Prognostic value of functional tumor burden on 68Ga-DOTATOC PET/CT in patients with pancreatic neuro-endocrine tumors.

Despite their relative quiescence, pancreatic neuro-endocrine tumors (pNET) can correspond to various presentations and outcomes. Several prognostic factors have been identified, including maximal standardized uptake value of the most intense focus (maxSUVmax) on Positron Emission Tomography (PET) with a somatostatin analogue. Herein, we investigate the prognostic value on progression free-survival of the total functional tumor volume (TFTV) measured by 68Ga-DOTATOC PET. From patients who underwent 68Ga-DOTATOC PET from 2008 to 2014, we selected consecutive patients with G1 or G2 pNET (2010 World Health Organization classification), at least one abnormal focus on PET and available follow-up data. TFTV was computed by summing the volumes of all pathological foci, delineated use of 41% of its SUVmax for each threshold focus. Fifty patients were included. During the follow-up period, 33 patients had stable or responsive disease (66%; median duration 28.5 months; range 6.3-77.7 months) and 17 patients experienced disease progression (34%; median progression time 21 months; range 6.7-44.7 months). Median PFS was 43.5 months. The best TFTV cut-off for predicting progression within 24 months was 13.8 cm3. Multivariate analysis determined that TFTV greater than 13.8 cm3 was the only criterion considered a significant risk factor for tumor progression (HR 2.9; p=0.0003). A significant difference in PFS was observed for TFTV (<13.8 vs. ≥ 13.8 cm3: median not reached vs. 25 months; p=0.0001). Our study suggests that 68Ga-DOTATOC TFTV measured on PET images is a valuable prognostic biomarker in patients with well-differentiated pNETs of all stages.

[PET/CT and biochemical recurrence of prostate adenocarcinoma: Added value of 68Ga-PSMA-11 when 18F-fluorocholine is non-contributive]. / TEP/TDM et récidive biologique d'adénocarcinome prostatique : apport du 68Ga-PSMA-11 lorsque la 18F-fluorocholine n'est pas contributive.

INTRODUCTION: Since April 201, we have introduced PET/CT using a ligand of prostate-specific membrane antigen labeled with gallium-68 (PSMA-11). We aimed to evaluate its positivity rate and impact in patients presenting biochemical recurrence of prostate cancer whose 18F-fluorocholine (FCH) PET/CT was non-contributive. PATIENTS AND METHOD: Patients were prospectively included between April and December 2016. PET/CT was performed 60min after injection of 2MBq/kg of body mass of 68Ga-PSMA-11. Three anatomical areas were considered: prostatic lodge, pelvic lymph nodes and distant locations. The impact of PSMA-11 PET/CT was assessed by comparing changes in therapeutic strategy decided during multidisciplinary meeting. RESULTS: Thirty-three patients were included. The mean PSA serum level measured on the month of the PSMA-11 PET/CT was 2,8ng/mL. Twenty-five (76%) PSMA-11 PET/CT were positive, 7 (21%) negative and 1 (3%) equivocal. Of 11 patients whose FCH PET/CT showed equivocal foci, PSMA-11 PET/CT confirmed those foci in 5 cases. Follow-up was available for 18 patients (55%). PSMA-11 PET/CT results led to a change in management in 12 patients (67%). CONCLUSION: 68Ga-PSMA-11 PET/CT is useful in detecting recurrence of prostate cancer, by identifying residual disease which was not detected on other imaging modalities and by changing management of 2 patients out of 3. LEVEL OF EVIDENCE: 5.

Hyperparathyroidism in pregnancy and 99mTc-MIBI scintigraphy.

