[F-18 FDG PET for detection of occult primary tumor in patients with lymphatic metastases of the neck region]

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.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Les carcinomes de primitif inconnu

PURPOSE

Carcinoma of unknown primary site is a common clinical syndrome, accounting for 2% of cancer patients. Diagnosis is a recurrent challenge for internists. Treatment is difficult and prognosis is still poor. This review presents one synthesis of diagnosis strategies and therapeutic trials. It envisages the interest of new molecular biology methods as well as therapeutic perspectives.

CURRENT KNOWLEDGE AND KEY POINTS

Pathologic examination completed with immunohistochemical tests, and, depending on cases, with electron microscopy, cytogenetics, and molecular biology is a key-point for diagnosis. Diagnosis work-up, based on histological type and on individualization of some clinical presentation, proceeds in three steps. Positron emission tomography is recommended when a curative treatment is planed, particularly in cases of isolated metastasis. Functional status analysed using the performance status and simple biologic parameters (serum lactate dehydrogenase, serum alkaline phosphatase) permit us to assess prognosis. Chemotherapy is offered for patients with a good general health status.

FUTURE PROSPECTS AND PROJECTS

Further evaluation of positron emission tomography, as well as cost-benefit analyses, is warranted. Further randomised trials are necessary to determine the optimal chemotherapy regimen in good-risk patients and the interest of chemotherapy in patients with poor-risk disease. Gene expression profiling and proteomic evaluation, as well as pharmacogenomic offer new investigation fields.

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

BACKGROUND

The authors performed a comprehensive review of the efficacy of fluorodeoxyglucose positron emission tomography (FDG-PET) in the detection of primary tumors in patients with cervical metastases from unknown primary tumors.

METHODS

Sixteen studies (involving a total of 302 patients) published between 1994 and 2003 were reviewed. These studies evaluated the role of FDG-PET in the detection of unknown primary tumors after conventional workup. In all studies, conventional workup included either panendoscopy or computed tomographic/magnetic resonance imaging, and in 10 of 16 studies, both of these diagnostic techniques were performed before diagnosis.

RESULTS

The overall sensitivity, specificity, and accuracy rates of FDG-PET in detecting unknown primary tumors were 88.3%, 74.9%, and 78.8%, respectively. Furthermore, FDG-PET detected 24.5% of tumors that were not apparent after conventional workup. FDG-PET imaging also led to the detection of previously unrecognized metastases in 27.1% of patients (regional, 15.9%; distant, 11.2%). FDG-PET had notably low specificity and a high false-positive rate (39.3%) in the tonsils. In contrast, the false-positive rates for FDG-PET of the base of tongue and hypopharynx were only 21.4% and 8.3%, respectively. FDG-PET exhibited decreased sensitivity to tumors in the base of tongue (81.5%). The sensitivity of this technique at other sites was 90.5%.

CONCLUSIONS

FDG-PET detected primary tumors that went undetected by other modalities in approximately 25% of cases and was sensitive in the detection of previously unrecognized regional or distant metastases in 27% of cases. FDG-PET had low specificity for tonsillar tumors and low sensitivity for base-of-tongue malignancies.

PET: a revolution in medical imaging

FDG-PET has had remarkable influence on the assessment of physiologic and pathologic states. The authors predict that FDG-PET imaging could soon become the most common procedure used by nuclear medicine laboratories and could remain so for an extended period of time. The power of molecular imaging lies in the vast potential for using biochemical and pharmacologic probes to extend applications arising from an understanding of cell biology to a large number of well-characterized pathologic states. Molecular imaging based upon tracer kinetics with positron-emitting radiopharmaceuticals could become the main source of information for the management of cancer patients. In that case, nuclear medicine procedures might become the most common imaging studies performed in the practice of medicine. This speculation is not farfetched when one realizes the enormous change that a single biologically important compound, FDG, has brought to the medical arena. The major challenge today is to attract the highly qualified individuals and to secure the resources needed to harness the opportunities in the specialty of molecular imaging.

