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

The radiological unknown primary of the head and neck: Recommendations for imaging strategies based on a systematic review

OBJECTIVES

To develop recommendations for the radiological investigation of clinically occult primary cancer in the head and neck.

DESIGN AND SETTING

In accordance with PRISMA guidelines, a search was performed on Medline, Embase and Cochrane library databases to investigate the efficacy of ultrasound guided Fine Needle Aspiration (US FNAC), contrast enhanced CT (CECT), magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose PET-CT (18F-FDG PET-CT) in the investigation of head and neck squamous cell carcinoma from an unknown primary (HNSCCUP) presenting with a metastatic cervical lymph node (s). The Quality Assessment of Diagnostic Accuracy Studies Version 2 tool and SIGN 50 guidelines were used to assess the risk of bias and quality of the included studies.

PARTICIPANTS

Adult patients presenting with metastatic cervical lymph nodes from a HNSCCUP.

MAIN OUTCOME MEASURES

Utility of different imaging modalities (PET-CT, MRI, CE CT and US FNAC in the management of HNSCCUP).

RESULTS

Twenty-eight studies met inclusion criteria; these were meta-analyses, systematic reviews, prospective and retrospective studies.

CONCLUSIONS

The optimal imaging strategy involves utilisation of various imaging modalities. US FNAC can provide the initial diagnosis and HPV status of the occult primary tumour. CECT and MRI detect up to 44% of occult tumours and guide management. FDG PET-CT is the most sensitive imaging modality for the detection of CUP and should be performed prior to panendoscopy.

Advancement in the Oropharyngeal Primary Unknown Cancer Diagnostic and Current Treatments Pathway: A Narrative Review

Objective: The objective of this article is to define a correct diagnostic pathway for oropharyngeal cancer of unknown primary (OPCUP) identification. Background: OPCUP represents one of the most frequent causes of neck metastases onset without the identification of the primary tumor. Therefore, there is a high percentage of late or missing diagnoses, resulting in treatment delay or in a wrong therapeutic process. The up-to-date diagnostic procedures can help us to begin therapies at the right time. Methods: This is a review of the latest articles about diagnostic pathways in the OPCUP. A selection of the references was carried out in PubMed, EMBASE, Cochrane, and CENTRAL electronic databases. Conclusion: The oropharynx represents the most common site of primary unknown head and neck cancer (HNCUP). Recent epidemiologic data reported an increasing incidence of HNCUP related to human papilloma virus positive squamous cell carcinoma. Positron emission tomography combined with computerized tomography scanning or magnetic resonance imaging allows for improving the detection of primary unknown tumors and distant and locoregional metastases. Finally, the introduction of the trans-oral robotic surgical approach has introduced a new role of surgery in the HNCUP diagnosis and treatment. Hence, the new technological improvement allows reaching in most HNCUP patients an early diagnosis, achieving targeted management and better treatment outcomes, as well as decreasing toxicity and the side effects of treatment options.

Impact of 18F-Fluorodeoxyglucose positron emission tomography on management of cancer of unknown primary: systematic review and meta-analysis

BACKGROUND

Cancers of unknown primary (CUP) have traditionally been treated empirically, with a dismal prognosis. Compared with standard diagnostic tests, including CT and MRI, imaging with ¹⁸F-fluorodeoxyglucose (FDG) PET or PET/CT has shown the capacity to better identify the primary tumour site and detect additional sites of metastasis. However, its clinical impact is not well established. We performed a systematic review and meta-analysis of prior studies to assess the impact of FDG-PET or PET/CT on the management of patients with CUP.

MATERIALS AND METHODS

Pubmed and EMBASE databases were searched up to 4th February 2021. Studies that reported the proportion of patients with CUP who experienced a management change after FDG-PET or PET/ computed tomography (CT) were included and the proportions were pooled using the random-effects model. Study quality was assessed using QUADAS-2. Subgroup analysis was conducted to explore heterogeneity.

RESULTS

Thirty-eight studies (involving 2795 patients) were included. The pooled proportion of patients with management changes was 35% (95% confidence interval 31%-40%). There was substantial heterogeneity among the studies (Q-test, p < 0.01; I² = 82%). The specific reason for management change was more commonly detection of the primary site (22% [95% CI 18-28%]) than detection of additional metastatic sites (14% [95% CI 10-19%]). The pooled proportions of patients with management changes were similar among numerous subgroups (range, 32.8%-38.2%).

