The role of 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography in the management of patients with carcinoma of unknown primary

Role of 18F-FDG PET/CT in Head and Neck Squamous Cell Carcinoma: Current Evidence and Innovative Applications

This article provides an overview of the use of 18F-FDG PET/CT in various clinical scenarios of head-neck squamous cell carcinoma, ranging from initial staging to treatment-response assessment, and post-therapy follow-up, with a focus on the current evidence, debated issues, and innovative applications. Methodological aspects and the most frequent pitfalls in head-neck imaging interpretation are described. In the initial work-up, 18F-FDG PET/CT is recommended in patients with metastatic cervical lymphadenectomy and occult primary tumor; moreover, it is a well-established imaging tool for detecting cervical nodal involvement, distant metastases, and synchronous primary tumors. Various 18F-FDG pre-treatment parameters show prognostic value in terms of disease progression and overall survival. In this scenario, an emerging role is played by radiomics and machine learning. For radiation-treatment planning, 18F-FDG PET/CT provides an accurate delineation of target volumes and treatment adaptation. Due to its high negative predictive value, 18F-FDG PET/CT, performed at least 12 weeks after the completion of chemoradiotherapy, can prevent unnecessary neck dissections. In addition to radiomics and machine learning, emerging applications include PET/MRI, which combines the high soft-tissue contrast of MRI with the metabolic information of PET, and the use of PET radiopharmaceuticals other than 18F-FDG, which can answer specific clinical needs.

2-[18F]FDG-PET/CT in Cancer of Unknown Primary Tumor-A Retrospective Register-Based Cohort Study

We investigated the impact of 2-[18F]FDG-PET/CT on detection rate (DR) of the primary tumor and survival in patients with suspected cancer of unknown primary tumor (CUP), comparing it to the conventional diagnostic imaging method, CT. Patients who received a tentative CUP diagnosis at Odense University Hospital from 2014-2017 were included. Patients receiving a 2-[18F]FDG-PET/CT were assigned to the 2-[18F]FDG-PET/CT group and patients receiving a CT only to the CT group. DR was calculated as the proportion of true positive findings of 2-[18F]FDG-PET/CT and CT scans, separately, using biopsy of the primary tumor, autopsy, or clinical decision as reference standard. Survival analyses included Kaplan-Meier estimates and Cox proportional hazards regression adjusted for age, sex, treatment, and propensity score. We included 193 patients. Of these, 159 were in the 2-[18F]FDG-PET/CT group and 34 were in the CT group. DR was 36.5% in the 2-[18F]FDG-PET/CT group and 17.6% in the CT group, respectively (p = 0.012). Median survival was 7.4 (95% CI 0.4-98.7) months in the 2-[18F]FDG-PET/CT group and 3.8 (95% CI 0.2-98.1) in the CT group. Survival analysis showed a crude hazard ratio of 0.63 (p = 0.024) and an adjusted hazard ratio of 0.68 (p = 0.087) for the 2-[18F]FDG-PET/CT group compared with CT. This study found a significantly higher DR of the primary tumor in suspected CUP patients using 2-[18F]FDG-PET/CT compared with patients receiving only CT, with possible immense clinical importance. No significant difference in survival was found, although a possible tendency towards longer survival in the 2-[18F]FDG-PET/CT group was observed.

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.

Diagnosis and Management of Squamous Cell Carcinoma of Unknown Primary in the Head and Neck: ASCO Guideline

PURPOSE

To provide evidence-based recommendations to practicing physicians and other health care providers on the diagnosis and management of squamous cell carcinoma of unknown primary in the head and neck (SCCUP).

METHODS

The American Society of Clinical Oncology convened an Expert Panel of medical oncology, surgery, radiation oncology, radiology, pathology, and advocacy experts to conduct a literature search, which included systematic reviews, meta-analyses, randomized controlled trials, and prospective and retrospective comparative observational studies published from 2008 through 2019. Outcomes of interest included survival, local and regional disease control, and quality of life. Expert Panel members used available evidence and informal consensus to develop evidence-based guideline recommendations.

RESULTS

The literature search identified 100 relevant studies to inform the evidence base for this guideline. Four main clinical questions were addressed, which included subquestions on preoperative evaluations, surgical diagnostic and therapeutic procedures, appropriate pathology techniques, and adjuvant therapy.

RECOMMENDATIONS

Evidence-based recommendations were developed to address preoperative evaluation for patients with a neck mass, surgical diagnostic and therapeutic procedures, appropriate treatment options in unilateral versus bilateral SCCUP.Additional information is available at www.asco.org/head-neck-cancer-guidelines.

Carcinoma of unknown primary abuts left clavicle: Case report and review of the literature

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Carcinoma of unknown primary clinical manifestations usually associated with head and neck region.

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Painless cervical Lymphadenopathy is the most common symptom of the disease.

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Laboratory tests usually do not identify the primary disease.

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Limited data exists about management and the role of surgery in carcinoma of unknown primary if a single neck mass exists without evidence of lymph node implication.

Introduction

Carcinoma of unknown primary is a well-recognized clinical syndrome which accounts for the 3–5% of all the malignancies. Patients with carcinoma of unknown primary usually present with late stage disease without having identified the primary source of the tumour despite an extensive diagnostic work-up.

