Dual modality of 18F-fluorodeoxyglucose-positron emission tomography/computed tomography in patients with cervical carcinoma of unknown primary

The Added Value of 68Ga-FAPI-04 PET/CT in Patients with Head and Neck Cancer of Unknown Primary with 18F-FDG Negative Findings

¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) plays an important role in locating of primary tumor for patients with head and neck cancer of unknown primary (HNCUP). Nevertheless, it can be challenging to locate the primary malignancy in ¹⁸F-FDG-PET/CT scan in some cases. As ⁶⁸Ga-radiolabeled fibroblast activation protein inhibitor (FAPI) PET/CT has promising results in detecting different tumor entities, our study aimed to evaluate the performance of ⁶⁸Ga-FAPI-PET/CT for detecting the primary tumor in HNCUP patients with negative ¹⁸F-FDG findings. Methods: A total of eighteen patients (16 males and 2 females; median age, 55 years; range, 24-72 years) with negative ¹⁸F-FDG findings were enrolled in this study. All patients underwent ¹⁸F-FDG and ⁶⁸Ga-FAPI-PET/CT within one week. Biopsy and histopathological examinations were done in the sites with positive ⁶⁸Ga-FAPI-PET/CT findings. Results: ⁶⁸Ga-FAPI-PET/CT detected the primary tumor in 7 out of 18 patients (38.89%). Among the 7 patients, in respect of the primary tumor sites, 1 was in nasopharynx, 2 were in palatine tonsil, 2 were in submandibular gland, and 2 were in hypopharynx. The primary tumors showed moderate to intensive uptake of FAPI (mean SUV_max, 8.79; range, 2.60-16.50) and excellent tumor-to-contralateral normal tissue ratio (mean SUV_max ratio, 4.50; range, 2.17-8.21). In lesion-based analysis, a total of 65 lymph nodes and 17 bone metastatic lesions were identified. The mean SUV_max of lymph node metastases were 9.05 ± 5.29 for FDG and 9.08 ± 4.69 for FAPI (P = 0.975); as for bone metastases, the mean SUV_max were 8.11 ± 3.00 for FDG and 6.96 ± 5.87 for FAPI, respectively (P = 0.478). The mean tumor-to-background ratio (TBR) values of lymph node and bone metastases were 10.65 ± 6.59 vs. 12.80 ± 8.11 (P = 0.100) and 9.08 ± 3.35 vs. 9.14 ± 8.40 (P = 0.976), respectively. Conclusion: We presented first evidence of diagnostic role of ⁶⁸Ga-FAPI-PET/CT in HNCUP, and our study demonstrated that ⁶⁸Ga-FAPI-PET/CT had the potential to improve the detection rate of primary tumor in HNCUP patients with negative FDG findings. Moreover, ⁶⁸Ga-FAPI had similar performance in assessing metastases with ¹⁸F-FDG.

Detection efficiency of 18F-flourodeoxyglucose positron emission tomography/computed tomography for primary tumors in patients with carcinoma of unknown primary

Carcinoma of unknown primary (CUP) is defined as biopsy proven tumor metastases that remains unidentified after a thorough diagnostic evaluation. The purpose of this study was to find the detection efficiency of ¹⁸F-flourodeoxyglucose positron emission tomography/computed tomography (¹⁸FDG PET/CT) in patients with CUP. This prospective study was conducted at PET/CT Section of Department of Radiology, Aga Khan University Hospital Karachi, Pakistan from August 2017 to January 2018. Patients with a history of CUP referred for ¹⁸FDG PET/CT scan for detection of primary sites during the study were recruited. ¹⁸FDG PET/CT scan was acquired using standardized protocol, and patients with suspected primary sites underwent biopsies. Scan findings and biopsy results were analyzed to find the detection rate, sensitivity, area under curve (AUC), and positive predictive value (PPV). As no biopsy was performed in negative scan, true negative, and specificity could not be calculated. During the study, 46 consecutive patients with CUP were included. Mean age of cohort was 58 ± 17 years (63% male and 37% female) having a mean body mass index of 24.70 ± 4.97 kg/m². Thirty-four patients (34/46) found to have a hypermetabolic focus suggestive of the primary tumor with known metastatic sites and subjected to biopsy which turned out to be positive in 26/34 patients (true positive). The primary tumor was detected in gastrointestinal and hepatobiliary in 8 (17%), head and neck in 6 (13%), genitourinary 4 (09%), lung 3 (06%), and miscellaneous sites in 5 (11%) patients. Detection rate, sensitivity and PPV of ¹⁸FDG PET/CT were 57%, 68%, and 76%, respectively. Remaining 12/46 patients with negative ¹⁸FDG PET/CT for primary focus did not have biopsy. Receiver operating character curve revealed fair diagnostic strength of ¹⁸FDG PET/CT for detecting unknown primary (AUC 0.667; P = 0.054; standard error = 0.083; confidence interval: 0.504–0.830). We conclude that ¹⁸FDG PET/CT is an effective tool for detecting primary tumor in patients with CUP and its upfront use could preclude the use of many futile diagnostic procedures. Furthermore, higher resolution scanners and acquiring delayed images in patients with negative study could reduce false-negative results in patients with CUP.

