Impact of FDG-PET to detect recurrence of head and neck squamous cell carcinoma.

OBJECTIVE: Prospectively evaluate the impact of fluorodeoxyglucose-fluorine-18 positron emission tomography (FDG-PET) in the management of recurrence of advanced head and neck squamous cell carcinoma during the first year after treatment. STUDY DESIGN: Seventy patients were followed-up every 6 to 8 weeks during the first year after initial combined curative therapy. FDG-PET, together with conventional imaging and endoscopy were performed systematically at 1 year (group A) or prompted earlier in case of clinically suspicious recurrence (group B). The referring physician evaluated the impact of FDG-PET on the patient's management. Another clinician checked the pertinence of decisions. RESULTS: FDG-PET had a therapeutic impact in 8 of 43 group A patients and in 16 of 27 group B patients; the overall rate was 34%. This change was pertinent in 5 of 8 and 14 of 16 cases, respectively. Overall pertinence rate of decisions was 90% versus 70% without FDG-PET. CONCLUSIONS: FDG-PET had a significant overall therapeutic impact; the induced decisions were either pertinent or just led to "futile" noninvasive examinations. Systematic FDG-PET had a significantly lesser impact in comparison with FDG-PET motivated by clinical suspicion.

[Clinical usefulness of positron emission tomography in prostate cancer]. / Utilité clinique de la tomographie par émission de positons dans le cancer de la prostate.

In prostate cancer, use of FDG, the radiopharmaceutical currently most widely used in oncology, is limited to the most aggressive cancers and, in the absence of another tracer, to attempting to localise occult recurrences detected biochemically (elevated PSA serum levels). Four other PET tracers are currently suggested in various situations of prostate cancer development: for guiding biopsies, for diagnosis and staging of the primary cancer and of local or metastatic recurrences, especially in bone, and for localizing occult biochemical recurrence. This article is illustrated by cases summarising our experience with fluoromethylcholine-(18F) and PET/CT. They cover a wide spectrum of clinical settings: localisation of intraprostatic neoplastic lesions, initial staging, monitoring treatment by ultrasound, detection of occult recurrences and characterisation of images on conventional imaging modalities, which are questionable or difficult to interpret.

Can fluorodihydroxyphenylalanine PET replace somatostatin receptor scintigraphy in patients with digestive endocrine tumors?

UNLABELLED: The aim of this study was to evaluate whether (18)F-fluorodihydroxyphenylalanine ((18)F-FDOPA) PET is accurate for the diagnosis and follow-up of any type of well-differentiated digestive endocrine tumor and to assess its performance compared with standard somatostatin receptor scintigraphy (SRS) using (111)In-pentetreotide. METHODS: We reviewed the results of 33 evaluable (18)F-FDOPA PET and (111)In-pentetreotide SRS examinations performed between March 2002 and September 2005 in 30 patients referred for documented well-differentiated digestive endocrine tumor. RESULTS: The sensitivity and accuracy of (18)F-FDOPA PET were significantly better for carcinoid tumors (defined according to the World Health Organization 2000 classification) (n = 19) than for noncarcinoid tumors (n = 14)-that is, 93% versus 25% for sensitivity (P < 0.01) and 89% versus 36% for accuracy (P < 0.01), respectively. In contrast, the performances of (111)In-pentetreotide SRS did not differ according to the carcinoid or noncarcinoid type of the primary endocrine tumor-that is, 81% versus 75% for sensitivity and 79% versus 71% for accuracy, respectively. In carcinoid tumors, comparison between (18)F-FDOPA PET and (111)In-pentetreotide SRS showed that (18)F-FDOPA PET more accurately evaluated the extent of disease than (111)In-pentetreotide SRS. (111)In-Pentetreotide SRS did not reveal any additional lesions in any case. Conversely, in noncarcinoid tumors, the extent of the disease was more accurately evaluated in all cases by (111)In-pentetreotide SRS than by (18)F-FDOPA PET. CONCLUSION: This preliminary study emphasizes the importance of a precise histologic characterization of well-differentiated digestive endocrine tumor to select the best radiopharmaceutical. (18)F-FDOPA PET appears to be useful in carcinoid tumors and could become the first-line scintigraphic imaging modality for these tumors, but (111)In-pentetreotide SRS appeared to be a better first-line scintigraphic imaging modality for noncarcinoid digestive tumors.

