Metastatic head and neck cancer: role and usefulness of FDG PET in locating occult primary tumors

Correlation between 18F-FDG PET/CT and diffusion-weighted MRI parameters in head and neck squamous cell carcinoma at baseline and after chemo-radiotherapy. A retrospective single institutional study

OBJECTIVES

The relationship between glucose metabolism and tumor cellularity before chemo-radiotherapy in patients with head and neck squamous cell carcinoma (SCC) has never been compared with that of patients evaluated after treatment. This retrospective study analyzed the correlation between glucose metabolism parameters expressed by standardized uptake value (SUV) derived from 18F-fluorodeoxyglucose (18F-FDG) PET/CT and cellularity tumor parameters expressed by apparent diffusion coefficients (ADC) derived from diffusion-weighted (DW) MRI in untreated and treated patients with head and neck SCC.

METHODS

In 19 patients with no previous exposure to any treatment and 17 different chemo-radiotreated patients with head and neck SCC, we correlated the semi-quantitative uptake values (SUVmax, SUVpeak, and SUVmean) with the ADC functional parameters (ADCmin, ADCmean) including the standard deviation of ADC values (ADCsd).

RESULTS

No significant correlation was found between glucose metabolism parameters and ADCmin or ADCmean in untreated and treated patient groups. However, in untreated patients, significant inverse correlations were found between ADCsd and SUVmax (P = 0.039, r = -0.476), SUVpeak (P = 0.003, r = -0.652) and SUVmean (P = 0.039, r = -0.477). Analyses after chemo-radiotherapy in 17 patients showed no significant correlation between glucose metabolism parameters and DW MRI values, excluding a persistent significant (but lower intensity) inverse correlation between SUVpeak and ADCsd (P = 0.033, r = -0.519).

CONCLUSIONS

The demonstrated relationships suggest complex interactions especially between metabolic activity and heterogeneity of tumoral tissue, which might play a complementary role in the assessment of head and neck SCC.

TRIAL DATE OF REGISTRATION AND REGISTRATION NUMBER

Our retrospective study was registered on April 9th, 2020 by the Ethics Committee of the Coordinating Center "Area Vasta Nord Ovest" (CEAVNO) with Registration Number CEAVNO09042020.

Diagnostic approaches to carcinoma of unknown primary of the head and neck

Squamous cell carcinoma in cervical lymph nodes arising from an undetected primary tumour, termed carcinoma of unknown primary (SCCUP), is a well-recognized clinical presentation within head and neck oncology. SCCUP is a common presentation for patients with human papillomavirus-mediated oropharyngeal cancer (HPV + OPSCC), as patients with HPV + OPSCC often present with smaller primary tumours and early nodal metastasis. Meticulous work-up of the SCCUP patient is central to the management of these patients as identification of the primary site improves overall survival and allows for definitive oncologic resection or more focused radiation when indicated. This review summarizes the comprehensive diagnostic approach to the SCCUP patient, including history and physical examination, methods of biopsy of the cervical lymph node, imaging modalities and intraoperative methods to localize the unknown primary. Novel techniques such as transcervical ultrasound of the oropharynx, narrow band imaging and diagnostic transoral robotic surgery are also discussed.

Diffusion-weighted imaging as a part of PET/MR for small lesion detection in patients with primary abdominal and pelvic cancer, with or without TOF reconstruction technique

OBJECTIVES

To investigate the value of diffusion-weighted imaging (DWI) in detection of small lesions (≤ 10 mm) in patients with primary abdominal and pelvic cancer in hybrid PET/MR with or without time-of-flight (TOF) technique.

MATERIALS AND METHODS

Twenty patients (11 females and 9 males, mean age 67.23 ± 12.90 years) with histologically confirmed primary abdominal and pelvic cancer underwent hybrid PET/MR examination. A total of 64 small lesions were included in this study, which were divided into two groups (≤ 10 mm and 10-30 mm). Visual scores of small lesion detection ability were rated by five-point ordinal scale. The visual scores and detectability of small lesions on TOF PET image, noTOF PET image, and DWI sequences of hybrid PET/MR examination with or without TOF technique were analyzed. Logistic regression model was established for analysis in the value of DWI in hybrid PET/MR examination with or without TOF technique in detection of the small lesions between two groups.

RESULTS

The visual evaluation revealed the small lesion (≤ 10 mm) visual scores of DWI (mean ± SD: 4.23 ± 1.41), TOF PET image (mean ± SD: 4.14 ± 0.89), and noTOF PET image (mean ± SD: 2.68 ± 1.13);.and the visual scores of small lesions (10-30 mm) on DWI (mean ± SD: 4.98 ± 0.15), TOF PET image (mean ± SD: 4.57 ± 0.59), and noTOF PET image (mean ± SD: 3.98 ± 1.05). The visual scores of all small lesions on DWI were higher than that on TOF PET data and noTOF PET data in both two groups (**P < 0.01). The missed diagnosis rates of small FDG avid lesions (≤ 10 mm) of DWI and noTOF PET image were 9.1% and 9.1%, respectively. However, the TOF PET-based clinical diagnosis detected all small lesions (≤ 30 mm). DWI was of great importance in detection of small lesions (≤ 10 mm) in the absence of TOF technique in PET/MR examination (**P < 0.01). DWI's effect on detection of small lesions(10-30 mm) has shown no difference between PET/MR examinations with TOF and without TOF techniques (P > 0.05).

CONCLUSION

DWI has significant value in the detection of small lesions (≤ 10 mm) in hybrid PET/MR examination without TOF technique for patients with primary abdominal and pelvic cancer. However, it had less detection benefits in the small lesions (≤ 10 mm) in hybrid PET/MR examination with TOF PET image.