Diagnostic and treatment modalities for patients with cervical lymph node metastases of unknown primary site - current status and challenges

Background and Purpose

This review aims to provide a comprehensive overview of the literature and elucidate open questions for future clinical trials concerning diagnostics and treatment modalities for cervical cancer of unknown primary (CUP).

Methods

A literature search for head and neck CUP was performed with focus on diagnostics and therapies as well as molecular markers.

Results

High level evidence on CUP is limited. However, it seems that a consensus exists regarding the optimal diagnostic procedures. The correct implementation of biomarkers for patient stratification and treatment remains unclear. An even greater dispute dominates about the ideal treatment with publications ranging from sole surgery to surgery with postoperative bilateral radiotherapy with inclusion of the mucosa and concomitant chemotherapy.

Conclusions

Cervical CUP represents a very heterogeneous malignant disease. On this account many aspects concerning treatment optimization remain unclear, despite a considerable number of publications in the past. Future research in form of prospective randomized trials is needed in order to better define patient stratification criteria and enable tailored treatment.

Neck lymph node metastases from unknown primary

Metastatic cervical carcinoma from unknown primary is a metastatic disease in the lymph nodes of the neck without any evidence of a primary tumour after appropriate investigation. The condition is rare and definite evidence is lacking for both diagnosis and treatment. In this review of the literature, we tried to draw some clinical indications based on the few available studies. We ultimately came to the following conclusions: (1) a thorough and accurate diagnostic work-up should be systematically offered. It includes accurate inspection with fibroscopy, CT or MRI, fine needle aspiration, panendoscopy and positron emission tomography, (2) Patients with low-volume neck disease, N1 and N2a stage and without extracapsular extension on histopathological examination should receive single modality treatment. Radiotherapy and surgery may be similarly effective but, if possible, surgery (excisional biopsy, neck dissection and tonsillectomy) should be favoured because it consents a more precise staging, (3) patients with more advanced conditions require combined treatment in the form of either resection followed by adjuvant radiation (±chemotherapy) or primary chemoradiation (±post-therapy neck dissection).

Impact of 3T multiparametric MRI and FDG-PET-CT in the evaluation of occult primary cancer with cervical node metastasis

Background

This study aimed to determine the ability of multimodal evaluation with multiparametric 3T-MRI (MPMRI) and positron emission tomography - computed tomography (PET/CT) to detect cancer of unknown primary origin (CUP) with neck lymph node (LN) metastasis.

Methods

The study group comprised 38 retrospectively analysed consecutive patients with LN metastasis in the head and neck (HN) region without known primary tumours (PTs). Statistical values of 3T-MRI and of FDG-PET/CT scans were evaluated.

Results

Of the 38 CUPs, conventional native T1-, T2-weighted and STIR sequences detected 6 PTs. Native sequences plus diffusion-weighted imaging (DWI) found 14-, and with fat suppression contrast-enhanced T1-weighted measurement as well as with the complex MPMRI found 15 primaries and with PET/CT 17 CUPs could be evaluated, respectively. The detection rates were 15.8, 36.8, 39.5, 39.5 and 44.7 % for conventional native MRI, native plus DWI, native with contrast-enhanced MRI (CE-MRI), for MPMRI, and for PET/CT, respectively. The overall detection rate proved by histology was 47.4 %. PET/CT provided the highest sensitivity (Sv: 94.4 %) but a lower specificity (Sp: 65.0 %), using MPMRI (Sv: 88.2 %) the specificity increased to 71.4 %. DWIincreased specificity of the native sequences (Sp: 76.2 %). Conventional native sequences plus DWI as well as 3T-MPMRI and PET/CT were same accurate (Acc: 79.0 %) and had similar likelihood ratio (LR: 3.42, 3.03 and 2.62) in detecting unknown PT sites.