CONCLUSION

FDG-PET or PET/CT had a meaningful impact on the management of patients with CUP. Approximately, a third of patients had their management changed because of FDG-PET or PET/CT results, and this finding was consistent across numerous subgroups.

The emerging role of trans-oral robotic surgery for the detection of the primary tumour site in patients with head-neck unknown primary cancers: A meta-analysis

The identification of the site in head neck unknown primary (HNUP) tumour is of utmost importance to help select best treatment while decreasing treatment-related morbidity and mortality. The primary purpose of this study is to demonstrate that TORS may be a valuable tool in detecting primary tumour. Studies were systematically searched in the PubMed, EMBASE, the Cochrane Library and CENTRAL electronic databases. A total of 12 selected studies (349 patients) were analyzed. The primary tumour detection and positive surgical margins rates were 70.8% and 19.4%, respectively. The rate of HPV-related tumour was 71.3%. The primary tumour was mainly in base of tongue (64%). In conclusion, TORS seems to be an effective surgical approach both in terms of detection of primary tumour site and in terms of therapeutic perspective for HNUP. In particular, a subset of HPV-related tumours might benefits all advantages from this surgical modality.

Efficacy of 18F-FDG PET/CT in investigation of elevated CEA without known primary malignancy

Aim:

To evaluate the efficacy of ¹⁸flurodeoxyglucose positron emission tomography/computer tomography (¹⁸F-FDG PET/CT) in investigating patients with elevated carcinoembryonic antigen (CEA) and without known primary malignancy, and the impact of PET/CT findings on patient management.

Setting and Design:

PET/CT scans done in a tertiary hospital between December 2007 and February 2012 for elevated CEA in patients without known primary malignancy were retrospectively reviewed.

Materials and Methods:

The PET/CT findings, patients' clinical information, level of CEA, histological diagnosis, and subsequent management were retrieved by the electronic patient record for analysis.

Statistical Analysis:

Data were analyzed using SPSS version 19.

Results:

One hundred and one PET/CT scans were performed for patients with elevated CEA. Fifty-eight of these were performed for patients with known primary malignancy and were excluded; 43 PET/CT scans were performed for patients without known primary malignancy and were included. Thirty-three (77%) had a positive PET/CT. Among the 32 patients with malignancy, 15 (47%) suffered from lung cancer and 8 (25%) suffered from colorectal cancer. The sensitivity (97%), specificity (82%), positive predictive value (94%), negative predictive value (90%), and accuracy (93%) were calculated. Thirty (91%) patients had resultant change in management. The mean CEA level for patients with malignancy (46.1 ng/ml) was significantly higher than those without malignancy (3.82 ng/ml) (P < 0.05). In predicting the presence of malignancy, a CEA cutoff at 7.55 ng/ml will achieve a sensitivity of 91% and a specificity of 73%.

Conclusion:

PET/CT, in our study population, appears to be sensitive, specific, and accurate in investigating patients with elevated CEA and without known primary malignancy. In addition to diagnosis of underlying primary malignancy, PET/CT also reveals occult metastases which would affect patient treatment options. Its role in investigating patients with elevated CEA and without known primary, compared with other investigation modalities, remains to be studied.

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.

Positron Emission Tomography in Head and Neck Squamous Cell Carcinoma of Unknown Primary

This article summarizes selected published studies on the use of FDG-PET and PET/CT in the workup of head and neck carcinoma of unknown primary (HNCUP). It shows that PET is a useful imaging modality in identification of the occult primary tumor and discovery of distant metastases. The results of PET often lead to a change in management in these patients. The limitations of PET in HNCUP are also discussed.

The role of transoral robotic surgery, transoral laser microsurgery, and lingual tonsillectomy in the identification of head and neck squamous cell carcinoma of unknown primary origin: a systematic review

BACKGROUND

Squamous cell carcinoma of the head and neck can present as a cervical metastasis from an unknown primary site. Recently, transoral robotic surgery (TORS) and transoral laser microsurgery (TLM) have been incorporated in the workup of unknown primary tumors.

