Detection Of Unknown Primary Tumours Research Articles

Pivotal role of PET/CT in characterization of occult metastasis with undetermined origin

BackgroundThe purpose of this multicenter diagnostic accuracy test study was conducted to assess the role of positron emission tomography/computed tomography in the detection of primary tumor in cases of metastasis of undetermined primary site, to estimate its capability in detecting additional lesions as well as evaluating disease burden and staging. This multicentric diagnostic accuracy test study included 175 patients with pathologically proven, radiologically, and/or clinically suspected metastatic lesions of undetermined primary site. Clinical, surgical, and histopathologic findings and correlative imaging modalities were used to assess the results of PET/CT; the accuracy of PET/CT was expressed in terms of sensitivity and specificity, positive and negative predictive values.ResultsThe study included 175 patients; PET-CT-positive lesions suggestive of primary malignant tumors were detected in 105 out of 175 patients. These lesions were pathologically proven to be malignant (true positive) in 100/175 patients (57.1%). Five out of 175 patients (2.9%) proved to be falsely positive after pathologic assessment; 70 out of 175 patients (40%) were negative for detection of primary malignancy all over the body by PET/CT (true negative) with no false negative results. PET/CT achieved a sensitivity of 100%, and specificity of 93.3% in detection of unknown primary tumor location.ConclusionPET/CT is an effective modality for early detection of the primary tumor site in patients with cancer of undetermined primary (CUP) which facilitates early selection of appropriate treatment protocols that will improve patients’ prognosis.

The Additional Value of Ultrafast DCE-MRI to DWI-MRI and 18F-FDG-PET to Detect Occult Primary Head and Neck Squamous Cell Carcinoma.

Simple SummaryPatients with cervical lymph node metastasis from squamous cell carcinoma undergo extensive irradiation or surgery of the head and neck with higher treatment morbidity, recurrence rate and lower overall survival than patients with overt primary tumor. In order to enhance treatment efficiency and morbidity reduction, the primary tumor detection accuracy was evaluated by using Ultrafast-Dynamic Contrast-Enhancement (DCE-)MRI in addition to Diffusion-Weighted (DW-)MRI and 18F-FDG-PET/CT imaging. Ultrafast-DCE, with a temporal resolution of 4 s, enabled capturing lesions with increased neoangiogenesis or perfusion compared to normal tissue. The use of Ultra-fast DCE resulted in higher confidence for suspicious locations and high observer agreement. Ultrafast-DCE showed potential to improve detection of unknown primary tumors in addition to DWI and 18F-FDG-PET/CT in patients with cervical squamous cell carcinoma lymph node metastasis. The combined use of ultrafast-DCE, DWI and 18F-FDG-PET/CT yielded highest sensitivity.To evaluate diagnostic accuracy of qualitative analysis and interobserver agreement of single ultrafast-DCE, DWI or 18F-FDG-PET and the combination of modalities for the detection of unknown primary tumor (UPT) in patients presenting with cervical lymph node metastasis from squamous cell carcinoma (SCC). Between 2014–2019, patients with histologically proven cervical lymph node metastasis of UPT SCC were prospectively included and underwent DWI, ultrafast-DCE, and 18F-FDG-PET/CT. Qualitative assessment was performed by two observers per modality. Interobserver agreement was calculated using the proportion specific agreement. Diagnostic accuracy of combined use of DWI, ultrafast-DCE and 18F-FDG-PET/CT was assessed. Twenty-nine patients were included (20 males. [68%], median age 60 years). Nine (31%) primary tumors remained occult. Ultrafast-DCE added reader confidence for suspicious locations (one additional true positive (5%), 2 decisive true malignant (10%). The per-location analysis showed highest specific positive agreement for ultrafast-DCE (77.6%). The per-location rating showed highest sensitivity (95%, 95%CI = 75.1–99.9, YI = 0.814) when either one of all modalities was scored positive, and 97.4% (95%CI = 93.5–99.3, YI = 0.774) specificity when co-detected on all. The per-patient analysis showed highest sensitivity (100%) for 18F-FDG-PET/CT (YI = 0.222) and either DWI or PET (YI = 0.111). Despite highest trends, no significant differences were found. The per-patient analysis showed highest specific positive agreement when co-detected on all modalities (55.6%, 95%CI = 21.2–86.3, YI = 0.456). Ultrafast-DCE showed potential to improve detection of unknown primary tumors in addition to DWI and 18F-FDG-PET/CT in patients with cervical squamous cell carcinoma lymph node metastasis. The combined use of ultrafast-DCE, DWI and 18F-FDG-PET/CT yielded highest sensitivity.