INTRODUCTION: Primary hyperparathyroidism (PHPT) during pregnancy can be responsible for serious maternal and foetal complications and should be treated by elective low-risk, minimally invasive surgery. Preoperative assessment of hyperfunctioning parathyroid glands is classically based on high-resolution neck ultrasound (US) and 99mTc-sestamibi/123I scintigraphy. However, administration of any radiopharmaceutical during pregnancy must be limited and justified and US alone may be sufficient to localize an abnormal parathyroid gland. CASE REPORT: We report the case of a 4-month pregnant woman with severe primary hyperparathyroidism, in whom US failed to localize the abnormal parathyroid gland. 99mTc-sestamibi scintigraphy was performed in preference to 18-fluorocholine (FCH)-PET/CT on the basis of a multidisciplinary decision. As 99mTc-MIBI demonstrated an hyperfunctioning right inferior parathyroid, 123I was not administered. A large right paravertebral parathyroid adenoma was successfully removed, as confirmed by decreased postoperative serum parathyroid hormone and calcium levels. The eutrophic newborn infant was delivered at term, with normal serum calcium and TSH levels. DISCUSSION: In pregnant women with primary hyperparathyroidism, US alone may be sufficient when it localizes the abnormal parathyroid gland, allowing elective low-risk minimally invasive surgery. Otherwise, a multidisciplinary approach is mandatory to select the radiopharmaceutical that can be safely used to identify the hyperfunctioning parathyroid gland with minimal risks for the foetus.

Prospective comparison of FDG and FET PET/CT in patients with head and neck squamous cell carcinoma.

AIM: The clinical usefulness of 2-deoxy-2-[F-18]fluoro-D-glucose-positron emission tomography (FDG-PET) in head and neck squamous cell carcinoma (HNSCC) is now well-documented. However, its sensitivity is greater than its specificity due to false-positive results in inflammatory or infectious lesions, which are frequent in this area, in particular after treatment by surgery and/or radiotherapy. O-2-fluoro-(18F)-ethyl-L-thyrosine (FET) has been reported not to be taken up by such lesions, and a preliminary study indicated that this may be clinically useful in HNSCC. We performed a prospective study to compare the diagnostic performances of FDG and FET PET/CT in the different settings of HNSCC. MATERIALS AND METHODS: Twenty-seven patients (20 men and seven women, aged 48-76, among 30 patients included) and 69 suspected cancer sites are now evaluable on basis of postsurgical histology and/or follow-up greater than 6 months; 15 patients were referred for initial staging and 12 during posttherapy follow-up, a recurrence being suspected in eight of them. FDG and FET PET/CT were performed on two different days, the patient fasting for 6 h, 1 h after injection of 5 MBq/kg of body mass of each radiopharmaceutical. Both PET/CT examinations were blind read more than 6 months after the end of inclusions in a random order for each tracer and with a time interval greater than 1 month between FDG and FET PET/CT blind readings. RESULTS: Overall diagnostic performances, derived from blind reading: FDG PET/CT on a per patient basis: sensitivity 100%, specificity 71%, accuracy 93%; FDG PET/CT on a per site basis: sensitivity 95%, specificity 63%, accuracy 83%; FET PET/CT on a per patient basis: sensitivity 70%, specificity 100%, accuracy 78%; FET PET/CT on a per site basis: sensitivity 64%, specificity 100%, accuracy 78%. At site level, sensitivity was significantly greater with FDG (p<0.02) and specificity with FET (p<0.01). The statistical level of significance was not reached at patient level. CONCLUSION: Although its good specificity was confirmed, FET did not appear to be suited as a first-line PET tracer in HNSCC imaging and cannot replace FDG for staging due to insufficient sensitivity. However, it was useful in a few selected cases to favor a wait and see attitude when a FDG+ FET- focus was discovered in patients referred for systematic FDG PET during follow-up. In contrast, second primary cancers should not be ruled out if FDG was clearly positive in the lungs or the digestive tract.

Pathology underrates colon cancer extranodal and nodal metastases; ex vivo radioimmunodetection helps staging.