Conclusions

The accuracy of FDG-PET/CT and MPMRI in case of CUP in finding the primary cancer in the neck regions is identical. While using PET/CT whole body information can be obtained in one examination. MPMRI shows the local soft tissue status more accurately. In cases of CUP PET/CT should be the first method of choice if it is available. MPMRI can clarify the exact primary tumor stage, and it can be advantageous in clarifying the prognostic factors, which is necessary in case of advanced tumor stage and when surgery is under consideration. In case low N stage is likely after the clinical examination and wait and see policy can be considered, MPMRI is recommended, and in this case the significance the of radiation free MPMRI is increasing.

Electronic supplementary material

The online version of this article (doi:10.1186/s40644-016-0097-x) contains supplementary material, which is available to authorized users.

Role of fluorine-18 fluorodeoxyglucose PET/CT in head and neck oncology: the point of view of the radiation oncologist

Squamous cell carcinoma is the most common malignant tumour of the head and neck. The initial TNM staging, the evaluation of the tumour response during treatment, and the long-term surveillance are crucial moments in the approach to head and neck squamous cell carcinoma (HNSCC). Thus, at each of these moments, the choice of the best diagnostic tool providing the more precise and larger information is crucial. Positron emission tomography with fluorine-18 fludeoxyglucose integrated with CT (¹⁸F-FDG-PET/CT) rapidly gained clinical acceptance, and it has become an important imaging tool in routine clinical oncology. However, controversial data are currently available, for example, on the role of ¹⁸F-FDG-PET/CT imaging during radiotherapy planning, the prognostic value or its real clinical impact on treatment decisions. In this article, the role of ¹⁸F-FDG-PET/CT imaging in HNSCC during pre-treatment staging, radiotherapy planning, treatment response assessment, prognosis and follow-up is reviewed focusing on current evidence and controversial issues. A proposal on how to integrate ¹⁸F-FDG-PET/CT in daily clinical practice is also described.

Contrast-enhanced [18F] fluorodeoxyglucose-positron emission tomography-computed tomography as an initial imaging modality in patients presenting with metastatic malignancy of undefined primary origin

Background:

To evaluate the advantages of contrast enhanced F-18-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-contrast enhanced CT [CECT]) when used as an initial imaging modality in patients presenting with metastatic malignancy of undefined primary origin (MUO).

Materials and Methods:

A total of 243 patients with fine needle aspiration cytology/biopsy proven MUO were included in this prospective study. Patients who were thoroughly evaluated for primary or primary tumor was detected by any other investigation were excluded from the analysis. Totally, 163 patients with pathological diagnosis of malignancy but no apparent sites of the primary tumor were finally selected for analysis. The site of probable primary malignancy suggested by PET-CECT was confirmed by biopsy/follow-up.

Results:

PET-CECT suggested probable site of primary in 128/163 (78.52%) patients. In 30/35 remaining patients, primary tumor was not detected even after extensive work-up. In 5 patients, where PET-CECT was negative, primary was found on further extensive investigations or follow-up. The sensitivity, specificity, positive predictive value and negative predictive value of the study were 95.76%, 66.67%, 88.28% and 85.71% respectively.

Conclusions:

F-18 FDG PET-CECT aptly serves the purpose of initial imaging modality owing to high sensitivity, negative and positive predictive value. PET-CECT not only surveys the whole body for the primary malignancy but also stages the disease accurately. Use of contrast improves the diagnostic utility of modality as well as help in staging of the primary tumor. Although benefits of using PET-CECT as initial diagnostic modality are obvious from this study, there is a need for a larger study comparing conventional methods for diagnosing primary in patients with MUO versus PET-CECT.

Basic principles and applications of (18)F-FDG-PET/CT in oral and maxillofacial imaging: A pictorial essay

A combination of positron emission tomography (PET) with ¹⁸F-labeled fluoro-2-deoxyglucose (¹⁸F-FDG) and computed tomography (¹⁸F-FDG-PET/CT) has increasingly become a widely used imaging modality for the diagnosis and management of head and neck cancer. On the basis of both recent literature and our professional experience, we present a set of principles with pictorial illustrations and clinical applications of FDG-PET/CT in the evaluation and management planning of squamous cell carcinoma of the oral cavity and oropharynx. We feel that this paper will be of interest and will aid the learning of oral and maxillofacial radiology trainees and practitioners.

[Importance of nuclear medicine diagnostics in CUP syndrome]

CLINICAL/METHODICAL ISSUE

The diagnostic work-up in patients with carcinoma of unknown primary (CUP) syndrome is extensive, highly time-consuming and cost-intensive and ultimately often fails to detect a primary site.

STANDARD RADIOLOGICAL METHODS

In this context chest X-ray and computed tomography (CT) have been used as standard imaging modalities in CUP syndrome.

METHODOLOGICAL INNOVATIONS

Since the introduction of positron emission tomography (PET) evaluation of tumor vitality has become possible. Furthermore, PET-CT hybrid scanners allow the combination of functional and morphological imaging.