Detection of unknown primary tumor in patients presented with brain metastasis by F-18 fluorodeoxyglucose positron emission tomography/computed tomography.

Aim:F-18 fluorodeoxyglucose (FDG) PET/CT has several advantages in diagnosis of cancer of unknown primary with reported incremental diagnostic value. In this study, we evaluated the patients who were presented with multiple brain metastasis and unknown primary tumor.Materials & methods:31 patients (17 males, 14 females; mean: 56.1 ± 14.22 years old) with diagnosis of brain metastasis according to histopathology and/or MRI were included into this retrospective study.Results:The patients presented with hypermetabolic (n = 17; mean SUVmax: 11.6 ± 6.9) or hypometabolic brain lesions with additional different metastatic sites in 13 patients (mean SUVmax: 9.03 ± 4.02). The primary tumor was determined by FDG PET/CT in 20/26 patients (77%) (lung [n = 6], primary brain [n = 9], renal cell carcinoma [n = 2], skin [n = 1], breast [n = 1] and neuroendocrine tumor [n = 1]).Conclusion:New generation multislice scanners may provide higher detection ratios. The detection rate of FDG PET/CT might be higher than previously reported according to this study.

Clinical study of 99mTc-3P-RGD2 peptide imaging in osteolytic bone metastasis.

ObjectiveTo investigate the value of integrin αvβ3 targeted imaging with 99mTc-HYNIC-PEG4-E[PEG4-c(RGDfk)]2 (99mTc-3P-RGD2) as a radiotracer in dectecting osteolytic bone metastases.MethodsThis is a retrospective study involving a cohort of 69 consecutive patients including 59 with lung cancer and 10 with other cancers. Patients were required to receive whole body scan (WBS) and regional SPECT/CT imaging with 99mTc-3P-RGD2 (RGD imaging) and 99mTc-MDP (MDP imaging) as a radiotracer successively within days. Final diagnosis was based on comprehensive assessment of all available data including case history, CT, MRI, SPECT/CT, PET/CT, histopathology and 6-12 months follow-up. Visual observation and semiquantitative analysis (T/N: tracer uptake ratio of osteolytic metastases to normal bone) of 99mTc-3P-RGD2 or 99mTc-MDP imaging were performed and their detective values for osteolytic metastases were compared.ResultsA total of 131 osteolytic metastatic lesions were retrospectively studied. Osteolytic metastases mainly presented as “hot region”, occasionally as “cool or normal region” on RGD imaging. The detection sensitivity of RGD WBS for osteolytic metastases was significantly higher than that of 99mTc-MDP WBS (80.9% vs. 46.6%, p<0.01). The sensitivity increased to 96.2% (126/131) when combining with SPECT/CT. 99mTc-3P-RGD2 imaging also promoted the detection of unknown primary tumor, lymph node metastases and offered information for clinical staging. T/N of 99mTc-3P-RGD2 in lung adenocarcinoma osteolytic metastases showed no statistical difference compared with that in squamous-cell carcinoma (6.84±3.46 vs. 7.33±3.22, t = 0.39, p = 0.71). Whereas, it was higher in osteolytic metastases from lung cancer than that from thyroid cancer (7.05±3.01 vs. 4.11±2.67, p = 0.03).Conclusion99mTc-3P-RGD2 peptide imaging showed great potential for detection of osteolytic bone metastasis due to high expression level of integrin αvβ3 on osteoclast and most tumor cells.