PURPOSE: Colorectal carcinoma is frequently accompanied by small lymph nodes metastases that often escape pathologic examination. We evaluated whether ex vivo radioimmunodetection with the Affinity Enhancement System (AES) could improve detection of mesocolonic metastases. EXPERIMENTAL DESIGN: A bivalent 111In-labeled hapten was injected (16 patients) 4 days after a bispecific antibody (anticarcinoembryonic antigen, antihapten). Surgery was done 1 to 3 days later, and radioactive uptake in the mesocolon was recorded. Extensive pathologic examination of the mesocolon (reference method) was done after fat dissolution. This method visualizes all lymph nodes but is not in routine use. RESULTS: The reference method disclosed 705 nodes. There was no significant difference between the number of node metastases detected by AES or by the reference method (16 versus 17). Better detection would have been obtained by AES than by routine pathology (P<0.01). In addition 12 extranodal metastases were found in this study of which eight were detected by AES. The prognostic importance of such extranodal metastases has been underlined in the literature. Routine pathology combined with AES would have disclosed all node metastases and 86% of total metastases versus 35% by routine pathology alone. CONCLUSIONS: Ex vivo radioimmunodetection could improve nodal and extranodal metastases detection in patients with colorectal cancer. Its value for improving pathologic analysis, together with the effect of these small metastases on prognosis, should be further evaluated. The benefit of adjuvant chemotherapy for patients upstaged with radioimmunodection should also be assessed because adjuvant chemotherapy improves the 5-year survival of stage III patients.

[Use of PET for staging, treatment evaluation, and follow-up in esophageal cancers]. / Apport de la TEP au diagnostic, évaluation thérapeutique et suivi du cancer de l'oesophage.

FDG-(18F) PET can now be usually included in the treatment strategy of esophageal cancers for the pretreatment staging in operable tumours or for the diagnosis of recurrence. PET is also a good tool in conformal radiation therapy for improving the target coverage to treat the metabolic target volume or the biological target volume. Furthermore, PET seems to be interesting for evaluation of tumour response and could modify the treatment strategy after neoadjuvant chemotherapy or concurrent chemotherapy and radiation therapy. New radiotracers could allow advances in biological and molecular tumour delineation and contribute to change in treatment strategy based on functional and biological imaging.

MRI and FDG PET/CT findings in a case of probable Heidenhain variant Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease (CJD) is a neurodegenerative disease caused by the accumulation of a pathogenic isoform of a prion protein in neurons that is responsible for subacute dementia. The Heidenhain variant is an atypical form of CJD in which visual signs are predominant. This is a report of the case of a 65-year-old man with probable CJD of the Heidenhain variant, with topographical concordance between findings on magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose (FDG) photopenic areas on positron emission tomography (PET)/computed tomography (CT) for cortical parietooccipital lesions.

[Imaging and PET-CT of adult and childhood lymphoma]. / Imagerie radiologique et TEP scanner des lymphomes de l'adulte et de l'enfant.

Malignant lymphomas are lymphoproliferative disorders arising in both lymphoid tissue and non-lymphoid organ systems. Treatment rarely is surgical, and currently relies on a combination of chemotherapy and radiation therapy. The role of imaging is to determine the spread of the disease, to identify targets and to assess therapeutic response. Imaging techniques mainly use morphological criteria, and may underestimate infiltrative disease, as observed in bones. The frequent presence of residual masses after treatment usually prevents classification of patients as complete response. Over time, positron emission tomography (PET) with F18-fluorodeoxyglucose (FDG) has become a prominent part of the workup at diagnosis and during follow-up. Recently, PET has been integrated in the revised response criteria for malignant lymphoma.

Full modelling of the MOSAIC animal PET system based on the GATE Monte Carlo simulation code.