[FDG PET and its impact on patient's management in oncology]. / L'examen TEP au fluorodésoxyglucose-(18F) et son impact sur la décision thérapeutique en cancérologie.

FDG, a radioactive glucose analog for PET imaging, requires some precautions: it should be used only in patients with glycemia < 7mmol/L, fasting for at least 6 h but well hydrated, and after pregnancy is ruled out. FDG-PET has many indications in oncology. Its clinical utility has been documented in some circumstances, listed as routine indications in the European Principal Characteristics Summary and the French Standards, Options, and Recommendations. The European "Points to Consider" define as a principal criterion of clinical utility the impact of the imaging results on patient management. The original results presented here evaluate the clinical impact of FDG-PET among patients at Tenon Hospital by the rate of modifications in patient' management, determined with the same questionnaire as that used in two California studies of 2044 patients. Our response rate was lower than in our previous retrospective study in 2000 (34% versus 73%), probably because a prospective evaluation requires more work by the referring physician (who had to respond to two separate letters). On the other hand, the modification rate rose significantly (54% versus 46%, p<0.001), especially for colorectal cancer (58% versus 44%, p<0.02). The California studies had similar response rates (31%-48%, depending on the indication). Their modification rates were also similar, although higher for lymphoma (68%), colorectal (65%) and breast (58%) cancers.

[PET and malignant cerebral tumors]. / La TEP dans les tumeurs malignes cérébrales.

Normal biodistribution of FDG includes intense physiologic uptake in the brain, which consumes glucose. The high background therefore makes it difficult to detect the foci taking up glucose, which correspond to malignant lesions. FDG PET is nevertheless clinically useful for detecting high-grade gliomas, cerebral lymphomas and, in some cases, unexpected brain metastases in whole-body PET examinations. As an adjunct to CT and MRI, FDG-PET can make stereotactic radiosurgery more precise in targeting primary or secondary brain cancers and can differentiate necrotic fibrosis from viable cancer tissue during follow-up in cases of abnormal or equivocal MRI results. When available, methionine-(11C) PET delineates low grade gliomas accurately. Several fluorine (18F)-labeled radiopharmaceuticals have been proposed in this setting, with FET and FDOPA apparently the most effective. Four original clinical cases illustrating performances of FET and FDOPA PET in this setting are presented.

[PET in head and neck cancers]. / La TEP dans les cancers des voies aérodigestives supérieures.

FDG PET is useful when cancer in the head or neck (except for tumors of the salivary glands, which cannot be characterized accurately) is diagnosed or suspected but not confirmed by biopsy. It can, for example, find evidence of suspicious lymph nodes in clinically N0 necks, detect foci suggestive of distant metastases or second cancers, and provide useful prognostic information. Because it can be very difficult to identify anatomical structures and landmarks on PET images in the head and neck region, PET/CT fusion is very helpful in this area. In early assessment of chemotherapy, the absence of a significant reduction in FDG uptake after one or two cycles predicts lack of efficacy and thus indicates the need to modify the regimen. Conversely, the disappearance of FDG foci indicates effective treatment and good prognosis but cannot rule out the persistence of any malignant tissue at the end of treatment, especially neoadjuvant. Diagnostic impact is probably greatest in monitoring for recurrence and restaging known recurrence: FDG PET should be performed - perhaps routinely - early enough that curative options are still open, but long enough after the end of treatment to avoid false positive results from inflammation. The strategy and timing of FDG PET during follow-up should be determined in more detail in the future, as should the role (if any) of fluorotyrosine (FET) PET in squamous cell carcinoma.

[FDG-PET in localization of cancers of unknown primary origin]. / Place de la TEP au FDG dans la localisation des cancers de primitif inconnu.