Impact of FDG-PET/CT for the Detection of Unknown Primary Tumours in Patients with Cervical Lymph Node Metastases

Objective: Because the detection of the primary tumour is of importance to optimize the patient’s management and allows a targeted therapy, the performance of hybrid positron emission tomography–computed tomography (PET/CT) using fluorodeoxyglucose (FDG) in the detection of primary tumors and unrecognized metastases with cervical lymph node metastases were evaluated in a retrospective study. Material and Methods: Twenty patients with cervical lymph node metastases of unknown primary tumors underwent staging with FDG-PET/CT. All underwent head and neck examinations, computed tomography (CT), and/or magnetic resonance imaging (MRI), panendoscopies, and biopsies of head and neck mucosal sites. The diagnostic accuracy of FDG-PET/CT in detecting primary tumors was compared with that of histopathology and clinical follow-up. The ability of FDG-PET/CT to detect distant metastases was also tested. Results: PET/CT was positive with an increased FDG uptake suggesting the potential primary site in 45% of patients (9/20). PET/CT findings were true positive in 7, true negative in 10, false positive in 2, and false negative in 1 patients, resulting in a sensitivity of 87%, a specificity of 83%, an accuracy of 85%, a positive predictive value of 77% and a negative predictive value of 90%. Also, PET/CT showed distant metastases in seven patients. Conclusion: FDG-PET/CT can be successfully used for the identification of the primary site and distant metastases in patients with cervical lymph node metastases from an unknown primary cancer. Conflict of interest:None declared.

The role of PET-CT in detecting unknown primary tumour in patients with cervical lymph node metastases

PET-CT examination was conducted with 440 patients treated at the Department of Head and Neck Surgery, National Institute of Oncology, Budapest, between January 1, 2006 and December 31, 2010. Out of them 77 patients were selected with whom no examination of any sort (physical, pan-endoscopy, or any of the conventional imaging techniques) succeeded in identifying the primary tumour. In each case the primary examination (aspiration cytology and histology) verified cervical metastases, most of them being squamous cell carcinoma. The significance of PET-CT was retrospectively evaluated in cases of unknown primary tumour with verified cervical metastases. We tested the sensitivity of PET-CT in detection of the primary malignant tumour, and possible distant metastases or a second primary in order to plan an optimal treatment schedule for the patient. Patients with whom the examinations specified in the treatment protocol (physical examination, pan-endoscopy, conventional imaging, biopsy) had failed to diagnose the primary tumour were referred to PET-CT. In each case 18F-FDG tracer was used. In 21/77 patients (27%), the PET-CT yielded unequivocal evidence for the primary tumour confirmed by histology, as well. With 10 others (13%), the precarious diagnoses by various imaging techniques were confirmed by the PET-CT. False positive findings with PET-CT that were not verified either by histology or control examination tests occurred but in 10 patients (13%). Concerning the primary tumour, false negative result was obtained only with 3 patients (4%). It should be noted that their retrospective evaluation proved diagnostic errors, the primary tumours were visible in all the scans. With 33 patients (43%) PET-CT furnished no additional information compared to the previous examinations. In 10 patients, asymptomatic distant metastases and in 3 patients synchronous tumours were diagnosed. We also acknowledge that the significance of PET-CT using 18F-FDG is unquestionable in the detection of unknown primary tumours. It is strongly recommended to re-include the detection of unknown primaries in the approved national indication list of PET-CT. (Note, until January 1, 2008 it had been included!) PET-CT is capable of detecting a primary tumour, after all unsuccessful diagnostic examinations till then, in 25-40% of the cases. One cannot disregard the role and significance of PET-CT in the detection of asymptomatic synchronous tumours, or distant metastases. These benefits make PET-CT a suitable tool for the refinement of individually tailored treatment strategies leading to better therapeutic results and more favourable cost-benefit ratio.

CT Mucosal Window Settings: A Novel Approach to Evaluating Early T-Stage Head and Neck Carcinoma

The purpose of this study is to evaluate the CT densities of small head and neck mucosal cancers as a means of deriving a CT mucosal window display of narrower window width and higher window level to better detect and delineate head and neck carcinomas. We retrospectively studied 19 subjects with T1-2 head and neck carcinomas. The density of tumor and adjacent normal mucosa on CT were measured. CT scans for the 19 patients with tumors and 35 subjects without mucosal tumors were anonymized and interpreted by two readers using standard soft-tissue windows and were reviewed again 1 week later with the addition of mucosal windows. The mean (± SD) attenuation of 17 visible tumors was 85.5 ± 18.3 Hounsfield units (HU) and that of the surrounding normal mucosa was 55.3 ± 15.2 HU (p < 0.0001). From our data, we derived guideline mucosal window settings-a window width of 120 HU and a window level of 60 HU. On blinded review, reader A detected 12 tumors with the addition of mucosal windows (sensitivity, 63%; specificity, 82%) and nine tumors on soft-tissue windows alone (sensitivity, 47%; specificity, 94%). Reader B detected nine tumors with use of mucosal windows (sensitivity, 47%; specificity, 71%) and eight tumors on soft-tissue windows alone (sensitivity, 42%; specificity, 74%). Early T-stage tumors have higher CT density than normal mucosa. Their conspicuity can be amplified using display windows with narrower window width and higher window level. The potential clinical applications are for the improved detection of unknown primary tumors and delineation of a known mucosal tumor.