Presentation of case

A 60 years old male presented to the clinic complaining of a neck mass to the left lateral neck. Patient’s history was unremarkable without evidence of any malignant disease. Clinical and radiological examination revealed a cystic mass extending from the lower one third of the neck to the left clavicle causing periostal reaction. Mass biopsy and PET-CT was unspecific for the primary origin of the mass. However in the context of tumour immunohistochemistry, HPV status, neck location and basaloid cell differentiation, the tumour mass was considered as carcinoma of unknown primary with possible oropharyngeal primary location. The patient underwent surgical resection of the mass, left clavicle and the first rib. One year after the operation the patient is disease free.

Discussion

Although CUP usually presents with cervical lyphadenopathy, in our case there was no evidence of lymph node tissue infiltration in the neck region. Surgical resection of the mass showed that the location was extending within the cervical soft tissues and upper thorax. Taking into consideration the absence of lymphadenopathy this is an uncommon location of carcinoma of unknown primary in the neck.

Conclusion

This is an uncommon location of CUP with possible implications in survival and management.

18F-FDG PET/CT for detection of the primary tumor in adults with extracervical metastases from cancer of unknown primary: A systematic review and meta-analysis

BACKGROUND

Cancer of unknown primary (CUP) is a heterogeneous group of cancers, so called when a biopsy from a patient reveals malignancy without giving a clue to where in the body the primary tumor is located. Whole-body 18-fluorine-fluorodeoxyglucose positron-emission-tomography/computed tomography (18F-FDG PET/CT) is widely used for diagnosis and staging of most cancers. We hypothesized that 18F-FDG PET/CT-especially if used early-is suitable for the detection of the primary tumor in patients with CUP.

OBJECTIVE

To assess the ability of 18F-FDG PET/CT to detect the primary tumor in adult CUP patients.

DATA SOURCES

PubMed/Medline, Embase, and Web of Science.

STUDY ELIGIBILITY CRITERIA

Studies on CUP from extracervical metastases in which every patient had received an 18F-FDG PET/CT scan and at least one 18F-FDG PET/CT-positive finding was confirmed by biopsy or clinical follow-up.

STUDY APPRAISAL

PRISMA and QUADAS-2 were applied.

SYNTHESIS METHODS

The pooled detection rate (DR) of 18F-FDG PET/CT was assessed with a fixed-effects model. Heterogeneity among studies was assessed with the I-squared statistic.

RESULTS

A total of 2953 articles were identified from which N = 82 were assessed by full text and N = 20, comprising 1942 adult patients, were included in the study. Median (range) number of patients and DR was N = 72 (21-316) and 36.3% (9.8%-75.3%), respectively. Two-thirds of included studies were retrospective, and the pooled DR was 40.93% (95% confidence interval: 38.99%-42.87%). There was large heterogeneity between studies (I-squared = 95.9%), randomization was not applied, CUP diagnosis was not standardized, and workup (if described) was characterized by multiple testing procedures resulting in a highly selected, challenging patient group.

CONCLUSIONS

Despite great heterogeneity in diagnostic workup and in studies in general, an overall DR of 40.93% suggests that upfront application of 18F-FDG PET/CT may have a role in CUP by obviating a great many futile diagnostic procedures. To what degree 18F-FDG PET/CT used early in the course of disease may improve the detection rate could not be deducted from selected articles. A large, prospective, preferably randomized, study on the potential benefit of using 18F-FDG PET/CT up front in CUP patients is warranted to judge if and when 18F-FDG PET/CT should be applied in these patients.

Diagnostic Accuracy of 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography in the Evaluation of Carcinoma of Unknown Primary

Objective:

Detection of primary tumor site in patients with carcinoma of unknown primary (CUP) syndrome has always been a diagnostic dilemma, necessitating extensive workup. Early detection of primary tumor site coupled with specific therapy improves prognosis. The low detection rate of the primary tumor site can be attributed to the biological behavior or the small size of the primary tumor to be detected by conventional imaging. The objective of this study was to evaluate the diagnostic accuracy of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography-computed tomography (PET-CT) in detecting CUP.

Methods:

A retrospective, cross-sectional analysis of 100 PET-CT scans of patients with CUP syndrome between November 2009 and December 2013 was performed. Eighteen patients whose final histopathology results could not be obtained for correlation were excluded from analysis. The hypermetabolic sites were assessed in correlation with histopathology. The diagnostic accuracy, sensitivity, specificity, positive predictive value and negative predictive values were assessed for PET-CT.

Results:

Out of the 82 patients, primary tumor was correctly identified in 57.3% patients by ¹⁸F-FDG PET-CT (true positive). The PET-CT scan results were negative for primary site localization in 15% of patients (false negative). While 21% had true negative results, 7.3% displayed false positive results. PET-CT scan upstaged the disease in 27% cases. Overall, the diagnostic accuracy was found to be 78%, sensitivity 80%, specificity 74%, positive predictive value 88.7% and negative predictive value 59%.

Conclusion:

Our data supports the utility of ¹⁸F-FDG PET-CT scan in the localization and staging of CUP syndrome.