FDG-PET can be successful in localizing the primary cancer when a metastasis is discovered but no primary tumor can be identified (cancer of unknown primary, or CUP) by physical examination, laboratory testing (for tumor markers, for example) or conventional imaging. The greatest number of PET studies in CUP concern secondary lesions in cervical lymph nodes, and PET is an established clinical use (highest ranking, 1A) according to the 3rd German Consensus Conference and an "option" in the French Standards, Options, and Recommendations. Success rates range from 30% to 50% in most studies using PET; a higher rate was reported recently with PET/CT. FDG-PET should be performed sufficiently early in cases of neurological paraneoplastic syndrome, because established lesions become irreversible. Identification of the antibody present helps to specify the organ and FDG-PET can then localize the lesion; together these techniques make it possible to perform curative surgery even when the primary tumor is not visible. The success rate is somewhat lower than in cases of metastasis, around 35%. The clinical utility of PET in other paraneoplastic syndromes has not yet been sufficiently studied, but these conditions are rare. It is precisely in cases with a kind of 'orphan' indication that FDG PET should be considered, as an effective "problem solver".

[PET in primary pulmonary or pleural cancer]. / La TEP dans les cancers bronchopulmonaires ou pleuraux primitifs.

In our hospital as in many others, primary lung cancer is the most frequent indication for FDG PET. Studies have assessed the clinical utility of this imaging modality in characterizing solitary pulmonary nodules or masses, initial staging, defining tumor volume in radiotherapy and searching for recurrence of or restaging non-small cell carcinoma; studies are currently underway to evaluate its use in early assessment of chemotherapy response. Small cell lung cancer has a high FDG uptake and PET/CT can be useful for rapid staging. False negative results may be due to pure bronchioloalveolar carcinomas and endocrine tumors. FDG-PET will certainly play a more important role in the diagnosis and follow-up of pleural cancers in the future. An unexpected positive FDG PET focus should be considered as a warning, but histological proof should precede any irrevocable decisions.

[PET in thyroid cancers]. / La TEP dans le cancer de la glande thyroïde.

FDG PET can detect thyroid cancer in patients referred for exploration of a different cancer. Because of its lack of specificity, however, this modality is not indicated for examination of thyroid nodules: ultrasonography and fine needle biopsy with cytology allow histological diagnosis, which can be completed by iodine-123 scintigraphy when an autonomous nodule is suspected. No information is currently available about the utility of FDG PET in preoperative staging. In follow-up of patients undergoing thyroidectomy for adenocarcinoma, FDG PET is useful for detecting recurrence in cases where serum thyroglobulin levels rise and iodine-131 scintigraphy is negative: surgical resection may be appropriate. Nonetheless FDG PET should be performed more widely and earlier: the initial presence of foci positive for FDG is a major predictor of shorter survival, and most cancer lesions take up either iodine or FDG. In follow-up of medullary carcinoma, FDG PET detects residual tissue better than any other scintigraphic procedures, especially when serum levels of CEA (carcinoembryonic antigen) are rising rapidly. FDOPA PET seems to have better sensitivity than FDG-PET and may be useful in occult recurrence, as three case reports indicate.

Impact of computed tomography and 18F-deoxyglucose coincidence detection emission tomography image fusion for optimization of conformal radiotherapy in non-small-cell lung cancer.

PURPOSE: To report a retrospective study concerning the impact of fused 18F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and CT images on three-dimensional conformal radiotherapy planning for patients with non-small-cell lung cancer. METHODS AND MATERIALS: A total of 101 patients consecutively treated for Stage I-III non-small-cell lung cancer were studied. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same 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 the target volume. RESULTS: 18F-fluoro-deoxy-D-glucose-PET identified previously undetected distant metastatic disease in 8 patients, making them ineligible for curative conformal radiotherapy (1 patient presented with some positive uptake corresponding to concomitant pulmonary tuberculosis). Another patient was ineligible for curative treatment because the fused PET-CT 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 the pulmonary GTV in 6 patients (3 patients with atelectasis) and the mediastinal nodal GTV in 1 patient. The GTV increase was > or = 25% in 14 patients owing to an increase in the pulmonary GTV in 11 patients (4 patients with atelectasis) and detection of occult mediastinal lymph node involvement in 3 patients. Of 81 patients receiving a total dose of > or = 60 Gy at the International Commission on Radiation Units and Measurements point, after CT-PET image fusion, the percentage of total lung volume receiving >20 Gy increased in 15 cases and decreased in 22. The percentage of total heart volume receiving >36 Gy increased in 8 patients and decreased in 14. The spinal cord volume receiving at least 45 Gy (2 patients) decreased. Multivariate analysis showed that tumor with atelectasis was the single independent factor that resulted in a significant effect on the modification of the size of the GTV by FDG-PET: tumor with atelectasis (with vs. without atelectasis, p = 0.0001). CONCLUSION: The results of our study have confirmed that integrated hybrid PET/CT in the treatment position and coregistered images have an impact on treatment planning and management of non-small-cell lung cancer. However, FDG images using dedicated PET scanners and respiration-gated acquisition protocols could improve the PET-CT image coregistration. Furthermore, the impact on treatment outcome remains to be demonstrated.