Detection of unknown primary tumours: advantage of PET/CT over conventional imaging in identifying primary lesions

Detection of unknown primary tumours: advantage of PET/CT over conventional imaging in identifying primary lesions

Molekulare Bildgebung neuroendokriner Tumoren mit68Ga-markierten Peptiden (Somatostatinrezeptor-PET/CT)

Die Rezeptor-PET/CT mit 68Ga-markierten Somatostatinanaloga (DOTA-NOC, DOTA-TOC oder DOTA-TATE) ermöglicht die hochsensitive molekulare Bildgebung neuroendokriner Tumoren (NET) aufgrund der Expression von Somatostatinrezeptoren und die Erfassung verschiedener Rezeptorsubtypen. Unsere Ergebnisse bei über 3 000 Untersuchungen zeigen, dass die Rezeptor-PET/CT eine erheblich höhere Nachweisgenauigkeit hat, als die konventionelle Szintigrafie (auch wenn diese in SPECT/CT-Technik erfolgt), und dass eine sehr exakte topografische Zuordnung der Tumorherde möglich ist. Mit der Berechnung von Standardized Uptake Values (SUV) stehen reproduzierbare und untersucherunabhängige Messwerte zur Verfügung, die es ermöglichen, Patienten für die Radiorezeptortherapie zu selektionieren und den Therapieverlauf zu überwachen. Die Rezeptor-PET/CT ist das sensitivstes Verfahren zum Nachweis von unbekannten Primärtumoren (CUP-Syndrom), was insbesondere für die Detektion von Pankreas- und Dünndarm-NET gilt; sie ermöglicht eine Ganzkörperuntersuchung („one stop shop”) zum Staging sowie die Selektion von Patienten zur Radiorezeptortherapie und die Tumornachsorge mit einem patientenfreundlichen Verfahren, das schnell (innerhalb einer Stunde) durchführbar ist und mit geringerer Strahlenexposition als die einer konventionellen Ganzkörper-CT erfolgen kann. Die Verwendung des 68Ge/68Ga-Generators hat sich unter klinischen Bedingungen über mehrere Jahre zuverlässig bewährt. Der effektive Kostenaufwand für 68Ga-markierte Somatostatinanaloga dürfte bei entsprechenden Untersuchungszahlen geringer sein, als der für die bisherige szintigrafische Diagnostik. Die Entwicklung anderer tumorspezifischer Peptide sowie weiterer DOTA- oder NOTA-gekoppelter Radiopharmazeutika eröffnet für die Zukunft neue Perspektiven, die letztendlich dazu führen könnten, dass der 68Ga-Generator für die PET/CT künftig eine ähnlich bedeutende Rolle spielen wird, wie dies für den 99mTc-Generator und die konventionelle Gammakamera seit Jahrzenten der Fall ist.

Combined FDG-PET/CT for the detection of unknown primary tumors: systematic review and meta-analysis

The aim of this study was to systematically review and meta-analyze published data on the diagnostic performance of combined 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in the detection of primary tumors in patients with cancer of unknown primary (CUP). A systematic search for relevant studies was performed of the PubMed/MEDLINE and Embase databases. Methodological quality of the included studies was assessed. Reported detection rates, sensitivities and specificities were meta-analyzed. Subgroup analyses were performed if results of individual studies were heterogeneous. The 11 included studies, comprising a total sample size of 433 patients with CUP, had moderate methodological quality. Overall primary tumor detection rate, pooled sensitivity and specificity of FDG-PET/CT were 37%, 84% (95% CI 78–88%) and 84% (95% CI 78–89%), respectively. Sensitivity was heterogeneous across studies (P = 0.0001), whereas specificity was homogeneous across studies (P = 0.2114). Completeness of diagnostic workup before FDG-PET/CT, location of metastases of unknown primary, administration of CT contrast agents, type of FDG-PET/CT images evaluated and way of FDG-PET/CT review did not significantly influence diagnostic performance. In conclusion, FDG-PET/CT can be a useful method for unknown primary tumor detection. Future studies are required to prove the assumed advantage of FDG-PET/CT over FDG-PET alone and to further explore causes of heterogeneity.