METHODS

We searched MEDLINE, EMBASE, Cochrane, and CINAHL from inception to June 2015 for all English-language studies that utilized TORS, TLM, or lingual tonsillectomy in the approach to an unknown primary.

RESULTS

Of 217 identified studies, eight were reviewed. TORS/TLM identified the primary tumor in 111/139 (80 %) patients overall, and 36/54 (67 %) patients with no remarkable findings following physical exam, radiologic imaging, and panendoscopy with directed biopsies. Lingual tonsillectomy identified the primary tumor in 18/25 (72 %) patients with no findings. Hemorrhage (5 %) was the most common perioperative complication.

CONCLUSION

Lingual tonsillectomy using new approaches such as TORS/TLM may improve the identification of occult primary tumors.

Cervical lymphadenopathy: study of 251 patients

Correct diagnosis of cervical lymphadenopathy is often a great challenge. The objective of this case study is to describe the distribution of the most common causes of unclear neck swellings presented in an ENT-Department and to evaluate the clinical history, examination and laboratory findings. In a retrospective study at the Department of Otorhinolaryngology, University Medical Center Homburg/Saar, 251 patients were enrolled with clinical and ultrasound signs of cervical lymphadenopathy as well as lymph node extirpation for histopathological evaluation. 127 patients (50.6 %) had a histological malignant finding. The distribution of the most common pathological conditions was as follows: Non-specific reactive hyperplasia n = 89 (35.5 %), metastases n = 86 (34.3 %), lymphoma n = 41 (16.3 %), granulomatous lesions n = 15 (6 %), abscess formations n = 5 (2 %), necrotic lymphadenitis and Castleman's disease one case of each, lymph node with normal architecture n = 7 (2.8 %), and neck masses mimicking lymphadenopathy n = 6 cases (2.4 %). The following factors identified by multivariate logistic regression were significantly associated to malignant lymphadenopathy: increasing age, generalized lymphadenopathy and history of malignant disorder, fixed neck masses and increasing diameter in ENT examination, bulky lesion, absence of hilus, blurred outer contour, protective role of the long form and decreasing Solbiati-index values by ultrasound B-Mode gray scale examination. Level II contained more benign lymphatic lesions, while the malignancy rate in level IV and V was enhanced. Laboratory parameters significantly associated to malignancies were CRP, LDH and thrombocytopenia. Patients with persisting cervical lymphadenopathy and over 3 weeks of antibiotic treatment should be considered for early biopsy, especially if some of the risk factors, pointed out in this study, are present.

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.

Prognostic value of pretreatment 18F-FDG PET/CT parameters including visual evaluation in patients with head and neck squamous cell carcinoma

OBJECTIVE

The purpose of this study was to determine whether pretreatment quantitative and visual parameters seen on PET/CT using (18)F-FDG add prognostic information for clinical staging in patients with head and neck cancer.

MATERIALS AND METHODS

We enrolled 108 patients with histologically proven oral, oropharyngeal, hypopharyngeal, and laryngeal squamous cell carcinomas who underwent FDG PET/CT before treatment and, later, definitive therapy in our study. PET/CT parameters-maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and uptake pattern (sphere-shaped or ring-shaped)-were recorded. The prognostic value of these parameters was evaluated using univariate and multivariate Cox regression analyses.

RESULTS

In the univariate analysis, all of the FDG PET/CT parameters--SUVmax (> 10 g/mL) of the primary tumor, MTV (> 20 cm(3)), TLG (> 70 g), and uptake pattern (ring-shaped)--were significantly associated with negative effects on disease-specific survival (DSS) and disease-free survival (DFS). In the multivariate analysis, the MTV and uptake pattern remained associated with DSS after corrections for the Union for International Cancer Control (UICC) stage and definitive therapy (p = 0.023 and < 0.001, respectively). Another multivariate model that included MTV as a continuous variable, uptake pattern, and UICC stage showed that the uptake pattern remained significantly associated with DSS, whereas the association between DSS and MTV was not significant (p < 0.001 and = 0.332, respectively).

CONCLUSION

Our data indicate that the pretreatment PET/CT parameters had prognostic value. In particular, a qualitative factor, uptake pattern, provided better prognostic information to the clinical staging of head and neck squamous cell carcinomas than the other PET/CT parameters.