PERFORMANCE

Several meta-analyses have reported an additional overall detection rate between 24.5 % and 44 % by either PET or PET-CT. Metastatic localization (cervical versus extracervical) did not influence the performance. The sensitivity was usually high (> 80 %) but specificity was moderate ranging from 68 % to 88 % at best. If mentioned, the results obtained by fluorodeoxyglucose (FDG)-PET significantly changed the clinical management in approximately one third of the patients studied. In a direct comparison with PET alone, PET-CT did not depict significantly more primary tumors but was able to reduce false positive findings.

ACHIEVEMENTS

To determine the real additional value of PET-CT in the diagnosis of CUP syndrome large prospective studies with more uniform inclusion criteria are needed. Despite the capabilities of FDG-PET-CT there is as yet no evidence that a potentially improved diagnostic algorithm is translated into a better patient outcome.

PRACTICAL RECOMMENDATIONS

Nevertheless, FDG-PET-CT should be performed in all CUP patients where conventional imaging failed to detect a primary site or the results are equivocal. In CUP patients with cervical lymph node metastases PET-CT should be carried out prior to panendoscopy to reduce the number of false negative biopsies.

Management of lymph node metastases from an unknown primary site to the head and neck (Review)

Cancer of unknown primary site (CUP) is an intriguing clinical phenomenon found in ~3-9% of all head and neck cancers. It has not yet been determined whether CUP forms a distinct biological entity with specific genetic and phenotypic characteristics, or whether it is the clinical presentation of metastasis in patients with an undetected primary tumor and no visible clinical signs. The treatment of patients with cervical lymph node metastases from CUP remains controversial, due to the lack of randomized clinical trials comparing different treatment options. Consequently, treatment is currently based on non-randomized data and institutional policy. In the present review, the range and limitations of diagnostic procedures are summarized and an optimal diagnostic work-up is recommended. The initial preferred diagnostic procedures include fine-needle aspiration biopsy (FNAB) and imaging. Although neck dissection followed by postoperative radiotherapy is the the most generally accepted approach, other curative options may be used in certain patients, such as neck dissection alone, nodal excision followed by postoperative radiotherapy, or radiotherapy alone. There remains controversy regarding target radiation volumes, ranging from ipsilateral neck irradiation to prophylactic irradiation of all the potential mucosal sites and both sides of the neck. When no primary lesion is identified with imaging and endoscopy in patients without history of smoking and alcohol abuse, molecular profiling of an FNAB sample for human papillomavirus and/or Epstein-Barr virus is required.

The added value of18F-fluorodeoxyglucose positron emission tomography computed tomography in patients with neck lymph node metastases from an unknown primary malignancy

Background:

The search for a primary malignancy in patients with a metastatic cervical lymph node is challenging yet ultimately of utmost clinical importance. This study evaluated the efficacy of positron emission tomography computed tomography in detecting the occult primary, within the context of a tertiary referral centre head and neck cancer multidisciplinary team tumour board meeting.

Methods:

Thirty-two patients (23 men and 9 women; mean and median age, 61 years) with a metastatic cervical lymph node of unknown primary origin, after clinical examination and magnetic resonance imaging, underwent positron emission tomography computed tomography.

Results:

The primary tumour detection rate was 50 per cent (16/32). Positron emission tomography computed tomography had a sensitivity of 94 per cent (16/17) and a specificity of 67 per cent (10/15). Combining these results with those of 10 earlier studies of similar patients gave an overall detection rate of 37 per cent.

Conclusion:

Positron emission tomography computed tomography has become an important imaging modality. To date, it has the highest primary tumour detection rate, for head and neck cancer patients presenting with cervical lymph node metastases from an unknown primary.

Initial staging of squamous cell carcinoma of the oral cavity, larynx and pharynx (excluding nasopharynx). Part I: Locoregional extension assessment: 2012 SFORL guidelines

OBJECTIVES

To set out good practice guidelines for locoregional extension assessment of squamous cell carcinoma of the head and neck (excluding nasopharynx, nasal cavities and sinuses).

MATERIALS AND METHODS

A critical multidisciplinary review of the literature on locoregional extension assessment of squamous cell carcinoma of the head and neck was conducted, applying levels of evidence in line with the French health authority's (HAS) literature analysis guide of January 2000.

CONCLUSION

Based on the levels of evidence of the selected articles and on work-group consensus, graded guidelines are set out for clinical, endoscopic and imaging locoregional extension assessment of head and neck cancer.