Diagnostic strategies for unknown primary cancer

Unknown primary cancer (UPC) is defined by the presence of metastatic disease for which a primary site is undetectable on presentation. Computed tomography scan of the body was performed routinely in search of the primary cancer and invasive procedures were pursued in selective cases. Magnetic resonance imaging of the breast enables identification of an occult breast primary tumor in < or = 75% of women who present with adenocarcinoma in the axillary lymph nodes and can influence surgical management. Positron emission tomography scan also can be used in the diagnosis of UPCs, but its value is controversial. Cytokeratins 7 and 20 and thyroid transcription factor are some of the histochemical markers used in most patients who present with metastatic adenocarcinoma. Some of the newly discovered immunohistochemical markers further assist in narrowing the differential diagnosis. The role of molecular profiling to make the diagnosis, establish the prognosis, and assess the response to treatment in UPCs is evolving. The authors discuss the role of histochemical markers in the diagnosis of UPC and the most recent data regarding the use of imaging and invasive diagnostic modalities and gene expression profiles.

Implications of PET based molecular imaging on the current and future practice of medicine

The last quarter century has witnessed the introduction of a variety of powerful techniques that have allowed visualization of organ structure and function with exquisite detail. This in turn has brought about a true revolution in the day-to-day practice of medicine. Structural imaging with x-ray computerized tomography and magnetic resonance imaging has added tremendously to many areas of medicine, including preoperative evaluation of patients. Many surgical procedures have been replaced by minimally invasive techniques, which have become a reality only because of the availability of modern imaging modalities. However, despite such accomplishments, structural imaging is quite insensitive for detecting early disease in which there often are no gross structural alterations in organ anatomy. Therefore, these modalities should be complemented by methodologies that can detect abnormalities at the molecular and cellular levels. The introduction of [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET) in 1976 as a molecular imaging technique clearly has shown the power of this approach for treating a multitude of serious disorders. The impact of FDG-PET has been particularly impressive in patients with cancer diagnosis, for whom it has become important in staging, monitoring response to treatment, and detecting recurrence. In this review, we emphasize the role of FDG-PET in the assessment of central nervous system maladies, malignant neoplastic processes, infectious and inflammatory diseases, and cardiovascular disorders. New radiotracers are being developed and promise to expand further the list of indications for PET. These include novel tracers for cancer diagnosis and treatment capable of detecting hypoxia and angiogenesis. Prospects for developing new tracers for imaging other organ diseases also appear very promising.

The Impact of FDG PET on the Management of Occult Primary Head and Neck Tumours

AIMS

The aim of this study was to investigate the impact of positron-emission tomography (PET) with 18F-labelled fluoro-2-deoxy-D-glucose (FDG) in the management of occult primary head and neck tumours.

MATERIALS AND METHODS

We reviewed 16 patients with squamous cell carcinoma (SCC) and one patient with undifferentiated carcinoma of cervical lymph nodes (N1-4; N2a-9; N2b-2; N3-2). All patients had full clinical assessment, including examination under anaesthesia (EUA), with biopsy of all suspicious areas and random biopsies of sites likely to harbour an occult primary site. Nine patients underwent magnetic resonance imaging (MRI) of the head and neck, three underwent computed tomography (CT) and five underwent both CT and MRI. None of these studies were able to locate a primary tumour. Patients received 350 MBq FDG intravenously. Emission transmission scans of the extra-cranial head, neck and thorax were obtained using an ECAT Exact 47 at least 60 min after injection. The images were interpreted by the same radiologist experienced in PET, independent of the final outcome. The influence of FDG PET on management was assessed on review of the patients' notes after treatment or when treatment had been deemed unnecessary.

RESULTS

FDG PET suggested a primary site in eight of the 17 patients (tongue base 5; nasopharynx 1; tonsil 1: supraglottis 1). Pathological confirmation was obtained in four patients and one patient died of progressive disease at the primary site. In nine patients, the primary site was not identified on FDG PET. In six of these patients, no primary site was found during follow-up (range 8-36 months: mean 20 months). One patient died before treatment commenced, and there were two histologically confirmed false-negative FDG PET results: one tonsil SCC and one lateral pharyngeal wall SCC. FDG PET affected treatment plans in nine of the 17 (53%) patients in whom a primary site was suggested (altered radiotherapy plan 6; radiotherapy with curative intent to palliative radiotherapy 1; radiotherapy to surgery and post-operative radiotherapy 1), and in one patient where no occult primary was localised (radiotherapy to surgery 1). FDG PET had a sensitivity, specificity, positive and negative predictive value of 62%, 66%, 62% and 62%, respectively.