Utility of quantitative 18 F-fluorodeoxyglucose uptake measurement to identify occult tonsillar carcinoma in patients with cervical metastasis of unknown primary tumours: a retrospective case-control study

OBJECTIVES

Due to relatively high (18) F-fluorodeoxyglucose accumulation in the tonsillar region, the detection of occult tonsillar cancers by (18) F-fluorodeoxyglucose positron emission tomography/computerised tomography remains controversial. Therefore, we assessed the usefulness of quantitative tonsil (18) F-fluorodeoxyglucose uptake in identifying occult tonsillar squamous cell carcinoma.

DESIGN

A case-control study of retrospective cohorts.

SETTING

University Teaching Hospital.

MAIN OUTCOME MEASURES

We assessed all patients diagnosed with tonsillar cancers or cervical lymph node metastasis of unknown primary tumours between 2005 and 2010 who underwent (18) F-fluorodeoxyglucose positron emission tomography/computerised tomography. The subjects were grouped into A (apparent early pT-stage tonsillar squamous cell carcinoma; n = 27), B (occult tonsillar squamous cell carcinoma, primary tumours were found by surgery; n = 21), C (cervical metastasis of unknown primary tumour, primary tumours were not found by surgery and for follow-up; n = 16) and D (33 healthy controls). Tonsillar maximum standardised uptake values were bilaterally measured and compared between groups.

RESULTS

The sensitivity and specificity of qualitative assessment of (18) F-fluorodeoxyglucose positron emission tomography/computerised tomography for detection of occult tonsillar cancers were 67% and 69%, respectively. Mean maximum standardised uptake values of tonsils with cancer were 11.19 ± 5.46 in group A and 8.12 ± 4.52 in group B, which were significantly higher than that of group C (4.62 ± 1.76) or group D (4.57 ± 1.62) (P < 0.01). The mean maximum standardised uptake value differences of groups A (6.35) and B (3.11) were significantly greater than those of groups C (0.32) and D (0.59) (P < 0.01). Similarly, the mean maximum standardised uptake value ratios of groups A (2.47) and B (1.73) were significantly greater than those of groups C (1.06) and D (1.16) (P < 0.01).

CONCLUSION

(18) F-fluorodeoxyglucose positron emission tomography/computerised tomography with tonsil SUVmax measurement is useful to identify occult tonsillar squamous cell carcinoma.

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.

Clinical features of HPV-related head and neck squamous cell carcinoma: presentation and work-up

Head and neck squamous cell carcinoma (HNSCC) that arises as a result of the activity of human papillomavirus (HPV) malignant transformation has a distinct disease pattern that is the basis for its clinical presentation. A clear understanding of these distinct clinical features enables diagnosticians to maintain awareness and index of suspicion to avoid delays in detection and select the most effective and thorough measures of evaluating the disease and directing treatment selection. Attention is focused on the broader demographic at risk for developing HPV-related HNSCC, the phenomenon of cystic cervical nodal metastases, and the unknown or occult primary cancer.

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 as an effective diagnostic workup in cervical metastasis of carcinoma from an unknown primary tumor

PURPOSE

The purpose of this study is to assess the potential of ¹⁸F-fluorodeoxyglucose (¹⁸FDG) positron emission tomography/computed tomography (PET/CT) imaging for the diagnosis of cervical metastasis of carcinoma of an unknown primary tumor (CUP) and to determine whether the maximum standardized uptake value (SUV(max)) is a prognostic factor.

METHODS

Twenty-five consecutive patients with cervical metastasis of CUP were retrospectively analyzed by PET/CT between July 2007 and July 2011.

RESULTS

FDG PET/CT suggested a primary tumor in 21 out of 25 patients (84.0%). The sensitivity of FDG PET/CT in detecting the primary tumor was 73.3% (11 of 15), and the positive predictive value was 52.4% (11 of 21). The median follow-up duration of survival patients was 10.4 months (range: 0-30 months). The estimated 2-year overall survival rate of all patients was 50.0%. Univariate analyses did not reveal a significant difference in overall survival between the group of 11 patients identified by pathology and the 14 patients not identified by pathology (overall survival was 57.1% and 49.1%, respectively; p=0.468). The median SUV(max) was 7.6. In the log-rank test, patients with a low SUV(max) (≤ 7.0) in cervical lymph nodes had a significantly higher survival rate at 2 years (87.5% vs. 21.2%; p=0.007) than patients with a high SUV(max) (>7.0).