[Usefulness of (18)F-fluorodeoxyglucose-positron emission tomography-computerized tomography in the identification of the primary tumor in patients with cancer of unknown origin]

BACKGROUND AND OBJECTIVE

We determined the utility of the (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET)-computerized tomography (CT) in the localization of the primary tumor in patients with tumor of unknown origin (TUO).

PATIENTS AND METHOD

(18)F-FDG PET-CT scans, performed between November 2006 and November 2010, in search for the primary tumor in patients with TUO, were retrospectively evaluated. Patients underwent a standard PET-CT, 50-60minutes after intravenous injection of 296-370MBq (18)F-FDG. PET-CT studies were assessed as pathological, with/without identification of the primary tumour and no pathological. Final diagnosis was established by histological confirmation and/or clinical/radiologic follow-up longer than 6 months.

RESULTS

We studied 74 patients (59 males, 15 females), with ages ranging from 41-89 years. In 38 (51%) patients the PET-CT assessed the correct origin of the primary tumour. In 8 cases, a histological confirmation in the primary lesion was obtained. In 4 patients the PET-CT showed a false positive result.

CONCLUSION

PET-CT scanning identified 51% of the primary sites in our sample of patients.

[¹⁸F]fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography imaging in oncology: initial staging and evaluation of cancer therapy

Positron emission tomography (PET) with [¹⁸F]fluoro-2-deoxy-D-glucose (FDG) has proven to be a valuable diagnostic modality in various diseases. Its accuracy has been improved with the hybrid PET/computed tomography (CT) technique because of precise anatomic location of areas of abnormal FDG accumulation. This integrated PET/CT modality has been widely adopted, particularly in oncology. This paper reviews the role of FDG-PET/CT imaging in breast cancer, non-small-cell lung cancer, colorectal cancer, head and neck cancer as well as lymphoma on the basis of recent key articles. Special attention is paid to preoperative diagnostic workup, evaluation of treatment response and survival prognosis. Experience from specialized centers indicates that there is strong evidence for the clinical effectiveness of FDG-PET/CT in staging, restaging and the prediction of response to therapy in the above-mentioned malignancies. It is concluded that this imaging modality contributes considerably to improved patient management and paves the way to personalize cancer treatment in a cost-effective way.

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.

18F-fluorodeoxyglucose positron emission tomography/computed tomography in the assessment of occult primary head and neck cancers--an audit and review of published studies

AIMS

To assess the value of 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in patients with squamous cell and undifferentiated cancer neck nodes and no primary site on conventional assessment.

MATERIALS AND METHODS

Seventy-eight patients with neck nodal metastases from an unknown primary cancer were studied. PET/CT was carried out in all patients, 1h after FDG injection.

RESULTS

Uptake suspicious of an occult primary cancer was found in 46/78 (59.0%) patients. Subsequent investigations confirmed a primary site in the base of the tongue in 14, pharyngeal palatine tonsil in 14, post cricoid in one, lung in one. PET/CT diagnosed primary cancers in 30/78 patients (38.5%); sensitivity, specificity, positive predictive value, negative predictive value: 30/30 (100.0%), 32/48 (66.7%), 30/46 (65.2%), 32/32 (100.0%), respectively. PET/CT detected additional disease in four patients: contralateral nodal disease in two, mediastinal nodal disease in one and liver metastases in one.

CONCLUSIONS

FDG PET/CT is of value in the assessment of patients with occult head and neck primary cancers. However, false-positive results remain a limitation of the investigation.

Contemporary management of lymph node metastases from an unknown primary to the neck: I. A review of diagnostic approaches

In an era of advanced diagnostics, metastasis to cervical lymph nodes from an occult primary tumor is a rare clinical entity and accounts for approximately 3% of head and neck malignancies. Histologically, two thirds of cases are squamous cell carcinomas (SCCs), with other tissue types less common in the neck. With modern imaging and tissue examinations, a primary tumor initially undetected on physical examination is revealed in >50% of patients and the site of the index primary can be predicted with a high level of probability. In the present review, the range and limitations of diagnostic procedures are summarized and the optimal diagnostic workup is proposed. Initial preferred diagnostic procedures are a fine-needle aspiration biopsy (FNAB) and imaging. This allows directed surgical biopsy (such as tonsillectomy), based on the preliminary findings, and prevents misinterpretation of postsurgical images. When no primary lesion is suggested after imaging and panendoscopy, and for patients without a history of smoking and alcohol abuse, molecular profiling of an FNAB sample for human papillomavirus (HPV) and/or Epstein-Barr virus (EBV) is important.