Impact of CT and 18F-deoxyglucose positron emission tomography image fusion for conformal radiotherapy in esophageal carcinoma.

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 radiotherapy planning for esophageal carcinoma patients. METHODS AND MATERIALS: Thirty-four esophageal carcinoma patients were referred for concomitant radiotherapy and chemotherapy with radical intent. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same 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: (18)F-fluorodeoxy-D-glucose-PET identified previously undetected distant metastatic disease in 2 patients, making them ineligible for curative conformal radiotherapy. The gross tumor volume (GTV) was decreased by CT and FDG image fusion in 12 patients (35%) and increased in 7 patients (21%). The GTV reduction was > or =25% in 4 patients owing to a reduction in the length of the esophageal tumor. The GTV increase was > or =25% with FDG-PET in 2 patients owing to the detection of occult mediastinal lymph node involvement in 1 patient and an increased length of the esophageal tumor in 1 patient. Modifications of the GTV affected the planning treatment volume in 18 patients. Modifications of the delineation of the GTV and displacement of the isocenter of the planning treatment volume by FDG-PET also affected the percentage of total lung volume receiving >20 Gy in 25 patients (74%), with a dose reduction in 12 patients and dose increase in 13. CONCLUSION: In our study, CT and FDG-PET image fusion appeared to have an impact on treatment planning and management of esophageal carcinoma. The affect on treatment outcome remains to be demonstrated.

6-[F-18]fluoro-L-DOPA positron emission tomography in the imaging of Merkel cell carcinoma: preliminary report of three cases with 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography or pentetreotide-(111In) SPECT data.

PURPOSE: Merkel cell carcinoma (MCC) is an uncommon and aggressive cutaneous neoplasm of neuroendocrine origin. Somatostatin receptor scintigraphy (SRS) and positron emission tomography (PET) using 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) have been proposed to stage MCC and to detect early recurrences. As 6-[F-18]fluoro-L-DOPA (FDOPA) is taken up by other neuroendocrine tumors, we speculated that FDOPA-PET could image MCC. PROCEDURE: FDOPA-PET was performed together with FDG-PET (three patients) and SRS (two patients) in different clinical settings: localization of the primary tumor, staging, and suspicion of recurrence. RESULTS: Uptake of FDOPA-(18F) by MCC was observed in the two true-positive cases, with an agreement between the results of FDOPA-PET, FDG-PET, and SRS; however, the contrast was lower on FDOPA-PET than on FDG-PET images. In the last patient suspected of recurrence repeatedly on SRS and with inconclusive FDG-PET, FDOPA-PET was negative, and a 12-month follow-up demonstrated a true-negative result. CONCLUSION: MCC takes up FDOPA-(18F). The potential role of FDOPA-PET in its management warrants clarification.

Detection of recurrent colorectal carcinoma by 18F-FDG: comparison of the clinical performances of FDG PET and FDG CDET.

OBJECTIVES: To assess the clinical performance of fluorodeoxyglucose positron emission tomography (FDG PET) using either a coincidence (CDET) gamma camera or PET equipment with Nal crystals for the detection of recurrences of colorectal cancer. METHODS: From July 1997 to December 1999, 290 examinations were performed in 244 patients using a CDET gamma camera (2-dimensional system with 19 mm thick crystals). Additionally, from January 2000 to July 2002, 354 examinations were performed in 303 patients using PET (3-dimensional system with Nal crystals). RESULTS: Four hundred and seventy-three of the 644 examinations performed were evaluable on the basis of histological data (202 examinations) or more than 6 months of follow-up (273 examinations). The performances of the two systems were equivalent on a patient basis (sensitivity, specificity and accuracy of dedicated PET was 92%, 84% and 90%, respectively; and sensitivity, specificity and accuracy of CDET was 90%, 94% and 91%, respectively). On a site basis, a highly significant reduction in sensitivity was observed for lesions < or = 10 mm vs. > 10 mm with both PET and the CDET gamma camera, but no difference was observed between PET and CDET according to the size of the lesions. CONCLUSION: For detection of recurrent colorectal carcinoma, a 2-D coincidence gamma camera with 19 mm thick crystals and optimized acquisition and reconstruction parameters provides similar results in terms of accuracy, both per patient and per site, to those of an Nal PET camera.