Preclinical PET imaging of HIP/PAP using 1'-18F-fluoroethyl-β-D-lactose

Purpose

This study aims at preclinical evaluation of a recently reported lactose analogue, 1'-¹⁸F-fluoroethyl-β-D-lactose (¹⁸F-FEL), in binding to hepatocarcinoma-intestine-pancreas and pancreatitis-associated protein (HIP/PAP) in vitro and in vivo.

Methods

In this study, a multifunctional module was employed for the automated synthesis of ¹⁸F-FEL. Additional radiochemical purity, biodistribution, in vitro and in vivo competition, metabolic stability and micro-PET studies were performed using T3M4 and SK-BR-3 xenografts. Expression of HIP/PAP in T3M4 and SK-BR-3 tumor sections and cell lines were tested with immunohistochemistry (IHC) and western blot analysis.

Results

The synthesis of ¹⁸F-FEL was completed in 30 min, with a radiochemical yield of 20 ± 5% and specific activity of 14.2 ± 7.1 GBq/μmol. ¹⁸F-FEL exhibited high HIP/PAP-binding affinity with a half maximal inhibitory concentration (IC50) of 22.0 ± 4.0 nM. ¹⁸F-FEL demonstrated high stability and specific tumor accumulation, which was reduced by approximately 80% in a PET competition assay by co-injection of β-D-lactose. High expression of HIP/PAP was detected in T3M4 tumors and cell line, but negative result was found for SK-BR-3 cell line.

Conclusion

¹⁸F-FEL has a high binding property to HIP/PAP, high stability and excellent pharmacokinetics in vivo and therefore warrants further evaluation in a proof-of-concept study in humans.

Demographics of Head and Neck Cancer Patients: A Single Institution Experience

Introduction Head and neck cancer (HNC) comprises a diverse group of oncological entities, originating from various tissue types and organ localizations, situated in the topographical regions of the head and neck (H&N). This single institution retrospective study was aimed at establishing the HNC patient demographics and categorizing the individual incidence of H&N malignancies, regarding their organ of origin and main histopathological type. Materials and methods All histologically verified cases of HNC from a single tertiary referral center were reviewed in a descriptive retrospective manner. Data sampling period was 47 months. Results Male to female ratio of the registered HNC cases was 3.24:1. The mean age of diagnosis was 63.84 ± 12.65 years, median 65 years. The most common HNC locations include the larynx 30.37% (n = 188), lips and oral cavity 29.08% (n = 180), pharynx 20.03% (n = 124) and salivary glands 10.94% (n = 68), with other locations such as the external nose, nasal cavity and sinuses and auricle and external ear canal harboring a minority of the cases. The main histopathological groups include squamous cell carcinoma 76.74% (n = 475) and adenocarcinoma 6.14% (n = 38), with other malignant entries such as other epithelial malignancies, primary tonsillar, mucosa-associated lymphoid tissue or parenchymal lymphomas, connective tissue neoplasias, neuroendocrine and vascular malignancies diagnosed in a minority of cases. Conclusion Considered to be relatively rare, HNC represents a diverse group of oncological entities with individual and specific demographic characteristics. The reported single institution results appear representative of the national incidence and characteristics of HNC.

Five-year outcomes of an oropharynx-directed treatment approach for unknown primary of the head and neck

PURPOSE

Squamous cell carcinoma of unknown primary (SCCHNUP) is commonly treated with comprehensive radiation to the laryngopharynx and bilateral necks. In 1998, we established a departmental policy to treat SCCHNUP with radiation directed to the oropharynx and bilateral neck.

METHODS

From 1998-2011, 60 patients were treated - N1: 18%, N2: 75% and N3: 7%. 82% underwent neck dissection. 55% received IMRT and 62% underwent concurrent chemoradiotherapy.

RESULTS

At median follow-up of 54months, 5 patients failed regionally and 4 emerged with a primary (tongue base, hypopharynx and thoracic esophagus). Five-year rates of regional control, primary emergence, distant metastasis, disease-free survival and overall survival were 90%, 10%, 20%, 72% and 79%, respectively. The 5year rate of primary emergence in a non-oropharynx site was 3%.

CONCLUSION

This is the first demonstration that an oropharynx-directed approach yields low rates of primary emergence in SCCHNUP with excellent oncologic outcomes.

Management delays in patients with squamous cell cancer of neck node(s) and unknown primary site: a retrospective cohort study

BACKGROUND

We aim to characterize the workup received by and identify any delays to diagnosis or treatment in patients referred to a tertiary cancer centre with the diagnosis of squamous cell carcinoma in neck node(s) and no identifiable primary (SCCNIP).

METHODS

Over 1 year, 68 patients were initially referred to the Head and Neck clinic with a label of "primary unknown". After extensive workup, 29 of the 68 patients were found to have pathologically confirmed SCCNIP. For these 29 patients, imaging tests, biopsies, examinations and times to treatment were reviewed and compared to 145 patients referred for known primaries.

RESULTS

In 21/29 (72%) patients, ultrasound was ordered prior to biopsy or referral. After referral, the first imaging test used was CT neck in 28 patients and PET/CT in 1 patient. Median time from referral to primary identification (n = 23) or workup completion (n = 6) were 16 (range: 0-48) and 36 (17-82) days respectively. Median time from referral to treatment was 55 (27-90; n = 26) days and was longer than those referred for known primaries (48 days; 20-162; p < 0.001). Across all patients, median time between first diagnostic imaging test and pathologic diagnosis were 20.5 and -8.0 days (p < 0.0001) in patients receiving ultrasound and CT, respectively.

CONCLUSIONS

In our cohort, delays to management were linked to community use of ultrasound and scheduling of both CT and PET/CT after thorough head and neck examination in patients with SCCNIP.