Lymph node metastasis of squamous cell carcinoma from an unknown primary: impact of positron emission tomography

This study was performed to assess the potential benefit of positron emission tomography (PET) using fluorine-18 fluorodeoxyglucose (FDG) in patients with cervical metastasis of squamous cell carcinoma from an unknown primary tumour. Eighteen patients with cervical metastasis of squamous cell carcinoma from an unknown primary who were assessed by physical examination including transnasal fibre-endoscopy and radiological work-up with computed tomography were included in this prospective tertiary referral centre cohort study. The results of the search for the primary with rigid panendoscopy of the upper aerodigestive tract were compared to the evaluation with FDG PET. Panendoscopy revealed a primary tumour in 8/18 (44%) patients. PET accurately diagnosed five of these eight primary tumours, and gave one false positive and three false negative scans, resulting in a sensitivity of 63%, a specificity of 90%, an accuracy of 78%, a positive predictive value of 83% and a negative predictive value of 75%. Small primaries or primaries in areas with physiologically increased FDG uptake can be missed with PET owing to the limited resolution of the camera (approximately 5 mm). Our study in a small number of patients suggests that PET does not provide benefit in terms of detecting additional primary tumours if applied in addition to extensive clinical work-up. Considering its high specificity, PET could be of value as an initial evaluation instrument, reserving the need for extensive work-up to patients with negative scans.

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

BACKGROUND

The usefulness of fluorine 18-labelled deoxyglucose positron emission tomography (PET) in the detection of unknown primary tumor in patients seen with malignant cervical lymphadenopathy thought to arise from a head and neck primary differs in the published reports to date. To assess the role of PET in this scenario in our institution, an audit was performed.

METHODS

The records of 21 patients who met the clinical indication were reviewed. End points were the ability of PET to detect an unknown primary tumor and/or distant metastatic disease.

RESULTS

In 8 of the 21 patients, PET detected a potential primary site, although none was unequivocally PET positive. One case was pathologically confirmed. In five patients the potential primary site identified on PET could not be confirmed: two had negative biopsies, and three had no clinical evolution in the PET-suspect area for at least 24 months after the initial study. In the remaining two patients, the potential primary site detected by PET was treated without biopsy. PET detected additional regional and/or distant disease that had not been previously documented in nine cases.

CONCLUSIONS

PET did not add significantly to the detection of an occult primary tumor in patients who had already been comprehensively evaluated by clinical and radiologic investigations. It was of substantial benefit, however, in detecting unsuspected distant disease in patients with undifferentiated nodal histologic findings and helped in delineating regional disease in patients with N2 disease.

Cervical lymph node metastases from occult squamous cell carcinoma: cut down a tree to get an apple?

PURPOSE

To review the value of extended diagnostic work-up procedures and to compare the results of comprehensive or volume-restricted radiotherapy in patients presenting with cervical lymph node metastases from clinically undetectable squamous cell carcinoma.

METHODS AND MATERIALS

A systematic review was undertaken of published papers up to May 2000.

RESULTS

Positron emission tomography (PET) has an overall staging accuracy of 69%, with a positive predictive value of 56% and negative predictive value of 86%. With negative routine clinical examination and computerized tomography (CT) or magnetic resonance imaging (MRI), PET detected primary tumors in 5-25% of patients, whereas ipsilateral tonsillectomy discovered carcinoma in about 25% of patients. Laser-induced fluorescence imaging with panendoscopy and directed biopsies showed some encouraging preliminary results and warrants further study. All together, the reported mucosal carcinoma emergence rates were 2-13% (median, 9.5%) after comprehensive radiotherapy and 5-44% (median, 8%) after unilateral neck irradiation. The corresponding nodal relapse rates were 8-45% (median, 19%) and 31-63% (median, 51.5%), and 5-year survival rates were 34-63% (median, 50%) and 22-41% (median, 36.5%), respectively. Retrospective single-institution comparisons between comprehensive and unilateral neck radiotherapy did not show apparent differences in outcome. Prognostic determinants for survival are the N stage, number of nodes, extracapsular extension, and histologic grade. No data were found to support the benefit of chemotherapy in this disease.

CONCLUSION

Physical examination, CT or MRI, and panendoscopy with biopsies remain the standard work-up for these patients. Routine use of PET or laser-induced fluorescence imaging cannot be firmly advocated based on presently available data. Although combination of nodal dissection with comprehensive radiotherapy yielded most favorable results, its impact on the quality of life should be recognized, and the confounding effects of patient selection for various treatment modalities on therapeutic outcome cannot be ruled out. A randomized trial comparing the therapeutic value of comprehensive vs. volume-limited radiotherapy is being considered.