-retinoic acid, 13-cis-RA) is a recent additional option in advanced, otherwise intractable differentiated thyroid cancers. The aim of this study was to evaluate fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG PET) in the prediction and the monitoring of response to 13-cis-RA therapy. Twenty-one patients with advanced differentiated thyroid cancers were investigated using 18F-FDG PET and iodine-131 whole-body scans before and 3, 6 and 9 months after initiation of 13-cis-RA therapy. After 9 months, 13-cis-RA treatment was discontinued and imaging procedures repeated 3 months later. Average 18F-FDG uptake (SUV) decreased significantly during 13-cis-RA therapy but subsequently increased in five of eight patients after withdrawal of 13-cis-RA. 18F-FDG uptake (SUV) 3 months after onset of 13-cis-RA therapy was significantly lower in patients who developed increased 131I uptake in their tumour sites than in patients with no subsequent increase in 131I uptake. There was no relationship between serum thyroglobulin level on the one hand and simultaneously measured 131I or 18F-FDG uptake on the other hand. There was a tendency towards lower 18F-FDG uptake in tumour manifestations with a better outcome. Therefore, 18F-FDG PET at 3 months after the start of treatment promises to differentiate between those patients who will eventually benefit from 13-cis-RA and those who will not. In conclusion, these data indicate that 18F-FDG PET is a useful tool for the evaluation and monitoring of adjuvant therapy with 13-cis-RA in thyroid cancer.

Glucose metabolism of the thyroid in autonomous goiter measured by F-18-FDG-PE.

The radiolabeled glucose analogue F-18-Fluoro-Deoxyglucose (F-18-FDG) and Positron Emission Tomography (PET) were used to measure glucose metabolism of the thyroid in vivo. We evaluated patients with autonomous goitre before therapy with radioiodine in comparison to patients with normal thyroids. 30 patients with autonomous goitre underwent scanning the day before radioiodine therapy. 19 patients with head or brain tumours and normal thyroids were the controls. Overall F-18-FDG uptake was determined for all thyroids and proved to be significantly higher in autonomy patients compared to controls and in disseminated autonomous goitre slightly but not significantly higher than in focal autonomy. In autonomy patients F-18-FDG uptake increased with increasing radioiodine uptake and shorter radioiodine half-life. These results indicate that glucose metabolism is enhanced in the thyroids of patients with focal and disseminated autonomy. The negative correlation of radioiodine half-life and glucose metabolism as well as the positive correlation of radioiodine uptake and glucose metabolism suggest connections of glucose metabolism and iodine-dependent hormone synthesis in thyroid cells.

Optimal scan time for fluorine-18 fluorodeoxyglucose positron emission tomography in breast cancer.

Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) has proven useful in the differentiation of various tumour entities, including breast cancer. In patients with primary breast cancer we performed a 3-h imaging protocol to examine possible improvements in tumour detectability and image contrast. Twenty-nine patients with primary breast cancer with a diameter of >/=2 cm that was demonstrated to be malignant by biopsy or surgery were injected with 370-740 MBq 18F-FDG and scanned in the prone position. Data were acquired 0-40 min, 1.5 h and 3.0 h after injection. After correction for measured attenuation, decay and scatter and iterative reconstruction, standardised uptake values (SUVs) and tumour-to-non-tumour and tumour-to-organ ratios were calculated. Visual analysis was performed using transverse, sagittal and coronal slices as well as 3D reprojection images. Tumour-to-non-tumour and tumour-to-organ ratios were significantly higher for the 3-h images than for the 1.5-h images. SUVs did not increase to the same extent. Lesion detectability was 83% in 1.5-h images compared to 93% in 3-h images. We conclude that tumour contrast in breast cancer is improved by starting the PET acquisition at 3 h p.i. rather than at 1.5 h p.i.

Glucose metabolism of the thyroid in Graves' disease measured by F-18-fluoro-deoxyglucose positron emission tomography.

The radiolabeled glucose surrogate F-18-fluoro-deoxyglucose (F-18-FDG) and positron emission tomography (PET) were used to measure glucose metabolism of the thyroid in vivo. We evaluated patients with Graves' disease before therapy with radioiodine in comparison to patients with normal thyroids. Thirty-six patients with Graves' disease underwent scanning the day before radioiodine therapy. Twenty patients with head tumors and normal thyroids were the controls. Overall F-18-FDG uptake was determined for all thyroids and modeling of glucose metabolism was performed in order to differentiate between glucose concentration in the fractional blood volume, glucose transport, and glucose utilization. F-18-FDG uptake was significantly higher in Graves' disease patients compared with controls. In these patients F-18-FDG uptake increased with increasing antithyroid antibodies and shorter radioiodine half-life. Modeling of glucose metabolism revealed substantial differences in thyroid F-18-FDG utilization constants (k3 values) corresponding to enhanced local metabolic rates in Graves' disease. No significant differences in the remaining rate constants and the fractional blood volume were detected. These results indicate that glucose metabolism is enhanced in the thyroid of Graves' disease patients not only due to enhanced fractional blood volume but to enhanced utilization. Whether a lymphocytic infiltration or thyroid epithelial cells utilize this surplus of glucose cannot be determined using in vivo PET measurements in humans. Still, the correlation of radioiodine half-life and glucose hypermetabolism suggests direct or nondirect connections of glucose metabolism and hormone synthesis in thyroid cells.

Redifferentiation therapy with retinoids: therapeutic option for advanced follicular and papillary thyroid carcinoma.

During the course of tumor progression the differentiated morphologic and functional characteristics of differentiated thyroid carcinomas (DTC) disappear. This corresponds to more aggressive growth, metastatic spread, and loss of iodine uptake. Experimental data give strong evidence that differentiated functions of iodine metabolism can be reinduced by retinoic acids. Results of a study performed in patients with advanced DTC are presented. Twenty patients with DTC (eight follicular, seven papillary, five oxyphilic) were selected for treatment with retinoic acid 1.5 mg/kg body weight/day over 5 weeks. All patients had advanced tumor stages with prior operative and radioiodine treatment. Extensive tumor invasion, distant metastatic spread, or insufficient or no radioiodine uptake precluded any conventional therapeutic option. The aim was to assess the changes under retinoid treatment. Iodine uptake increased in eight patients (three follicular, three papillary, two oxyphilic). Thyroglobulin (TG) as parameter for tumor mass and differentiation increased in 12 (63%) patients, decreased in 6 (32%), and did not change in 1 (5%). Retinoids do have an effect on differentiation status of DTC, reinducing iodine uptake in 50% of patients. TG levels do not always parallel a response in iodine uptake.