Positron emission tomography (PET) systems dedicated to animal imaging are now widely used for biological studies. The scanner performance strongly depends on the design and the characteristics of the system. Many parameters must be optimized like the dimensions and type of crystals, geometry and field-of-view (FOV), sampling, electronics, lightguide, shielding, etc. Monte Carlo modelling is a powerful tool to study the effect of each of these parameters on the basis of realistic simulated data. Performance assessment in terms of spatial resolution, count rates, scatter fraction and sensitivity is an important prerequisite before the model can be used instead of real data for a reliable description of the system response function or for optimization of reconstruction algorithms. The aim of this study is to model the performance of the Philips Mosaic animal PET system using a comprehensive PET simulation code in order to understand and describe the origin of important factors that influence image quality. We use GATE, a Monte Carlo simulation toolkit for a realistic description of the ring PET model, the detectors, shielding, cap, electronic processing and dead times. We incorporate new features to adjust signal processing to the Anger logic underlying the Mosaic system. Special attention was paid to dead time and energy spectra descriptions. Sorting of simulated events in a list mode format similar to the system outputs was developed to compare experimental and simulated sensitivity and scatter fractions for different energy thresholds using various models of phantoms describing rat and mouse geometries. Count rates were compared for both cylindrical homogeneous phantoms. Simulated spatial resolution was fitted to experimental data for (18)F point sources at different locations within the FOV with an analytical blurring function for electronic processing effects. Simulated and measured sensitivities differed by less than 3%, while scatter fractions agreed within 9%. For a 410-665 keV energy window, the measured sensitivity for a centred point source was 1.53% and mouse and rat scatter fractions were respectively 12.0% and 18.3%. The scattered photons produced outside the rat and mouse phantoms contributed to 24% and 36% of total simulated scattered coincidences. Simulated and measured single and prompt count rates agreed well for activities up to the electronic saturation at 110 MBq for the mouse and rat phantoms. Volumetric spatial resolution was 17.6 microL at the centre of the FOV with differences less than 6% between experimental and simulated spatial resolution values. The comprehensive evaluation of the Monte Carlo modelling of the Mosaic system demonstrates that the GATE package is adequately versatile and appropriate to accurately describe the response of an Anger logic based animal PET system.

[18F-FDG PET and bone scintigraphy to search for bone metastasis of lung cancer]. / TEP au FDG-(18F) et scintigraphie du squelette dans la recherche de métastases osseuses du cancer broncho-pulmonaire.

Initial staging of lung cancer is essential to determine the appropriate therapeutic strategy. 18F-FDG PET is currently considered to be the gold standard. 99mTc bisphonate bone scintigraphy has long been indicated to search for bone metastases but it is not know whether this exploration adds further information after an 18F-FDG PET scan. In order to answer this question, two observers unaware of the clinical situation reread PET scans and bone scintigraphies and results compared with other imaging findings. Between February 2001 and March 2004, 39 patients (13F, 26M, 62 +/- 11 yr) underwent 18FFDG PET and bone scintigraphy (mean interval 17 +/- 17 d). When the two explorations agreed for the diagnosis of bone extension, we considered that bone scintigraphy added nothing. When the two explorations were in disagreement, the other imaging examinations, the clinical features and laboratory results during the five-month minimal follow-up were used to establish the reference diagnosis. 18F-FDG PET and bone scintigraphy were in agreement in 29 patients (74%) with positive results in 12 (31%) and negative results in 17 (43%). The two explorations were in disagreement in 10 patients (26%). Among the five disagreement cases with positive bone scintigraphy and no bone anomaly on the 18F-FDG PET, the anomalies were benign and explained by clinical features (3 patients) or were not confirmed by the clinical course and laboratory results (2 patients). Among the 5 cases with a bone anomaly on the 18F FDG PET, no metastasis could be identified during clinical follow-up. Bone scintigraphy does not enable identification of any bone metastases which were not recognized on the PET scan and therefore should not be performed systematically. Using a computed tomography scan with the 18F-FDG PET could further limit the contribution of bone scintigraphy by providing more precision concerning foci identified on the PET scan.

Best sensitivity of 18F-FDOPA PET/CT to detect metastasis in one case of neuroendocrine tumour of the ileum. / Mejor rendimiento de la PET/TC con 18F-FDOPA para la detección de metástasis de un tumor neuroendocrino del íleon.

Neuroendocrine tumours (NET) are heterogeneous and frequently spread over the body, making their imaging difficult. With this aim, nuclear medicine imaging, using PET or SPECT with different tracers, has been proposed for decades, but there is currently no consensus on the most appropriate technique, even when only considering gastrointestinal NET. The case is presented of a 67year old woman with a well differentiated NET of the ileum with suspected recurrence, which was not detected by any imaging technique except 18F-FDOPA PET/CT. Subsequent follow up showed disease progression, which confirmed the true positivity of 18F-FDOPA. Using this case, we discuss and compare different radiotracers for the diagnosis of gastrointestinal NET, focusing on those embryologically originating from the mid-gut.