PET/CT in Neuroendocrine Tumors: Evaluation of Receptor Status and Metabolism

In-111 Octreoscan is considered the gold standard for imaging of neuroendocrine tumors (NET). However, in the absence of morphologic imaging correlation, the exact localisation of the tumor is often difficult. Also the sensitivity of PET imaging is more than Gamma camera (SPECT) imaging. Ga-68 labelled somatostatin analogs (SMS-R) are interesting radiopharmaceuticals for PET receptor imaging of NET. Some other radiopharmaceuticals e.g. F-18 DOPA can also be used to assess metabolism and functional status of NET. The importance of these radiopharmaceuticals, especially SMS-R increases in the absence of any specific biochemical marker or clinical parameter for follow-up of patients after therapy (eg peptide receptor radionuclide therapy, surgery, chemoembolisation, etc). New criteria based on molecular, metabolic and morphologic imaging needs to be developed for correct assessment of response to therapy for these slow-growing, solid tumors.

Detection of unknown primary neuroendocrine tumours (CUP-NET) using (68)Ga-DOTA-NOC receptor PET/CT

PURPOSE

This bi-centric study aimed to determine the role of receptor PET/CT using (68)Ga-DOTA-NOC in the detection of undiagnosed primary sites of neuroendocrine tumours (NETs) and to understand the molecular behaviour of the primarily undiagnosed tumours.

METHODS

Overall 59 patients (33 men and 26 women, age: 65 + or - 9 years) with documented NET and unknown primary were enrolled. PET/CT was performed after injection of approximately 100 MBq (46-260 MBq) of (68)Ga-DOTA-NOC. The maximum standardised uptake values (SUV(max)) were calculated and compared with SUV(max) in known pancreatic NET (pNET) and ileum/jejunum/duodenum (SI-NET). The results of PET/CT were also correlated with CT alone.

RESULTS

In 35 of 59 patients (59%), (68)Ga-DOTA-NOC PET/CT localised the site of the primary: ileum/jejunum (14), pancreas (16), rectum/colon (2), lungs (2) and paraganglioma (1). CT alone (on retrospective analyses) confirmed the findings in 12 of 59 patients (20%). The mean SUV(max) of identified previously unknown pNET and SI-NET were 18.6 + or - 9.8 (range: 7.8-34.8) and 9.1 + or - 6.0 (range: 4.2-27.8), respectively. SUV(max) in patients with previously known pNET and SI-NET were 26.1 + or - 14.5 (range: 8.7-42.4) and 11.3 + or - 3.7 (range: 5.6-17.9). The SUV(max) of the unknown pNET and SI-NET were significantly lower (p < 0.05) as compared to the ones with known primary tumour sites; 19% of the patients had high-grade and 81% low-grade NET. Based on (68)Ga-DOTA-NOC receptor PET/CT, 6 of 59 patients were operated and the primary was removed (4 pancreatic, 1 ileal and 1 rectal tumour) resulting in a management change in approximately 10% of the patients. In the remaining 29 patients, because of the far advanced stage of the disease (due to distant metastases), the primary tumours were not operated. Additional histopathological sampling was available from one patient with bronchial carcinoid (through bronchoscopy).

CONCLUSION

Our data indicate that (68)Ga-DOTA-NOC PET/CT is highly superior to (111)In-OctreoScan (39% detection rate for CUP according to the literature) and can play a major role in the management of patients with CUP-NET.

FDG PET/CT in carcinoma of unknown primary

Carcinoma of unknown primary (CUP) is a heterogeneous group of metastatic malignancies in which a primary tumor could not be detected despite thorough diagnostic evaluation. Because of its high sensitivity for the detection of lesions, combined ¹⁸F-fluoro-2-deoxyglucose positron emission tomography (FDG PET)/computed tomography (CT) may be an excellent alternative to CT alone and conventional magnetic resonance imaging in detecting the unknown primary tumor. This article will review the use, diagnostic performance, and utility of FDG PET/CT in CUP and will discuss challenges and future considerations in the diagnostic management of CUP.

Serial FDG-PET on patients with head and neck cancer: implications for radiation therapy

PURPOSE

To assess possible consequences for radiotherapy (RT) planning, e.g., reduction of treatment volume by a decreased tumour volume in Fluor-18-fluoro-deoxy-glucose-Positron emission tomography (FDG-PET) based on a close-meshed evaluation of FDG uptake in primary head and neck cancer (HNC) during RT.

MATERIALS AND METHOD

PET data were analysed using a source-to-background based algorithm. The following parameters were obtained: max. standardised uptake value (SUVmax), PET-based gross tumour volume (GTV-PET) and metabolic volume (MV).