Role of Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography in the Evaluation of Head and Neck Carcinoma

Fluorodeoxyglucose (FDG)-positron emission tomography-computed tomography (PET-CT) has been playing a pivotal role in tumor imaging for the past 20 years. Head and neck (HN) cancers are a good example that can illustrate such unique role of FDG imaging contributing to the patient's management. In this review article, we will describe the normal physiological distribution of FDG within HN structures focusing on its limitations and pitfalls. In addition, we will be also describing its role in the initial staging and restaging of the disease, particularly with regard to therapy response assessment. Furthermore, its role in the evaluation of patients with malignant cervical adenopathy from an unknown primary will be described. In 2016, the Royal College of Radiologists in its third edition published evidence-based guidelines for PET-CT use in HN cancer emphasizing its rule in all these clinical scenarios that are being described in this review. Finally, we will be highlighting future directions in the field of molecular imaging of HN tumors with a special emphasis on the new PET tracers.

Advantages and disadvantages of F-18 fluorodeoxyglucose positron emission tomography/computed tomography in carcinoma of unknown primary

Carcinoma of unknown primary is a type of malignant disease where the primary carcinoma cannot be identified by conventional examination, which presents challenges in diagnosis and therapy. This study aims to evaluate the detailed clinical value and indications of using fluorine-18-2-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (F-18 FDG PET/CT) in a large sample. A total of 449 patients who were selected under strict standards were retrospectively included in this study. F-18 FDG PET/CT accurately detected the primary carcinoma in 115 of 449 patients whose primaries could not be detected by conventional examination (25.6%), with additional 27 false-positive patients. The most common primary site was the lung (34.8%). In addition, except for in metastatic melanoma (1/19, 5.3%) and axillary metastasis patients (2/49, 4.1%), F-18 FDG PET/CT had a comparative performance in detecting primary carcinoma in other pathological types and anatomical locations. The scan is able to guide treatment strategy modifications to some extent (130/449, 29.0%). We strongly recommend the use of F-18 FDG PET/CT in the early phase of examination. It is also recommended as a supplementary radiological method, and certain patients may benefit from its application in cases where regular examination is inconclusive. However, in metastatic melanoma or axillary metastasis patients where the primary site cannot be identified by routine examination, regular application of F-18 FDG PET/CT for the sole purpose of detecting the primary carcinoma should not be encouraged.

Infection Imaging With (18)F-FDS and First-in-Human Evaluation

PURPOSE

The noninvasive imaging of bacterial infections is critical in order to reduce mortality and morbidity caused by these diseases. The recently reported (18)F-FDS ((18)F-2-fluorodeoxy sorbitol) as a PET (positron emission tomography) tracer can be used to image Enterobacteriaceae-specific infections and provides a potential alternative to this problem compared with other probes for imaging infections. In this study, automatic synthesis, validation of (18)F-FDS and a first-in-human study were performed and discussed.

METHODS

A multifunctional synthesis module was employed for the radiosynthesis of (18)F-FDG ((18)F-2-fluorodeoxy glucose) and (18)F-FDS starting from (18)F ion using two-pot three-step fully automated reactions. The behavior of (18)F-FDS as an in vivo imaging probe for infections was evaluated in an Escherichia coli mouse infection model. The first detailed pharmacokinetic and biodistribution parameters were obtained from healthy human volunteers.

RESULTS

The uptake of (18)F-FDS in an E. coli mouse-myositis infection model was easily differentiated from other organs and normal muscle. Intensive lesion uptake declined after antibiotic treatment. In the pilot human study, no adverse effects due to (18)F-FDS were observed up to 24 h post-injection. The radiotracer was rapidly cleared from the circulation and excreted mainly through the urinary system.

CONCLUSION

We conclude that (18)F-FDS PET holds great potential for appropriate and effective for the imaging of bacterial infections in vivo. These preliminary results indicate that further clinical studies are warranted.

Locoregional tumour evaluation of squamous cell carcinoma in the head and neck area: a comparison between MRI, PET/CT and integrated PET/MRI

PURPOSE

To evaluate the accuracy of integrated (18)F-FDG PET/MR imaging for locoregional tumour evaluation compared to (18)F-FDG PET/CT and MR imaging in initial tumour and recurrence diagnosis in histopathologically confirmed head and neck squamous cell carcinoma (HNSCC).

METHODS

(18)F-FDG PET/CT and integrated (18)F-FDG PET/MR imaging were performed for initial tumour staging or recurrence diagnosis in 25 patients with HNSCC. MR, fused (18)F-FDG PET/CT and fused (18)F-FDG PET/MR images were analysed by two independent readers in separate sessions in random order. In initial tumour staging, T and N staging was performed while individual lesions were analysed in patients with suspected cancer recurrence. In T and N staging, histopathological results after tumour resection served as the reference standard while histopathological sampling as well as cross-sectional and clinical follow-up were accepted in cancer recurrence diagnosis. The diagnostic accuracy of each modality was calculated separately for T and N staging as well as for tumour recurrence, and compared using McNemar's test. Values of p <0.017 were considered statistically significant after Bonferroni correction.

RESULTS

In 12 patients undergoing (18)F-FDG PET/CT and (18)F-FDG PET/MR for initial tumour staging, T staging was accurate in 50 % with MRI, in 59 % with PET/CT and in 75 % with PET/MR while N staging was accurate in 75 % with MRI, in 77 % with PET/CT and in 71 % with PET/MR in relation to the reference standard. No significant differences were observed in T and N staging among the three modalities (p > 0.017). In 13 patients undergoing hybrid imaging for cancer recurrence diagnosis, diagnostic accuracy was 57 % with MRI and in 72 % with (18)F-FDG PET/CT and (18)F-FDG PET/MR, respectively. Again, no significant differences were found among the three modalities (p > 0.017).

CONCLUSION

In this initial study, no significant differences were found among (18)F-FDG PET/MR, (18)F-FDG PET/CT and MRI in local tumour staging and cancer recurrence diagnosis.

Diagnostic value of diffusion-weighted imaging in simultaneous 18F-FDG PET/MR imaging for whole-body staging of women with pelvic malignancies

The aim of this study was to assess the diagnostic benefit of diffusion-weighted imaging (DWI) in an (18)F-FDG PET/MR imaging protocol for whole-body staging of women with primary or recurrent malignancies of the pelvis.