Unusual Abdominal Localization of Cat Scratch Disease Mimicking Malignancy on F-18 FDG PET/CT Examination

Because of its high diagnostic sensitivity in detection of unknown primary tumors, F-18 FDG PET/CT was used in the exploration of a 51-year-old woman presenting with multiple lymphadenopathy of the hepatic hilum and several hepatic and splenic hypodensities on radiologic examinations for which malignancy was suspected. Despite the morphofunctional malignant appearance, both histologic examination and PCR analysis revealed Bartonella henselae infection. Moreover, repeat F-18 FDG PET showed disease regression during focused antibiotic therapy.

Role of fluorodeoxyglucose-PET versus fluorodeoxyglucose-PET/computed tomography in detection of unknown primary tumor: a meta-analysis of the literature

The objectives of this study were to evaluate the diagnostic accuracy of fluorodeoxyglucose (FDG)-PET and FDG-PET/computed tomography (CT) in the detection of primary tumors in patients presenting with carcinoma of unknown primary (CUP) unidentified by conventional workup, and to compare the statistical difference between the FDG-PET and FDG-PET/CT. Twenty-eight studies (involving a total of 910 patients) published between 1990 and 2007 were reviewed. These studies evaluated the role of FDG-PET and FDG-PET/CT in the detection of unknown primary tumors after physical examination and conventional workup failed to detect a primary tumor. Systematic methods were used to identify, select, and evaluate the methodological quality of the studies as well as to summarize the overall findings of sensitivity, specificity, and detection capacity of the primary tumor. The overall sensitivity and specificity of FDG-PET in detecting unknown primary tumors were 0.78 [95% confidence interval (CI): 0.72-0.84)] and 0.79 (95% CI: 0.74-0.83), respectively. Furthermore, FDG-PET detected 28.54% of tumors that were not apparent after CUP failed to be detected by conventional workup. Data were collected on the locations of primary tumors detected by FDG-PET in 17 studies and detected by FDG-PET/CT in seven studies. Tumors from the base of the tongue accounted for 20.7% (six of 29) of all false-positive FDG-PET scans, corresponding to a false-positive rate of 28.6% (six of 29), much higher than tumors from the others. FDG-PET exhibited a lower sensitivity with respect to the tumors at the base of the tongue and tonsils, which was 68.2 and 76.7%, respectively. In the eight studies with 430 patients diagnosed with CUP by FDG-PET/CT, 31.4% (n=135) of primary tumors were detected. The pooled sensitivity and specificity were 0.81 (95% CI: 0.74-0.87) and 0.83 (95% CI: 0.78-0.87), respectively. FDG-PET and FDG-PET/CT can detect primary tumors that went undetected by physical examination and conventional workup. FDG-PET exhibited lower sensitivity with respect to the tumors at the base of the tongue and the tonsils.

O44 Cost-effectiveness of FDG-PET for the detection of unknown primary tumours presenting as a lymph node metastasis in the neck

O44 Cost-effectiveness of FDG-PET for the detection of unknown primary tumours presenting as a lymph node metastasis in the neck

S22 Cost-effectiveness of FDG-PET for the detection of unknown primary tumours presenting as a lymph node metastasis in the neck

S22 Cost-effectiveness of FDG-PET for the detection of unknown primary tumours presenting as a lymph node metastasis in the neck

68Ga-DOTA-Tyr3-Octreotide PET in Neuroendocrine Tumors: Comparison with Somatostatin Receptor Scintigraphy and CT