[Impact of computed tomography (CT) and 18F-deoxyglucose-coincidence detection emission tomography (FDG-CDET) image fusion for optimisation of conformal radiotherapy in non-small-cell lung cancers]. / Tomographie par émission de positons et détection en coïncidence (TEDC) et recalage d'images de simulation virtuelle par tomodensitométrie. Impact sur la planification de la radiothérapie conformationnelle des cancers bronchiques non à petites cellules.

UNLABELLED: To report a retrospective study concerning the impact of fused 18F-fluorodeoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on three-dimensional conformal radiation therapy (3D-CRT) planning for patients with non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: One hundred and one patients consecutively treated for stages I-III NSCLC were studied. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same radiation treatment position. Images were coregistered using five fiducial markers. Target volume delineation was initially performed on the CT images and the corresponding FDG-PET data were subsequently used as an overlay to the CT data to define target volume. RESULTS: FDG-PET identified previously undetected distant metastatic disease in 8 patients making them ineligible for curative CRT (one patient presented some positive uptakes corresponding to concomitant pulmonary tuberculosis). Another patient was ineligible for curative treatment because fused CT/PET images demonstrated excessively extensive intrathoracic disease. The gross tumor volume (GTV) was decreased by CT/PET image fusion in 21 patients (23%) and was increased in 24 patients (26%). The GTV reduction was > or = 25% in 7 patients because CT/PET image fusion reduced pulmonary GTV in 6 patients (3 patients with atelectasis) and mediastinal nodal GTV in 1 patient. The GTV increase was > or = 25% in 14 patients due to an increase of the pulmonary GTV in 11 patients (4 patients with atelectasis) and detection of occult mediastinal lymph node involvement in 3 patients. Among 81 patients receiving a total dose > or = 60 Gy at ICRU point, after CT/PET image fusion, the percentage of total lung volume receiving more than 20 Gy (VL20) increased in 15 cases and decreased in 22 cases. The percentage of total heart volume receiving more than 36 Gy increased in 8 patients and decreased in 14 patients. The spinal cord volume receiving at least 45 Gy (2 patients) decreased. After multivariate analysis, one single independent factor made significant effect of FDG/PET on the modification of the size of the GTV: tumor with atelectasis (P = 0.0001). Conclusion. - Our study confirms that integrated hybrid PET/CT in the treatment position and coregistered images have an impact on treatment planning and management of patients with NSCLC. FDG images using dedicated PET scanners with modern image fusion techniques and respiration-gated acquisition protocols could improve CT/PET image coregistration. However, prospective studies with histological correlation are necessary and the impact on treatment outcome remains to be demonstrated.

[Impact of computed tomography (CT) and 18F-deoxyglucose positron emission tomography (FDG-PET) image fusion for conformal radiotherapy in esophageal carcinoma]. / Tomographie par émission de positons et fusion d'images de simulation virtuelle par tomodensitométrie. Impact sur la planification de la radiothérapie conformationnelle des cancers de l'oesophage.

PURPOSE: To study the impact of fused (18)F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on conformal radiation therapy (CRT) planning for patients with esophageal carcinoma. PATIENTS AND METHODS: Thirty-four patients with esophageal carcinoma were referred for concomitant radiotherapy and chemotherapy with radical intent. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same radiation treatment position. PET-images were coregistered using five fiducial markers. Target delineation was initially performed on CT images and the corresponding PET data were subsequently used as an overlay to CT data to define the target volume. RESULTS: FDG-PET identified previously undetected distant metastatic disease in 2 patients, making them ineligible for curative CRT. The Gross Tumor Volume (GTV) was decreased by CT and FDG image fusion in 12 patients (35%) and was increased in 7 patients (20.5%). The GTV reduction was >or=25% in 4 patients due to reduction of the length of the esophageal tumor. The GTV increase was >or=25% with FDG-PET in 2 patients due to the detection of occult mediastinal lymph node involvement in one patient and an increased length of the esophageal tumor in the other patient. Modifications of the GTV affected the planning treatment volume (PTV) in 18 patients. Modifications of delineation of GTV and displacement of the isocenter of PTV by FDG-PET also affected the percentage of total lung volume receiving more than 20 Gy (VL20) in 25 patients (74%), with a dose reduction in 12 patients and a dose increase in 13 patients. CONCLUSION: In our study, CT and FDG-PET image fusion appeared to have an impact on treatment planning and management of patients with esophageal carcinoma related to modifications of GTV. The impact on treatment outcome remains to be demonstrated.