METHODS

Forty-eight patients with a primary pelvic malignancy or suspected recurrence of a pelvic malignancy were included in our study. All patients underwent a whole-body (18)F-FDG PET/MR imaging examination that included DWI. Two radiologists separately evaluated the PET/MR imaging datasets without DWI followed by a second interpretation with DWI. First, both readers identified all primary tumors, as well as lymph node and distant metastases. In a second session, PET and DWI data were assessed qualitatively. Image interpretation comprised lesion conspicuity defined as visual lesion-to-background contrast (4-point ordinal scale) and diagnostic confidence (3-point ordinal scale) for all tumors. The results from histopathologic examination and cross-sectional imaging follow-up (≥6 mo) were used as the reference standard. Statistical analysis was performed to assess the significance of differences between obtained values.

RESULTS

Among the 122 suspected lesions seen, 98 (80.3%) were considered malignant. PET/MR imaging without DWI had a sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of 92.9%, 87.5%, 96.8%, 75.0%, and 91.8%, respectively, for the detection of malignant lesions. PET/MR imaging with DWI had slightly higher values (94.9%, 83.3%, 95.9%, 80.0%, and 92.6%, respectively), but the difference was not significant (P > 0.05). In the qualitative assessment of lesion-to-background contrast, PET had significantly (P < 0.05) higher values (3.79 ± 0.58) than DWI (3.63 ± 0.77). Furthermore, significantly (P < 0.05) higher scores were found for diagnostic confidence using PET (2.68 ± 0.64) for the determination of malignant lesions, when compared with DWI (2.53 ± 0.69).

CONCLUSION

DWI in PET/MR imaging has no diagnostic benefit for whole-body staging of women with pelvic malignancies. The omission of DWI for staging or restaging gynecologic cancer may significantly reduce examination times, thus increasing patient comfort without a relevant decrease in diagnostic competence.

Investigation strategy in the management of metastatic adenocarcinoma of unknown primary presenting as cervical lymphadenopathy

CONCLUSION

Computed tomography (CT) of the neck, chest, abdomen and pelvis is the most appropriate initial investigation following a fine needle aspiration cytology (FNAC) diagnosis of metastatic adenocarcinoma in cervical lymph nodes with unknown primary. PET-CT should be considered as the next step if the initial CT fails to identify the primary site, but its true value is yet to be determined.

OBJECTIVE

To review investigation strategies for metastatic adenocarcinoma of unknown primary presenting as cervical lymphadenopathy, and to develop a management algorithm.

METHODS

This was a retrospective case note study from two regional head and neck cancer centres in the UK. Adult patients with FNAC diagnosis of metastatic adenocarcinoma in cervical lymph nodes between 1998 and 2008, with a minimum 5-year follow-up, were included. Patients with a clinically obvious primary tumour or a previous history of adenocarcinoma were excluded.

RESULTS

This study examined 41 cases. CT of the neck, chest, abdomen and pelvis was the most useful initial investigation. It identified the primary tumour site in 16/28 cases (57%), detected the primary tumour and led to revision of the FNAC diagnosis in 1 case (2.4%), and was necessary for the final diagnosis of true unknown primary in 12 cases (29.3%). Targeted imaging was not helpful.

The Outline of Prognosis and New Advances in Diagnosis of Oral Squamous Cell Carcinoma (OSCC): Review of the Literature

Objective. Oral squamous cell carcinoma (OSCC) has a remarkable incidence over the world and a fairly strenuous prognosis, encouraging further research on the prognostic factors and new techniques for diagnosis that might modify disease outcome. Data Sources. A web-based search for all types of articles published was initiated using Medline/Pub Med, with the key words such as oral cancer, prognostic factors of oral cancer, diagnostic method of oral cancer, and imaging techniques for diagnosis of oral cancer. The search was restricted to articles published in English, with no publication date restriction (last update April, 2013). Review Methods. In this paper, I approach the factors of prognosis of OSCC and the new advances in diagnostic technologies as well. I also reviewed available studies of the tissue fluorescence spectroscopy and other noninvasive diagnostic aids for OSCC. Results. The outcome is greatly influenced by the stage of the disease (especially TNM). Prognosis also depends or varies with tumour primary site, nodal involvement, tumour thickness, and the status of the surgical margins. Conclusion. Tumour diameter is not the most accurate when compared to tumour thickness or depth of invasion, which can be related directly to prognosis. There is a wide agreement on using ultrasound guided fine needle aspiration biopsies in the evaluation of lymph node metastasis.

Cancer metabolism, stemness and tumor recurrence: MCT1 and MCT4 are functional biomarkers of metabolic symbiosis in head and neck cancer