The aim of this study was to evaluate the diagnostic value of a new somatostatin analog, (68)Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-d-Phe(1)-Tyr(3)-octreotide ((68)Ga-DOTA-TOC), for PET in patients with known or suspected neuroendocrine tumors. PET was compared with conventional scintigraphy and dedicated CT. Eighty-four patients (48 men, 36 women; age range, 28-79 y; mean age +/- SD, 58.2 +/- 12.2 y) were prospectively studied. For analysis, patients were divided into 3 groups: detection of unknown primary tumor in the presence of clinical or biochemical suspicion of neuroendocrine malignancy (n = 13 patients), initial tumor staging (n = 36 patients), and follow-up after therapy (n = 35 patients). Each patient received 100-150 MBq (68)Ga-DOTA-TOC. Imaging results of PET were compared with (99m)Tc-labeled hydrazinonicotinyl-Tyr(3)-octreotide ((99m)Tc-HYNIC-TOC) and (111)In-DOTA-TOC. CT was also performed on every patient using a multidetector scanner. Each imaging modality was interpreted separately by observers who were unaware of imaging findings before comparison with PET. The gold standard for defining true-positive (TP), true-negative (TN), false-positive (FP), and false-negative (FN) results was based on all available histologic, imaging, and follow-up findings. PET was TP in 69 patients, TN in 12 patients, FP in 1 patient, and FN in 2 patients, indicating a sensitivity of 97%, a specificity of 92%, and an accuracy of 96%. The FP finding was caused by enhanced tracer accumulation in the pancreatic head, and the FN results were obtained in patients with a tumor of the gastrointestinal tract displaying liver metastases. (68)Ga-DOTA-TOC showed higher diagnostic efficacy compared with SPECT (TP in 37 patients, TN in 12 patients, FP in 1 patient, and FN in 34 patients) and diagnostic CT (TP in 41 patients, TN in 12 patients, FP in 5 patients, and FN in 26 patients). This difference was of statistical significance (P < 0.001). However, the combined use of PET and CT showed the highest overall accuracy. (68)Ga-DOTA-TOC PET shows a significantly higher detection rate compared with conventional somatostatin receptor scintigraphy and diagnostic CT with clinical impact in a considerable number of patients.

The role of 2‐deoxy‐2‐[F‐18]fluoro‐D‐glucose positron emission tomography in disseminated carcinoma of unknown primary site

The authors conducted a comprehensive review of the efficacy of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography (FDG-PET) in the detection of primary tumors in patients with disseminated carcinoma of unknown primary site. Ten studies (involving a total of 221 patients) tat were published between 1998 and 2006 were reviewed. Each study evaluated the role of FDG-PET in the detection of unknown primary tumors after a conventional diagnostic workup. Although 94% of patients had a single site of metastases, the studies otherwise were very heterogeneous in the studied population, study design, and additional diagnostic workup. In 41% of patients, FDG-PET detected primary tumors that were not apparent after conventional workup. In this group of patients, the overall sensitivity, specificity, and accuracy rates of FDG-PET in detecting unknown primary tumors were 91.9%, 81.9%, and 80.5%, respectively. FDG-PET imaging also led to the detection of previously unrecognized metastases in 37% of patients. Lung cancers represented 59% of the detected tumors. FDG-PET had a notably high false-positive rate (58.3%) in tumors of the lower digestive tract. FDG-PET altered the clinical management in 34.7% of patients. Most of those patients (53%) received specific chemotherapy for lung and pancreatic cancers; whereas 12% received specific therapy for breast, ovarian, and prostate cancers; and 14% underwent surgery with curative intent. FDG-PET was an efficient method for detecting primary tumors that were undetected by other modalities and was sensitive for the detection of previously unrecognized metastases. FDG-PET significantly changed clinical management in approximately one-third of the patients studied.

Role of 18FFDG PET/CT in the Treatment of Head and Neck Cancers: Posttherapy Evaluation and Pitfalls

n the United States, extracranial head and neck carcinomas constitute 2–3% of cancers [1], whereas globally they represent 5.4% of all cancers (unpublished data from summary lecture notes, American Society of Head and Neck Radiology). Most head and neck cancers are squamous cell carcinomas of the larynx, nasopharynx, and oral cavity. Accurate initial staging of head and neck malignancies is critical in establishing the prognosis and in selecting the treatment for these patients. After treatment, the complex anatomy in this region is further complicated by postsurgical or radiation changes with the loss of the imaging landmarks and symmetry and with marked distortion of the normal anatomy, making the distinction between posttherapy changes and recurrence or residual tumor challenging. In these situations and in the detection of unknown primary tumors, distant metastases, and synchronous primary tumors, PET with 18F FDG is a better imaging technique than either CT or MRI [2–5]. PET alone, however, has lower spatial resolution than CT or MRI. Fused PET/CT, described by Beyer et al. [6], combines the anatomic detail provided by CT with 18F FDG PET metabolic information, thereby increasing accuracy in the detection of tumor [7].