[Role of [18F]-fluorodeoxyglucose positron emission tomography for the initial detection, staging, search for recurrences and restaging of gynaecological and breast cancers]. / Intérêt de la tomographie par émission de positons au [18F]-fluorodésoxyglucose dans le diagnostic, le bilan d'extension et la recherche de récidive des cancers gynécologiques et mammaires.

Positron emission tomography (PET) using fluorodeoxyglucose (FDG) is a new metabolic imaging modality that is becoming accessible in France. Many centers have been or will be equipped soon. The indications of PET-FDG have been established in various settings in some oncology pathologies such as lymphoma or lung cancer, but not in gynaecological and breast cancers. Therefore, we aimed to precise the interest of PET-FDG to detect, stage and restage the cancers of breast, ovary, cervix and uterus by reviewing the recent publications.

[Results of FDG-PET scanning in the pre-operative staging of broncho-pulmonary tumors]. / Résultats de la TEP [18F]-FDG dans la stadification préopératoire des tumeurs pulmonaires.

BACKGROUND: Positron emission tomography (PET) with [18F]fluorodeoxyglucose (FDG) has recently established itself as an important imaging strategy in the management of respectable non-small cell bronchial carcinoma (NSCLC). In this study we report our experience of the impact of FDG-PET in the pre-operative assessment of NSCLC. METHODS: In a single centre retrospective study between 01 January 2000 and 31 Dec 2002, 108 FDGPET scans were performed during the preoperative assessment of histologically proven or strongly suspected NSCLC. RESULTS: The sensitivity, specificity and accuracy of FDG-PET for the characterization of a parenchymatous opacity were 96%, 71% and 92% respectively (4 false negatives, 5 false positives). The sensitivity, specificity and accuracy for mediastinal node involvement were 62%, 94% and 84% respectively (10 false negatives and 4 false positives). The sensitivity, specificity and accuracy for the characterization of adrenal nodules were 88%, 100% and 97% (1 false negative) and for satellite pulmonary nodules 50%, 75% and 64% (2 false negatives and 3 false positives). CONCLUSION: FDG-PET is a useful imaging modality in the pre-operative management of NSCLC but is limited particularly in the characterization of lesions less than 10 mm in diameter and in the evaluation of mediastinal lymph nodes.

Current applications of PET imaging of sex hormone receptors with a fluorinated analogue of estradiol or of testosterone.