Here, we interrogated head and neck cancer (HNSCC) specimens (n = 12) to examine if different metabolic compartments (oxidative vs. glycolytic) co-exist in human tumors. A large panel of well-established biomarkers was employed to determine the metabolic state of proliferative cancer cells. Interestingly, cell proliferation in cancer cells, as marked by Ki-67 immunostaining, was strictly correlated with oxidative mitochondrial metabolism (OXPHOS) and the uptake of mitochondrial fuels, as detected via MCT1 expression (p < 0.001). More specifically, three metabolic tumor compartments were delineated: (1) proliferative and mitochondrial-rich cancer cells (Ki-67+/TOMM20+/COX+/MCT1+); (2) non-proliferative and mitochondrial-poor cancer cells (Ki-67−/TOMM20−/COX−/MCT1−); and (3) non-proliferative and mitochondrial-poor stromal cells (Ki-67−/TOMM20−/COX−/MCT1−). In addition, high oxidative stress (MCT4+) was very specific for cancer tissues. Thus, we next evaluated the prognostic value of MCT4 in a second independent patient cohort (n = 40). Most importantly, oxidative stress (MCT4+) in non-proliferating epithelial cancer cells predicted poor clinical outcome (tumor recurrence; p < 0.0001; log-rank test), and was functionally associated with FDG-PET avidity (p < 0.04). Similarly, oxidative stress (MCT4+) in tumor stromal cells was specifically associated with higher tumor stage (p < 0.03), and was a highly specific marker for cancer-associated fibroblasts (p < 0.001). We propose that oxidative stress is a key hallmark of tumor tissues that drives high-energy metabolism in adjacent proliferating mitochondrial-rich cancer cells, via the paracrine transfer of mitochondrial fuels (such as L-lactate and ketone bodies). New antioxidants and MCT4 inhibitors should be developed to metabolically target “three-compartment tumor metabolism” in head and neck cancers. It is remarkable that two “non-proliferating” populations of cells (Ki-67−/MCT4+) within the tumor can actually determine clinical outcome, likely by providing high-energy mitochondrial “fuels” for proliferative cancer cells to burn. Finally, we also show that in normal mucosal tissue, the basal epithelial “stem cell” layer is hyper-proliferative (Ki-67+), mitochondrial-rich (TOMM20+/COX+) and is metabolically programmed to use mitochondrial fuels (MCT1+), such as ketone bodies and L-lactate. Thus, oxidative mitochondrial metabolism (OXPHOS) is a common feature of both (1) normal stem cells and (2) proliferating cancer cells. As such, we should consider metabolically treating cancer patients with mitochondrial inhibitors (such as Metformin), and/or with a combination of MCT1 and MCT4 inhibitors, to target “metabolic symbiosis.”

Clinical value of whole-body F-18 fluorodeoxyglucose positron emission tomography/computed tomography in patients with carcinoma of unknown primary

INTRODUCTION

The purpose of the study is to investigate the clinical value of F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in detecting the primary sites in patients with carcinoma of unknown primary (CUP).

METHODS

The reports of FDG PET/CT scans of 164 patients with CUP syndrome in consecutive 2589 patients referred to our department from January 2006 to June 2010 were retrospectively reviewed. The final results were obtained from the pathologic reports, other imaging modalities diagnoses and clinical follow-up data.

RESULTS

There were 142 cases in the results analysis, as 19 patients were lost to follow-up and three patients were excluded. FDG PET/CT successfully detected primary tumours in 67 (47.2%) out of 142 patients. Among this group, 53 were pathologically proved and 17 patients were confirmed by clinical follow-up. The primary sites of 38 (56.7%) were in lung, eight (11.9%) in nasopharynx and 13 (19.4%) in digestive system. Six patients were misdiagnosed by FDG PET/CT scan. FDG PET/CT could not detect the primary lesion in 66 patients, and three primary tumours were identified by conventional work-up after negative FDG PET/CT scan. The accuracy, sensitivity and specificity of FDG PET/CT scan in detecting the primary site in this study were 93.7%, 95.7% and 91.7%, respectively. FDG PET/CT scan changed the medical management of about 33.8% of 142 CUP patients.

CONCLUSION

FDG PET/CT whole-body imaging is a valuable tool in detecting the primary tumour of patients with CUP site.

Positron emission tomography in the detection of occult primary head and neck carcinoma: a retrospective study

Background

The management of cervical lymph node metastases from an unknown primary tumor remains a controversial subject. Recently, Positron Emission Tomography (PET) has proved useful in the detection of these tumors, even after an unsuccessful conventional diagnostic workup. This study was performed to assess the role of PET in the detection of occult primary head and neck carcinomas.

Methods

A retrospective analysis of a four year period at a tertiary referral oncology hospital was conducted.

Results

Of the 49 patients with cervical metastases of carcinoma from an unknown primary, PET detected a primary in 9 patients and gave 5 false positive and 4 false negative results. Detection rate, sensitivity, specificity and accuracy were of 18.4%, 69.2%, 86.1% and 81.6%, respectively. PET was also of substantial benefit in detecting distant metastatic disease and, thus, altered therapeutic strategies in a significant amount of patients.

Conclusions

Therefore, PET is a valuable tool in the management of patients with occult primary head and neck carcinoma, not only because it provides additional information as to the location of primary tumors, but also due to the fact that it can detect unexpected distant metastases.

Detection of primary sites in unknown primary tumors using FDG-PET or FDG-PET/CT

Background

Carcinoma of unknown primary tumors (CUP) is present in 0.5%-9% of all patients with malignant neoplasms; only 20%-27% of primary sites are identified before the patients die. Currently, 18F-fluorodeoxy-glucose positron-emission tomography (18F-FDG PET) or PET combined with computed tomography (PET/CT) is widely used for the diagnosis of CUP. However, the diagnostic yield of the primary site varies. The aim of this study was to determine whether PET or PET/CT has additional advantages over the conventional diagnostic workup in detecting the primary origin of CUP.

Findings

Twenty patients with unknown primary tumors that underwent PET or PET/CT were included in this study. For all patients, the conventional diagnostic workup was unsuccessful in detecting the primary sites. Among 20 patients, 11 had PET scans. The remaining nine patients had PET/CT. In all 20 patients, neither the PET nor PET/CT identified the primary site of the tumor, including six cases with cervical lymph node metastases. The PET and PET/CT revealed sites of FDG uptake other than those associated with known metastases in seven patients, but these findings did not influence patient management or therapy. Two patients had unnecessary invasive diagnostic procedures due to false positive results on the PET or PET/CT.

Conclusions

Although it is inconclusive because of small sample size of the study, the additional value of PET or PET/CT for the detection of primary sites in patients with CUP might be less than expected; especially in patients that have already had extensive conventional diagnostic workups. Further study is needed to confirm this finding.