CONCLUSIONS

Although our study was inconclusive due to the small sample size, our results suggest that FDG PET/CT may be an effective diagnostic workup in the cervical metastasis of carcinoma from an unknown primary tumor (UPT). In the present study, SUV(max) of PET/CT in the cervical lymph node may serve as a prognostic factor of cervical metastasis of carcinoma from a UPT based on the limited number of patients. Further studies are needed to confirm these findings.

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.

Lymph node metastasis of squamous cell carcinoma from an unknown primary in the upper and middle neck: Impact of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography

PURPOSE

The purpose of this study was to assess the potential of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) imaging for detection of the primary tumor and its impact on treatment planning in patients presenting with cancer of unknown primary and squamous cell carcinoma (SCC)-positive cervical lymph nodes of the upper and middle neck.

METHODS

The study population consisted of 18 consecutive patients with biopsy-proven SCC involving lymph nodes of the upper and middle neck region and negative conventional diagnostic procedures with regard to the location of the primary. All patients underwent FDG-PET/CT according to a standard procedure in search for the primary, unidentified tumor.

RESULTS

In none of the patients FDG-PET/CT was able to indicate a primary tumor localization. Although FDG-PET/CT did identify all sites of known lymph node involvement, neither additional sites of lymph node involvement nor sites of distant metastases were identified. Accordingly, FDG-PET/CT did not impact patient treatment planning.

CONCLUSIONS

In this series, including patients suffering from lymph node metastases by an SCC of unknown primary in the upper and middle neck, FDG-PET/CT was unable to identify a primary tumor. In addition, FDG-PET/CT did not modify the treatment planning in any of the patients studied.

Sequential FDG-PET/CT after neoadjuvant chemotherapy is a predictor of histopathologic response in patients with head and neck squamous cell carcinoma

PURPOSE

To evaluate whether 2-deoxy-2-[(18)F]fluoro-D-glucose positron emission tomography/computed tomography (FDG-PET/CT) more accurately predicts the histopathologic response to neoadjuvant chemotherapy (NAC) than magnetic resonance imaging (MRI) in patients with head and neck squamous cell carcinoma (HNSCC).

PROCEDURES

Sixteen patients with HNSCC underwent FDG-PET/CT and MRI scans before and after one cycle of NAC, followed by surgical resection. The 26 surgically resected specimens of the 16 patients were analyzed. Decreases in maximum standardized uptake value (SUV(max)) or in tumor maximum size (diameter(max)) were calculated, and their accuracies for the prediction of histopathologic response were evaluated.

RESULTS

In histopathologic responders (n = 7), percent decreases in SUV(max) were significantly higher (P < 0.001) than in non-responders (n = 19). Applying a cut-off point of 55.5%, the histopathologic response could be predicted with a sensitivity and specificity of 86% and 95%, respectively.

CONCLUSION

FDG-PET/CT can predict histopathologic NAC responses with higher accuracy than MRI in HNSCC patients.

PET and PET/CT for unknown primary tumors

Carcinoma of unknown primary (CUP) is defined as histologically proven metastatic disease that, after a complete diagnostic work-up, yields no primary detectable tumor. CUP is one of the ten most frequent cancers, with overall poor outcome. Detection of the unknown primary tumor is of crucial importance in this scenario, since it might help to select and offer definitive treatment, which, in turn, may improve patient prognosis. Additional diagnostic work-up, usually consisting of a combination of several radiological and endoscopic investigations and serum tumor marker studies, can be time consuming, expensive, and pose a significant burden to the patient. The final diagnostic yield of these tests is often limited. Combined positron emission tomography/computed tomography (PET/CT), using the radiotracer (18)F-fluoro-2-deoxyglucose (FDG), may be of great value in the management of patients with CUP for the detection of primary tumors. This chapter gives a brief introduction to the syndrome of CUP, followed by an outline of the rationale, use, and utility of FDG-PET/CT in CUP, and concludes with a discussion on the challenges and future directions in the diagnostic management of patients with CUP.