RESULTS

While the median SUVmax decreased (initial: 15.2, 1st/2nd week: 10.2, 3rd/4th week: 6.5, 5th/6th week: 6.4), the median values of GTV-PET (9.3 cm(3), 12.4 cm(3), 14.0 cm(3), 17.9 cm(3)) and MV (92.2 cm(3), 61.7 cm(3), 60.0 cm(3), 71.3 cm(3)) seemed to increase during radiotherapy. The intra-individual development of SUVmax could be divided into two groups: group A having continuously decreasing values of SUVmax (n = 10 patients), and group B having a temporary increase of SUVmax (n = 13).

CONCLUSIONS

Data suggest that a reduction of treatment volume is not possible by an adaptive re-planning based on FDG-PET, e.g., at 50 Gy. This may be caused by a consecutive therapy associated inflammation. This limitation is probably related to the use of a source-to-background based algorithm.

Evaluation of the role of 18FDG-PET/CT in radiotherapy target definition in patients with head and neck cancer

BACKGROUND AND PURPOSE

As techniques for radiotherapy delivery have developed, increasingly accurate localisation of disease is demanded. Functional imaging, particularly PET and its fusion with anatomical modalities, such as PET/CT, promises to improve detection and characterisation of disease. This study evaluated the impact of (18)FDG-PET/CT on radiotherapy target volume definition in head and neck cancer (HNC).

MATERIALS AND METHODS

The PET/CT scans of patients with HNC were used in a radiotherapy planning (RTP) study. The gross tumour volume (GTV), clinical target volume (CTV) and planning target volume (PTV) were defined conventionally and compared to those defined using the PET/CT. Data were reported as the median value with 95% confidence intervals.

RESULTS

Eighteen patients were consented, 9 had known primary tumour site, 9 presented as unknown primary. In nine cases where the primary site was known, the combined primary and nodal GTV (GTVp+n) increased by a median of 6.1cm(3) (2.6, 12.2) or 78% (18, 313), p=0.008 with CTV increasing by a median of 10.1cm(3) (1.3, 30.6) or 4% (0, 13) p=0.012. In 9 cases of unknown primary the GTVp+n increased by a median 6.3 cm(3) (0.2, 15.7) or 61% (4, 210), p=0.012, with CTV increasing by a median 155.4 cm(3) (2.7, 281.7) or 95% (1, 137), p=0.008.

CONCLUSION

(18)FDG-PET revealed disease lying outside the conventional target volume, either extending a known area or highlighting a previously unknown area of disease, including the primary tumour in 5 cases. We recommend PET/CT in the RTP of all cases of unknown primary. In patients with a known primary, although the change in volume was statistically significant the clinical impact is less clear. (18)FDG-PET can also show areas within the conventional target volume that are hypermetabolic which may be possible biological target volumes for dose escalation studies in the future.

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.

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.

Integrated PET/CT system for staging and surveillance of skull base tumors

BACKGROUND

The utility of preoperative and postoperative whole body integrated positron emission tomography-computed tomography (PET-CT) scanning for staging and follow-up in patients with skull base tumors is undetermined.

METHODS

We prospectively evaluated PET-CT findings in 47 patients using 57 scans. Most (35/47, 75%) had anterior skull base tumors and the majority (74%) had advanced-stage (III-IV) disease.

RESULTS

The scans showed high sensitivity for detection of various types of malignant tumors and provided 39 items of additional information, changing the clinical staging and management of 11 patients (23%). Recurrence of primary tumors was detected in 8 patients, positive regional (neck) metastases in 3, and distant metastases in 3. The positive uptake was due to osteoradionecrosis in 2 other patients. The sensitivity of PET-CT was 0.77 and the specificity was 0.81 (0.83 positive predictive value and 0.76 negative predictive value).

CONCLUSIONS

PET-CT provides accurate data on anatomy, tumor staging, and early disease recurrence in the skull base.

PET/CT in oncology: for which tumours is it the reference standard?

Positron emission tomography (PET)/computed tomography (CT) has a growing role in the imaging of many cancers. As our experience has grown over the past number of years so has our understanding for which cancers it is particularly useful. The value of PET/CT at each stage of the cancer journey is different for each cancer. This review attempts to tease out the role of PET/CT in the common cancers with particular emphasis on where it is the imaging investigation of choice.

Impact of PET-FDG in the diagnosis and therapeutic care of patients presenting with metastases of unknown primary

We carried out a study to evaluate the contribution of positron emission tomography with (18)F-fluorodeoxyglucose (PET-FDG) in the diagnosis and therapeutic care of patients presenting with metastases of unknown primary. PET-FDG was prospectively performed in 51 patients. The PET-FDG data were confirmed histologically or by a follow-up on average at 13 months. PET-FDG identified the primary in 24 percent of cases, and detected the presence of additional metastases in 41 percent of cases. PET-FDG led to a therapeutic modification for 12 patients (24 percent). Furthermore, the therapeutic impact seems more marked in localized forms than in the multifocal. This broad exploratory study confirms the important role of PET-FDG in the diagnosis and therapeutic management of patients with metastases of unknown primary.