Role of 18F-FDG PET in detecting primary site in the patient with primary unknown carcinoma

The aim of this study was to verify the effectiveness of positron emission tomography (PET) in detecting primary sites in carcinoma of unknown primary (CUP) patients. In this study, CUP represented a group of heterogeneous tumors that shared the clinical manifestation of metastatic carcinoma with no obvious primary site at the time of first diagnosis, which included clinical investigations, computed tomography, magnetic resonance imaging and panendoscopy. We reviewed the records of 24 patients with CUP between January 1995 and December 2009. The patients who demonstrated additional tracer uptake sites other than previously known metastatic lesions by PET scan were done direct biopsies for the sites of accumulation. Patients who had a negative PET scan or for whom the primary site could not be identified by direct biopsies underwent examination under anesthesia of the at-risk occult tumor sites. PET scan demonstrated focal accumulation suspicious for primary tumor in 12 (50.0%) of 24 patients: tonsil 5, nasopharynx 3, hypopharynx 1, tongue 1, larynx 1, and maxillary sinus 1. A subsequent biopsy of these sites revealed primary cancer in 9 (37.5%) of 24 patients: tonsil 5, nasopharynx 1, hypopharynx 1, tongue 1, and maxillary sinus 1. In the remaining three patients, no malignant cells were found by the biopsy of the accumulated area: nasopharynx 2, larynx 1. PET scans increase the yield of primary tumor by 37.5%. The sensitivity, specificity for PET scan were 80.8, 76.9%, respectively. PET scanning is useful in detecting primary cancer of CUP patients.

Ovarian mass mimicking malignancy: a case report

A 32-year-old female who suffered from abdominal pain underwent (18)F-fluorodexoyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for the diagnostic workup of pelvic mass lesions. Cystic mass lesions in the bilateral ovaries showed wall thickening and intense hypermetabolism along the rim. In addition, multifocal intense hypermetabolic lymphadenopathies were seen in the left paraaortic lymph node (LN), aortocaval LN, and both common iliac LNs. We interpreted these findings as bilateral ovarian cancer with retroperitoneal metastatic lymphadenopathies rather than endometriosis with reactive lymphadenopathies. However, histopathological examination confirmed the ovarian mass lesions as tubo-ovarian abscesses. We report a case that even if simultaneous hypermetabolic retroperitoneal LNs are seen, intense hypermetabolic lesions in both ovaries can be in consequence of inflammatory change.

Can diffusion-weighted imaging distinguish between normal and squamous cell carcinoma of the palatine tonsil?

The utility of diffusion-weighted imaging (DWI) in the detection of squamous cell carcinoma (SCC) of the tonsils has not been previously investigated. This preliminary study compared DWI of apparent SCC tonsillar tumours with normal tonsils. DWI of the tonsils was performed in 10 patients with newly diagnosed tonsil SCC that was evident on conventional MRI and in 17 patients undergoing cranial MRI for other indications. Regions of interest (ROI) were drawn around each identifiable tonsil on the apparent diffusion coefficient (ADC) map and the mean ADC value for each tonsil was calculated. ADC values for normal and SCC tonsils were compared using the Mann-Whitney U-test. The median ADC and range (x10(-3) mm(2) s(-1)) were found to be 0.814 and 0.548-1.312, respectively, for normal tonsils compared with 0.933 and 0.789-1.175, respectively, for SCC tonsils. ADC values were significantly higher for SCC tonsils than for normal tonsils (p = 0.009). No SCC tonsil had an ADC less than 0.82 x 10(-3) mm(2) s(-1) compared with 58% of normal tonsils. We conclude that there is a difference in the ADC between normal tonsils and SCC tonsils where the cancer is apparent on conventional MRI. These results are promising, although further studies are now required to determine whether DWI can be used to identify or exclude smaller foci of SCC within tonsils where the cancer is not evident on conventional MRI.

Fluorodeoxyglucose-positron-emission tomography imaging of head and neck squamous cell cancer

The hybrid technique of PET/CT has significantly impacted the imaging and management of HNSCC since its introduction in 2001 and has become the technique of choice for imaging of this cancer. Diagnostic FDG-PET/CT is useful for identification of an unknown primary tumor, delineation of extent of primary tumor, detection of regional lymph node involvement even in a normal-sized node, detection of distant metastases and occasional synchronous primary tumor, assessment of therapy response, and long-term surveillance for recurrence and metastases. The role of PET/CT is evolving in radiation therapy planning. Combined diagnostic PET/CT provides the best anatomic and metabolic in vivo information for the comprehensive management of HNSCC.

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.

Squamous Cell Carcinoma: Initial Diagnosis and Staging with PET/CT

Squamous cell carcinoma is the most frequent malignancy of the head and neck region, accounting for 5% of all malignant tumors worldwide. Accurate staging at diagnosis is critical for selection of appropriate treatment strategy. A variety of therapeutic options are used for treatment, including surgery with or without radical dissection, lymph node dissections of various severities, radiotherapy, chemotherapy, and combinations of these. Precise prediction of the extent of primary tumors, detection of unknown primary tumor, cervical lymph node status, and distant metastatic spread is important for treatment planning and prognosis. Accurate evaluation of these factors prior to treatment helps guide surgical extent or radiation porta, minimizing locoregional treatment failure.