Unknown primary tumors

An unknown primary tumor (UPT) is defined by the presence of a metastatic cancer without a known primary site of origin despite a standardized diagnostic workup. Clinically, UPTs show rapid progression and early dissemination, with signs and symptoms related to the metastatic site. The molecular bases of their biology remain largely unknown, with no evidence as to whether they represent a distinct biological entity. Immunohistochemistry remain the best diagnostic tool in term of cost-effectiveness, but the time-consuming "algorithmic process" it relies on has led to the application of new molecular techniques for the identification of the primary site of UPTs. For example, several microarray or miRNA classifications of UPTs have been used, with an accuracy in the prediction of the primary site as high as 90%. It should be noted that validating a prediction of tissue origin is challenging in these patients, since most of them will never have a primary site identified. Moreover, prospective studies to determine whether selection of treatment options based on such profiling methods actually improves patient outcome are still missing. In the last few years functional imaging (i.e. FDG-PET/CT) has gained a main role in the detection of the site of origin of UPTs and is currently recommended by the European Association of Nuclear Medicine. However, despite recent refinements in the diagnostic workup, the site of origin of UPT often remains elusive. As a consequence, treatment of patients with UPT is still empirical and inadequate.

Clinical utility of PET/CT in the evaluation of head and neck squamous cell carcinoma with an unknown primary: a prospective clinical trial

BACKGROUND

Metastatic head and neck squamous cell carcinoma with an unknown primary is an uncommon but important problem. PET/CT, as an adjunct to diagnosis, is potentially useful but has never been studied in a prospective, single-blinded clinical trial.

METHODS

In all, 20 subjects with cervical metastases from an unknown head and neck primary were enrolled in a prospective clinical trial. A standard protocol was used in both clinic and operating room (OR). Study surgeons were blinded to the PET/CT result upon completion of the standard work-up.

RESULTS

PET/CT increased the detection of a primary site from 25% to 55% (5 vs 11 subjects). This difference was statistically and clinically significant (p = .03, McNemar's test). There was 1 false negative PET/CT scan.

CONCLUSIONS

An unknown primary should be diagnosed only after a complete head and neck examination, flexible endoscopy, and CT or MRI. PET/CT performed prior to panendoscopy will increase the diagnostic yield in the unknown head and neck primary population, leading to more targeted, and less morbid, treatment.

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.

Diagnosis and treatment of a neck node swelling suspicious for a malignancy: an algorithmic approach

Aim. To present an up-to-date algorithm incorporating recent advances regarding its diagnosis and treatment. Method. A Medline/Pubmed search was performed to identify relevant studies published in English from 1990 until 2008. Only clinical studies were identified and were used as basis for the diagnostic algorithm. Results. The eligible literature provided only observational evidence. The vast majority of neck nodes from occult primaries (>90%) represent SCC with a high incidence among middle aged man. Smoking and alcohol abuse are important risk factors. Asiatic and North African patients with neck node metastases are at risk of harbouring an occult nasopharyngeal carcinoma. The remainder are adenocarcinoma, undifferentiated carcinoma, melanoma, thyroid carcinoma and Merkel cell carcinoma. Fine needle aspiration cytology (FNAC) reaches sensitivity and specificity percentages of 81% and 100%, respectively and plays an important role as the second diagnostic step after routine ENT mirror and/or endoscopic examination. FDG-PET/CT has proven to be helpful in identifying occult primary carcinomas of the head and neck, especially when applied as a guiding tool prior to panendoscopy, and may induce treatment related clinical decisions in up to 60% of cases. Conclusion. Although reports on the diagnostic process offer mainly descriptive studies, current information seems sufficient to formulate a diagnostic algorithm to contribute to a more systematic diagnostic approach preventing unnecessary steps.