Prognostic and diagnostic accuracy of [18F]FDG-PET/CT in 190 patients with carcinoma of unknown primary

PURPOSE

The aim of the study was to determine the accuracy of [(18)F]fluorodeoxyglucose (FDG) PET/CT in the search for the primary and the presence of a malignancy. The prognostic value of FDG-PET/CT information was tested.

METHODS

A total of 190 patients were retrospectively analysed: 82 with histologically proven metastases (HPM) and 108 with clinical suspicion of the presence of a malignancy (CSM). The sensitivity and specificity were determined. Overall survival was calculated to evaluate the prognostic value of the FDG-PET/CT findings.

RESULTS

In the search for the primary, the sensitivity and specificity were 62.0% and 81.9%, respectively. In the search for the presence of a malignancy, the sensitivity and specificity were 93.6% and 85.7%, respectively. Between the HPM and CSM groups, no significant difference in sensitivity and specificity was found either in the search for the primary or in the search for the presence of a malignancy. No significant difference in the sensitivity and specificity was found between 78 patients who were investigated by contrast-enhanced FDG-PET/CT and the remaining patients. A significantly shorter overall survival was found among patients with positive FDG-PET/CT findings compared with patients with negative findings (p = 0.00001); no significant difference in survival was found between the HPM and the CSM group (p = 0.770).

CONCLUSION

FDG-PET/CT imaging is very helpful in the search for the presence of a malignancy in patients with carcinoma of unknown primary syndrome. FDG-PET/CT is less accurate in identifying exactly the site of a primary. Discovery of a hypermetabolic lesion was associated with the worst survival rate.

In search of an unknown primary tumour presenting with cervical metastases: Performance of hybrid FDG-PET–CT

OBJECTIVES

In patients with cervical lymph node metastases from unknown primary tumour (UPT), the primary tumour is frequently localized in the head and neck area. Because the detection of the primary tumour is of importance to optimize the patient's management and allows a targeted therapy, the performances of hybrid positron emission tomography-computed tomography (PET-CT) using fluorodeoxyglucose (FDG) were evaluated in a retrospective study.

METHODS

Thirty-eight consecutive patients with cervical lymph node metastases, and in whom the primary was not detected by the comprehensive diagnostic work-up including endoscopy and conventional imaging methods, were referred for a PET-CT scan.

RESULTS

PET-CT was positive with an increased FDG focal uptake suggesting the potential primary site in 68% of patients (26/38), which guided the biopsies during a second rigid panendoscopy in 17 of these 26 patients: 13 primary tumours were then histologically proven. PET-CT showed distant lesions in three patients. It had treatment-related implications in 23/38 patients (60%), consisting of modification of radiation planning, surgery or abstention from surgery.

CONCLUSION

Hybrid FDG-PET-CT is helpful for the detection of a potential head and neck primary tumour. Furthermore, hybrid FDG-PET-CT has the ability to diagnose occult or distant second tumour and metastatic disease and modify patient management.

PET/CT: form and function

Functional imaging with positron emission tomography (PET) is playing an increasingly important role in the diagnosis and staging of malignant disease, image-guided therapy planning, and treatment monitoring. PET with the labeled glucose analogue fluorine 18 fluorodeoxyglucose (FDG) is a relatively recent addition to the medical technology for imaging of cancer, and FDG PET complements the more conventional anatomic imaging modalities of computed tomography (CT) and magnetic resonance imaging. CT is complementary in the sense that it provides accurate localization of organs and lesions, while PET maps both normal and abnormal tissue function. When combined, the two modalities can help both identify and localize functional abnormalities. Attempts to align CT and PET data sets with fusion software are generally successful in the brain; other areas of the body is more challenging, owing to the increased number of degrees of freedom between the two data sets. These challenges have recently been addressed by the introduction of the combined PET/CT scanner, a hardware-oriented approach to image fusion. With such a device, accurately registered anatomic and functional images can be acquired for each patient in a single scanning session. Currently, over 800 combined PET/CT scanners are installed in medical institutions worldwide, many of them for the diagnosis and staging of malignant disease and increasingly for monitoring of the response to therapy. This review will describe some of the most recent technologic developments in PET/CT instrumentation and the clinical indications for which combined PET/CT has been shown to be more useful than PET and CT performed separately.