Utility of combined (18)F-fluorodeoxyglucose-positron emission tomography and computed tomography in patients with cervical metastases from unknown primary tumors

(18)F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) has been reported to identify primary tumors in patients with cervical metastases from cancer of unknown primary (CUP). However, few reports have assessed the use of combined FDG-PET/computed tomography (CT) in this setting. We therefore examined the utility of combined FDG-PET/CT in the detection of primary tumors and unrecognized metastases in these patients. Patients with previously untreated CUPs underwent head and neck CT and whole-body FDG-PET/CT before panendoscopy and guided biopsy. The diagnostic accuracy of CT and FDG-PET/CT in detecting primary tumors and cervical metastases was compared with that of histopathology. The ability of FDG-PET/CT to detect distant metastases was also tested. Of the 44 eligible patients, 16 had occult primary tumors in the head and neck. FDG-PET/CT was significantly more sensitive than CT for detecting primary tumors (87.5% vs. 43.7%, P=.016), but their specificity did not differ (82.1% vs. 89.3%, P=.500). Thirty-four of 44 patients underwent neck dissection; 67 of 182 dissected cervical levels had metastatic nodal diseases. On a level-by-level basis, FDG-PET/CT was significantly more sensitive than CT (94.0% vs. 71.6%, P<.001), but the two methods were equally specific (94.8% vs. 96.5%). FDG-PET/CT correctly detected distant metastases in 6 of 6 patients. Combined FDG-PET/CT is a useful screening method for primary tumor detection, accurate nodal staging, and distant metastases in patients with CUPs.

New directions in head and neck imaging

Computerized tomography (CT) and magnetic resonance imaging (MRI), positron emission tomography (PET) and the hybrid modality of PET/CT are sensitive and reliable tools for detection and staging of head and neck cancers. This article describes the role of PET/CT in initial staging of head and neck squamous cell carcinoma, the utility of CT/MR perfusion imaging in qualitative analysis of tumor tissue, and the usefulness of diffusion weighted MR and dynamic contrast-enhanced MR imaging in head and neck oncological imaging.

Oral cavity cancer

The oral cavity is anterioly located and unique in the variety of tissues contained in this area. Although oral cancer screening may be done on clinical examination, imaging plays a critical role in staging and determination of deep margins for either tumor resectability or radiation planning. This article discusses the relevant anatomy on magnetic resonance imaging (MRI), including the lips and gingiva, floor of mouth, and oral tongue. This is followed by a discussion of standard MRI techniques, American Joint Committee on Cancer (AJCC) classification, and relevant MRI findings with discussion and imaging examples of carcinoma in major sites, including floor of mouth, oral tongue, buccal mucosa, bony upper alveolus, hard palate, and retromolar trigone. A brief summary of newer imaging techniques for evaluation of oral cancer is also presented.

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.

Positron emission tomography: poor sensitivity for occult tonsillar cancer

PURPOSE

The aim of the study was to determine the sensitivity of preoperative positron emission tomography (PET) scans in the detection of primary tumors of the tonsils.

MATERIALS AND METHODS

We conducted a retrospective review of 46 patients treated at a university medical center for occult tonsillar cancer during the years 2002 to 2004. We identified patients who underwent a preoperative PET scan to locate an unknown primary tumor. Fusion computed tomography with PET (PET/CT) was used to further delineate anatomic localization to the tonsil area. A positive PET/CT scan was defined as asymmetric increased tracer uptake in the tonsil and/or tonsillar fossa ipsilateral to the tonsillar cancer site when compared with the contralateral site. A negative PET/CT scan was defined as equivocal symmetric tracer uptake bilaterally.

RESULTS

Of the 46 patients, 6 (13.0%) had pretreatment PET scans. Of these 6 patients, 16.7% (n = 1) had positive PET, 66.7% (n = 4) had negative PET, and 16.7% (n = 1) demonstrated increased tracer uptake in tonsils bilaterally greater on the side contralateral to the cancer. In this group, PET scans had a sensitivity of 0.167 and false-negative ratio of 0.667 for tonsillar cancer detection.

CONCLUSIONS

Although the patient population in this study is small (n = 6), the findings suggest that PET/ CT scans may offer a low sensitivity in detection of primary tonsillar cancers. However, PET/CT scans still have a significant role in the detection of other unknown primary head and neck tumors. Technical reasons for this finding are discussed.

Management of cancer from an unknown primary

Treatment of cancer is reliant on identifying the organ of origin. However, in a significant minority of cases, the primary site is never identified. This paper reviews the diagnostic work-up and therapeutic management for patients presenting with unknown primary cancer, including the role of tumour markers, conventional pathology and positron emission tomography imaging. It is important to identify atypical presentations of known tumour types, such as extragonadal germ cell tumours, lymphomas and breast cancer. The results from chemotherapy trials performed in patients with unknown primary cancer are summarised. Few trials have included > 100 patients, and most are non-randomised. There is no clear standard of care from the available data, and no trials of chemotherapy versus best supportive care have been performed. Platinum is the mainstay of treatment regimens, and from the regimens tested, a taxane seems to be among the best of the cytotoxics to combine with platinum in terms of both tolerability and efficacy. There is no data to favour a three-drug combination over a two-drug combination. To improve on existing treatment, molecular techniques may provide a means to identify the organ of origin, and/or to select appropriate targeted therapies. Further research is needed to improve knowledge on the biology of cancer from an unknown primary and to develop more effective treatment.

[Positron emission tomography in head and neck squamous cell carcinomas]

18F-Fluorodeoxyglucose positron emission tomography (PET) is an imaging modality which is becoming increasingly esential in oncology, especially in the management of head and neck squamous cell carcinomas (SCC). The most common uses of the PET are listed in this thematic study: initial staging, cervical lymph node metastases from an unknown primary tumor and post-therapeutic follow-up. The advantages and drawbacks of this imaging tool are exposed here according to both our experience and data from the literature. Decision schemes are suggested for each use so as to optimize the use of this imaging modality in the management of these SCC. Other fields of application for the PET are mentioned, such as the in-progress evaluation of response to chemotherapy, the interest of this imaging tool in radiotherapy as well as current biochemical developments concerning new tracers.