Hybrid imaging (SPECT/CT and PET/CT): improving therapeutic decisions

The incremental diagnostic value of integrated positron emission tomography-computed tomography (PET/CT) or single-photon emission computed tomography (SPECT)/CT images compared with PET or SPECT alone, or PET or SPECT correlated with a CT obtained at a different time includes the following: (1) improvement in lesion detection on both CT and PET or SPECT images, (2) improvement in the localization of foci of uptake resulting in better differentiation of physiological from pathologic uptake, (3) precise localization of the malignant foci, for example, in the skeleton vs soft tissue or liver vs adjacent bowel or node (4) characterization of serendipitous lesions, and (5) confirmation of small, subtle, or unusual lesions. The use of these techniques can occur at the time of initial diagnosis, in assessing the early response of disease to treatment, at the conclusion of treatment, and in continuing follow-up of patients. PET/CT and SPECT/CT fusion images affect the clinical management in a significant proportion of patients with a wide range of diseases by (1) guiding further procedures, (2) excluding the need of further procedures, (3) changing both inter- and intramodality therapy, including soon after treatment has been initiated, and (4) by providing prognostic information. PET/CT fusion images have the potential to provide important information to guide the biopsy of a mass to active regions of the tumor and to provide better maps than CT alone to modulate field and dose of radiation therapy. It is expected that the role of PET/CT and SPECT/CT in changing management will continue to evolve in the future and that these tools will be fundamental components of the truly "personalized medicine" we are striving to deliver.

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.

[Positron emission tomography/computed tomography in patients with cancer of unknown primary origin]

Cancer of unknown primary origin is not an uncommon clinical state, usually accounting for 2%-7% of all cancer patients.

MATERIAL AND METHODS

Positron emission tomography and computed tomography (PET/CT) was performed in 17 patients with histologically proven metastatic tumors of unknown primary and negative or inconclusive conventional diagnostic procedures.

RESULTS

The study included 17 patients (8 male and 9 female) age from 42 to 76 years. PET / CT has pointed out the probable localization of primary tumors in 10 patients. According histological diagnosis of carcinoma of unknown origin, most common is adenocarcinoma (64.71%). Origin of the primary cancer was found in 72.73% patients with adenocarcinoma 66.67% of respondents with squamocelular carcinoma and 50% of respondents with low differentiated carcinoma. Location of primary cancer was not found in 41.18% of the respondents, including patients with mucinous adenocarcinoma and patients with melanoma.

CONCLUSION

FDG PET/CT demonstrates very good whole-body imaging method in evaluation of patients with unknown primary carcinoma.

Best practices in PET/CT: consensus on performance of positron emission tomography-computed tomography

Positron emission tomography-computed tomography (PET-CT) using the glucose metabolism tracer 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) has become a widespread and preferred imaging modality for evaluating most cancers. Since commercial PET-CT scanners became available in 2001, there has been rapid dissemination of this hybrid imaging modality and PET-CT scanners have largely replaced stand-alone PET scanners. How PET-CT scans are performed and applied to cancer management has varied considerably, in part reflecting the varied background of the practice settings and training experience of the physicians performing and interpreting the PET-CT studies. Combined PET/CT with FDG has become the gold standard in oncologic imaging by accurately defining anatomy and function of many tumors. From April 2-4, 2008, a focus group composed of physicians and technologists from different practice settings and training backgrounds entitled "Best Practices in PET/CT Symposium" was held in Sonoma, California. The symposium focused on optimization of PET-CT protocols but also included other pertinent topics related to PET-CT imaging in oncology. This article summarizes areas of consensus reached by the group regarding many of the discussion topics. The summary consensus covered in this article is meant to provide direction for future discussions on how to improve the application of this hybrid modality to patient care.

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 FDG PET/CT: Utility and Applications in Clinical Oncology

Accurate diagnosis and staging are essential for an optimal management of cancer patients. Positron emision tomography with 2-deoxy-2-fluorine-18-fluoro-D-glucose (¹⁸FDG-PET) and, more recently, ¹⁸FDG-PET/computed tomography (¹⁸FDG-PET/CT) have emerged as powerful imaging tools in oncology, because of the valuable functional information they provide. The combined acquisition of PET and CT has synergistic advantages over its isolated constituents and minimizes their limitations. It decreases examination times by 25%–40%, leads to a higher patient throughput and unificates two imaging procedures in a single session. There is evidence that ¹⁸FDG-PET/CT is a more accurate test than either of its components for the evaluation of various tumors. It is a particularly valuable tool for detection of recurrence, especially in asymptomatic patients with rising tumor markers and those with negative or equivocal findings on conventional imaging tests. Yet, there are some limitations and areas of uncertainty, mainly regarding the lack of specificity of the ¹⁸FDG uptake and the variable ¹⁸FDG avidity of some cancers. This article reviews the advantages, limitations and main applications of ¹⁸FDG-PET/CT in oncology, with especial emphasis on lung cancer, colorectal cancer, lymphomas, melanoma and head and neck cancers.

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.