The role of fluorodeoxyglucose positron emission tomography in cervical lymph node metastases from an unknown primary tumor

The authors performed a comprehensive review of the efficacy of fluorodeoxyglucose positron emission tomography (FDG-PET) in the detection of primary tumors in patients with cervical metastases from unknown primary tumors. Sixteen studies (involving a total of 302 patients) published between 1994 and 2003 were reviewed. These studies evaluated the role of FDG-PET in the detection of unknown primary tumors after conventional workup. In all studies, conventional workup included either panendoscopy or computed tomographic/magnetic resonance imaging, and in 10 of 16 studies, both of these diagnostic techniques were performed before diagnosis. The overall sensitivity, specificity, and accuracy rates of FDG-PET in detecting unknown primary tumors were 88.3%, 74.9%, and 78.8%, respectively. Furthermore, FDG-PET detected 24.5% of tumors that were not apparent after conventional workup. FDG-PET imaging also led to the detection of previously unrecognized metastases in 27.1% of patients (regional, 15.9%; distant, 11.2%). FDG-PET had notably low specificity and a high false-positive rate (39.3%) in the tonsils. In contrast, the false-positive rates for FDG-PET of the base of tongue and hypopharynx were only 21.4% and 8.3%, respectively. FDG-PET exhibited decreased sensitivity to tumors in the base of tongue (81.5%). The sensitivity of this technique at other sites was 90.5%. FDG-PET detected primary tumors that went undetected by other modalities in approximately 25% of cases and was sensitive in the detection of previously unrecognized regional or distant metastases in 27% of cases. FDG-PET had low specificity for tonsillar tumors and low sensitivity for base-of-tongue malignancies.

The usefulness of fluorine 18-labelled deoxyglucose positron emission tomography in the investigation of patients with cervical lymphadenopathy from an unknown primary tumor.

The usefulness of fluorine 18-labelled deoxyglucose positron emission tomography (PET) in the detection of unknown primary tumor in patients seen with malignant cervical lymphadenopathy thought to arise from a head and neck primary differs in the published reports to date. To assess the role of PET in this scenario in our institution, an audit was performed. The records of 21 patients who met the clinical indication were reviewed. End points were the ability of PET to detect an unknown primary tumor and/or distant metastatic disease. In 8 of the 21 patients, PET detected a potential primary site, although none was unequivocally PET positive. One case was pathologically confirmed. In five patients the potential primary site identified on PET could not be confirmed: two had negative biopsies, and three had no clinical evolution in the PET-suspect area for at least 24 months after the initial study. In the remaining two patients, the potential primary site detected by PET was treated without biopsy. PET detected additional regional and/or distant disease that had not been previously documented in nine cases. PET did not add significantly to the detection of an occult primary tumor in patients who had already been comprehensively evaluated by clinical and radiologic investigations. It was of substantial benefit, however, in detecting unsuspected distant disease in patients with undifferentiated nodal histologic findings and helped in delineating regional disease in patients with N2 disease.

Detection of unknown primary tumours in patients with cerebral metastases using whole-body 18F-flouorodeoxyglucose positron emission tomography.

Identification of the unknown primary tumours in patients presenting with cerebral metastasis is a continued diagnostic challenge. Despite extensive and lengthy diagnostic work-up, the primary tumours will remain obscure in a significant proportion of the patients. The aim of this study was to evaluate the use of whole-body 18-F-fluorodeoxyglucose positron emission tomography (18FDG PET) scanning in this pursuit. Sixteen patients aged 34-74 years, with histologically confirmed metastatic brain tumours, were included in the study. Whole-body 18FDG PET identified pulmonary foci of probable primary tumours in all patients. Subsequent confirmation of tumour tissue was determined either by direct histological verification or indirectly by the observation of lesion appearance or lesion growth on structural imaging. This could only be obtained in eight of 16 patients, all defined as true positive. Of the remaining eight, a biopsy could not be sampled from seven patients, because of death or limited follow-up investigations, and one patient had pulmonary malignant melanoma metastases. Whole-body 18FDG PET scanning is a sensitive tool in the search for unknown primary tumours of patients with confirmed cerebral metastases allowing early and focused histological confirmation from suspicious lesions.