Fusão de imagens PET-TC na avaliação do carcinoma espinocelular de cabeça e pescoço

OBJETIVO: Os autores estabeleceram uma metodologia para avaliar carcinoma espinocelular de cabeça e pescoço, identificando e distinguindo áreas de grande atividade metabólica dentro da neoplasia, associando dados simultaneamente adquiridos, obtidos por diferentes modalidades de aquisição de imagens, combinando informações metabólicas e anatômicas num único exame. MATERIAIS E MÉTODOS: A população estudada consistiu de 17 pacientes com carcinoma espinocelular pertencentes aos arquivos do Departamento de Imagem do Hospital do Câncer, São Paulo. As imagens de tomografia computadorizada (TC) e da tomografia por emissão de pósitrons (PET) com 2-[F-18]-fluoro-2-deoxi-d-glucose (18F-FDG-PET) foram simultaneamente adquiridas utilizando aparelho não dedicado. Os dados originais foram transferidos para uma estação de trabalho independente com o programa Entegra 2NT para gerar a fusão de imagens da PET e TC. RESULTADOS: Os achados foram definidos como positivos na presença de focos com aumento da concentração do radiofármaco em áreas não relacionadas à sua distribuição normal. CONCLUSÃO: A fusão de imagens simultaneamente adquiridas num único exame (18F-FDG-PET e TC) possibilitou o mapeamento topográfico metabólico das lesões estudadas e foi possível localizar áreas de maior atividade metabólica dentro do próprio tumor, verificando recidivas ou metástases, possibilitando aumentar as opções quanto ao planejamento radioterápico ou cirúrgico.

PET in face and neck tumours

FDG-PET is a useful tool in the imaging of head and neck tumours. It can be used to stage the primary tumour, to assess response to therapy and most importantly for the detection of recurrent tumour. The advantages and limitations of this technique are discussed in this article.

[Contribution of 18-F-FDG PET for detection of head and neck carcinomas with an unknown primary tumor]

OBJECTIVES

To evaluate the usefulness of fusioning positron emission tomography with computed tomography (PET/CT) for the detection of head and neck carcinomas of unknown primary.

METHODS

This prospective study included 20 patients with cervical lymph node of squamous cell carcinoma of unknown primary after standard initial workup (nasofibroscopy and CT scan of the chest and head and neck). Patients underwent PET/CT and panendoscopy of the upper airways and upper digestive tract with PET/CT directed biopsies. The follow-up was 6 months minimum in all patients.

RESULTS

A potential primary tumor was found in 10 of the 20 cases and confirmed by histology in 7 cases (3 bases of tongue, 1 tonsillar pillar, 1 vallecula, 1 tonsillar fossa, 1 piriform sinus). Four of these seven patients presented a normal endoscopy (diagnosis was made with submucosal PET/CT directed biopsies). PET/CT was normal in 10 of 20 cases with 3 false negatives. The sensitivity of PET/CT was 70%, the specificity was 70% and the accuracy was 70%.

CONCLUSION

PET/CT seems to be of interest in the detection of head and neck carcinoma of unknown primary. PET/CT detected 15% of unknown primary tumors with treatment-related implications.

Evaluation of the impact of addition of PET to CT and MR scanning in the staging of patients with head and neck carcinomas

The addition of whole body positron emission tomography (PET) to the investigation of patients with newly diagnosed head and neck squamous cell carcinoma (HNSCC) was assessed over a 6-month period. Staging investigations included laryngoscopy, oesophagoscopy, CXR, CT and MRI. In addition, all patients had an extended-field (whole body) FDG-PET scan and were restaged. Standardised Uptake Values (SUV) were used to measure FDG uptake. SUV levels above 5 were considered indicative of the presence of tumour, values below 3 indicative of benign aetiology and values equal to and between 3 and 5 were considered equivocal. Forty-eight consecutive patients with biopsy proven HNSCC were included for study. Three patients presenting with neck disease had unknown primary tumours. Of the remaining 45 patients, CT scan correctly identified 40 of the primary tumours (89%). MRI and PET both identified 41 primary tumours (91%). Thirty-two patients underwent neck dissection. Of these patients 12 had pathologically N0 necks and 20 had positive nodal disease. CT scan and MRI each correctly staged pN0 necks in 10 of 12 patients (83%) whereas PET alone had a lower true negative rate of 8 out of 12 patients (67%). PET correctly staged the N+ necks in 14/20 patients (70%) versus 12/20 (60%) for MRI, and 8/20 (40%) for CT alone. All four patients who were judged to have distant metastases by PET had these metastases deemed negative by other investigation. None of the three imaging modalities was able to identify the tumour site in the three patients with unknown primaries. In conclusion, although PET has got a higher sensitivity in detecting nodal disease, it has only slightly improved the classification of N+ necks. The findings of this study cast doubt on the merit of routine addition of PET to the current investigative protocols for HNSCC patients.

The current status of positron-emission tomography scanning in the evaluation and follow-up of patients with head and neck cancer

PURPOSE OF REVIEW

Functional imaging has increasingly become an important diagnostic tool for head and neck cancer and as its availability increases so will its utilization. Positron-emission tomography using the radiotracer [18F]fluoro-2-deoxy--glucose is the most commonly used functional imaging technology and it has the potential to improve the staging and detection of head and neck tumors compared with conventional imaging techniques such as computed tomography or magnetic resonance imaging.

RECENT FINDINGS

The combination of [18F]fluoro-2-deoxy--glucose and positron-emission tomography contributes valuable information in localizing a primary tumor in patients with an unknown primary and neck metastases, in the staging of primary head and neck cancer, in the detection of residual disease following definitive chemoradiation, and in the detection of recurrent disease. New technologies have been recently introduced using the combination of computed tomography and positron-emission tomography that allows exact anatomical correlation with areas of increased tracer uptake. In addition, new tracers may allow quantification of important cellular processes related to tumor proliferation or identification of tumors that may respond to certain targeted therapies.

SUMMARY

[18F]Fluoro-2-deoxy--glucose and positron-emission tomography are increasingly being used as a clinical imaging modality in the complex management of head and neck cancer. In particular, its clinical value in the evaluation of the unknown primary, and the evaluation of recurrent or residual disease, is well established and has shown to be more accurate than conventional imaging modalities.