Currently, the most frequent approach in the oncologic applications of positron emission tomography (PET) is detecting the hypermetabolic activity of the cancer tissue. A more specific approach, which may be complementary, is detecting the overexpression of receptors. In this review article, we aim to evaluate the results that are currently available for PET imaging of the sex hormone receptors in clinical oncology. The indication of PET and now PET/CT has been more disputed in breast carcinoma than in many other primary cancers (e.g., lung, head and neck, colorectal, lymphoma). 18F-fluorodeoxyglucose (FDG), the glucose analogue for PET imaging, has a limited sensitivity to detect the primary breast tumors in case of lobular or in situ forms or small sized tumors localised on systematic mammography, and to identify minimal node invasion in the axilla. Using 16α-[¹8F]fluoro-17ß-estradiol (FES), a fluorinated estradiol analogue, PET is able to detect the over-expression of the oestrogen receptor (ER) in lesions, at a whole-body level. FES and FDG appear complementary for a better diagnostic performance in staging locally advanced breast cancer or restaging recurrent or metastatic breast cancer. Another potential indication is predicting the response to starting or resuming hormone therapy in patients with metastatic breast cancer, in relation with the ER status of all lesions revealed by FES PET. In two retrospective studies, FDG PET was also able to predict the response to hormone therapy, on basis of a metabolic flare, observed either after 7-10 days of treatment or during an estradiol challenge. A prospective comparison of those approaches is warranted. One study reported predicting response to neoadjuvant chemotherapy thanks to a low value of FES SUV(max) or FES/FDG SUV(max) ratio. The presence of ER in uterine tumors, including the benign ones, in ovarian cancers or even in meningiomas, may have therapeutic consequences and FES PET could have a clinical utility in those settings; only initial results are available. The indication of PET and PET/CT has been even more disputed in prostate carcinoma, due to the lack of significant FDG uptake in most cases, at least before the castration-resistant stage. Using FDHT, a fluorinated testosterone analogue, PET is able to detect the over-expression of the androgen receptor (AR) in lesions, at a whole-body level. At least partly due to the rather large number of alternative tracers that are in development or even routinely available in some countries, few FDHT studies have been published until now. From absorbed dose values previously published for FES by the team of University of Washington School of Medicine at Seattle, and for FDHT by the teams of Memorial Sloan-Kettering Cancer Center at New York and of Washington University at St. Louis, we applied the coefficients of ICRP publication 103 and calculated an effective dose per unit of injected activity of 0.023 mSv/MBq for FES and 0.018 mSv/MBq for FDHT. The radiation exposure is of the same order of magnitude as with FDG.

(68)Ga-AMBA and (18)F-FDG for preclinical PET imaging of breast cancer: effect of tamoxifen treatment on tracer uptake by tumor.

INTRODUCTION: AMBA is a bombesin analogue that binds to GRPr. In a mouse model of estrogen-dependent human breast cancer, we tested whether (68)Ga-AMBA can be used for PET detection of GRPr-expressing tumors and could be more accurate than (18)F-FDG to monitor tumor response to hormone therapy. METHODS: The radiolabeling of (68)Ga-AMBA was automated using a R&D Synchrom module. ZR75-1, a breast cancer cell line, was xenografted in nude mice. (68)Ga-AMBA tumor uptake was compared with that of (18)F-FDG before and after treatment with tamoxifen. RESULTS: AMBA was (68)Ga-radiolabelled in 30min with 95.3% yield and purity≥98%. Prior to treatment, (68)Ga-AMBA was highly concentrated into tumors (tumor to non-tumor ratio=2.4 vs. 1.3 with (18)F-FDG). With tamoxifen treatment (n=6) (68)Ga-AMBA uptake plateaued after 1week and decreased after 2weeks, with a significant reduction compared to controls (n=4). In contrast the effect of tamoxifen treatment could not be appreciated using (18)F-FDG. CONCLUSIONS: (68)Ga-AMBA appeared better than (18)F-FDG to visualize and monitor the response to hormone treatment in this breast cancer model.

[18F]-FDG positron imaging in clinical management of lymphoma patients.

[18F]-FDG is a glucose analogue labelled with a short-lived positron emitter. During the past decade, it has been proposed to detect in vivo lymphoma lesions with PET, a new non-invasive imaging modality. We aimed at reviewing the current experience with FDG in several clinical settings of lymphoma. Due to the lack of specificity of FDG for lymphoma, histology remains compulsory to establish the diagnosis. Nevertheless, in the case of AIDS, FDG imaging has been proposed to differentiate lymphoma and opportunistic infections in brain lesions. To explore lymphoma extension, FDG-PET highlights more lesions than CT or the clinical examination and results in upstaging 13% of cases. It could also be used for selecting a site for biopsy when the location considered first clinically is difficult to access. Staging lymphoma with FDG-PET also provides baseline images for subsequent evaluation of therapy, which is one of the most promising indications: a negative scan predicts response to therapy and subsequent remission with a predictive value of 89%, and a positive scan either reflects resistance or predicts relapse with a predictive value of 83%. The current achievement of FDG imaging is the early detection of recurrence or of viable tissue in residual masses that remain several months after treatment. Both its sensitivity (84%) and its specificity (95%) overwhelm the values of conventional imaging, mainly CT and gallium-67 scintigraphy. When PET, as a new clinical imaging modality, is not yet widely demanded by clinicians and/or the number of FDG examinations is less than 500 per year, a 'hybrid' gamma-camera or CDET can be an alternative to dedicated PET. For 3 years, we have been using FDG-CDET in the 2D mode without attenuation correction, and obtained the following accuracy in a total of 40 examinations that could be evaluated: 85% for assessment of chemotherapy and 92% to detect recurrences and evaluate residual masses. Our preliminary results also stress the interest in FDG examination in childhood lymphoma, with the same indications as in adults.