Added value of early 18F-FDOPA PET/CT acquisition time in medullary thyroid cancer.

The aim of this study was to determine whether early acquisition of F-fluorodihydroxyphenylalanine (F-FDOPA) PET/CT could improve the detection of medullary thyroid cancer (MTC). We retrospectively compared early (median time: 15 min) and delayed (median time: 94 min) acquisitions, positive on at least one of the two phases, in 15 dual-phase F-FDOPA PET/CT examinations performed on 14 patients referred for initial staging (one examination), suspected recurrence (eight examinations) or restaging of MTC (six examinations). Among the 14 true-positive (TP) examinations, more lesions (51 vs. 43) or more intense uptake (mean SUVmax=4 vs. 2.4, P<0.05) was observed on early versus delayed phases, regardless of the anatomical site of disease (lymph node, liver or bone). The only false-positive case, a reactive lymph node, was visible only on the delayed acquisition. Early acquisition appeared to be more appropriate in the detection of MTC lesions compared with acquisition at 60 min or later.

[PET and digestive cancers]. / Tomographie par émission de positons et cancers digestifs.

In digestive oncology, the most frequent indication for FDG PET, in our experience and as reported in the literature, is the localisation of recurrent colorectal cancer. This molecular imaging method has also been shown to be clinically useful in various other settings, especially for preoperative staging, for colorectal, esophageal, gastric, pancreatic, hepatic and biliary cancers. We also report on current PET practice in two particular cancers: hepatocellular carcinoma, for which other tracers, including fluoromethylcholine-(18F), are being currently evaluated, and gastrointestinal endocrine tumours, which are included in the recent French marketing authorisation of fluoroDOPA-(18F) and which are also potential targets for radiolabelled somatostatin analogues for PET imaging.

PET/CT in patients with hepatocellular carcinoma using [(18)F]fluorocholine: preliminary comparison with [(18)F]FDG PET/CT.

PURPOSE: The diagnostic accuracy of [(18)F]fluorodeoxyglucose (FDG) PET is insufficient to characterise hepatocellular carcinoma (HCC) in liver masses and to diagnose all cases of recurrent HCC. HCC has been reported to take up [(11)C]acetate, but routine use of this tracer is difficult. Choline is another tracer of lipid metabolism, present in large amounts in HCC. In a proof-of-concept study, we evaluated [(18)F]fluorocholine (FCH) uptake by HCC and compared FCH PET/CT with FDG PET/CT. METHODS: Twelve patients with newly diagnosed (n=8) or recurrent HCC (n=4) were prospectively enrolled. HCC was assessed by histology in eight cases and by American Association for the Study of Liver Diseases (AASLD) criteria in four cases. All patients underwent whole-body PET/CT 10 min after injection of 4 MBq/kg FCH. Within 1 week, 9 of the 12 patients also underwent whole-body FDG PET/CT 1 h after injection of 5 MBq/kg FDG. RESULTS: The per-patient analysis showed a detection rate of 12/12 using FCH PET/CT for both newly diagnosed and recurrent HCC. The median signal to noise ratio was 1.5+/-0.38. There was a trend towards a higher FCH SUV(max) in well-differentiated HCC (15.6+/-7.9 vs 11.9+/-0.9, NS). Of the nine patients who underwent FCH and FDG PET/CT, all nine were positive with FCH whereas only five were positive with FDG. CONCLUSION: FCH provides a high detection rate for HCC, making it potentially useful in the initial evaluation of HCC or in the detection of recurrent disease. The favourable result of this proof-of-concept study opens the way to a phase III prospective study.