CT and (18)F-deoxyglucose (FDG) image fusion for optimization of conformal radiotherapy of lung cancers.

PURPOSE: To validate a computed tomography (CT) and (18)F-deoxyglucose (FDG) image fusion procedure and to evaluate its usefulness to facilitate target definition and treatment planning in three-dimensional conformal radiation therapy (3D-CRT) for non-small-cell lung cancer. METHODS AND MATERIALS: Twelve patients were assessed by CT and FDG-coincidence mode dual-head gamma camera (CDET) before radiotherapy. The patients were placed in a similar position during CT and FDG-CDET. Matching was achieved by minimizing the cost function by 3D translation and rotation between four landmarks drawn on the patient's skin. Virtual simulation was performed from image fusion and estimated dose-volume histograms (DVH) were calculated. RESULTS: Quantitative analysis indicated that the matching error was < 5 mm. Fusion of anatomic and metabolic data corrected staging of lymph nodes (N) for 4 patients and staging of metastases for 1 patient. In these 5 patients, DVH revealed that the lung volume irradiated at 20 Gy (Vl(20)) was decreased by an average of 22.8%, and tumor volume irradiated at the 95% isodose (V(95)) was increased by 22% and 8% for 2 patients, respectively, and was decreased by an average of 59% for 3 patients after fusion. No difference in terms of Vl(20) and V(95) was observed for the other 7 patients. CONCLUSION: We have validated CT and FDG-CDET lung image fusion to facilitate determination of lung cancer volumes, which improved the accuracy of 3D-CRT.

Evaluation of FDG uptake by renal malignancies (primary tumor or metastases) using a coincidence detection gamma camera.

UNLABELLED: The aim of this study was to evaluate the usefulness of FDG scanning using an ordinary gamma camera equipped with coincidence detection (CDET) for 2 renal cancer indications: characterization and staging of renal masses before nephrectomy and search for recurrence after nephrectomy. METHODS: Between September 1997 and June 1998, a whole-body scan and at least 1 tomoscintigram were obtained on 23 occasions in 22 patients (fasting for at least 6 h) using a Prism XP 2000 CDET gamma camera; scanning was begun 45 min after intravenous injection of 150-250 MBq FDG. RESULTS: Postoperative histologic evidence was obtained from 13 of 16 patients who underwent FDG using a CDET gamma camera before renal surgery; 4 renal masses did not accumulate FDG (3 true-negatives, 1 false-negative), whereas 9 renal tumors accumulated FDG (8 true-positives, 1 false-positive). In the other 3 patients, only 1 extrarenal site of FDG uptake was checked and confirmed on histologic examination: a bone metastasis from renal cell carcinoma in 2 cases and lymph node metastasis from a squamous cell carcinoma (3 true-positives). The primary local and regional staging of the malignant renal tumors was accurate in the 9 patients who underwent nephrectomy (8 true-negatives, 1 true-positive). The primary distant staging was positive in 1 case (focus in the chest corresponding to a probable true-positive on follow-up). In the 7 examinations performed because of suspected recurrence of renal cell carcinoma several months after nephrectomy, metastases were visualized by FDG in 4 patients, confirmed by biopsy in 2 patients, and confirmed by conventional imaging or follow-up (or both) in 2 patients. The other 3 patients had negative FDG scans, corresponding to probable true-negative results on follow-up. CONCLUSION: FDG using a CDET gamma camera can be used effectively for the staging and restaging of renal tumors and might be useful for characterization of the primary renal tumor in doubtful cases.