Clinical implication of 18F-FDG PET/CT in carcinoma of unknown primary

Abstract

The value of 18 F-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in the detection of carcinoma of unknown primary (CUP) differs among the studies. This study aimed to evaluate the role of 18 F-FDG PET/CT in CUP.Fifty-one patients (19 women, 32 men) with metastasis confirmed by histopathology from an unknown primary tumor were included in this study. Patients received 370 MBq of 18 F-FDG intravenously, and PET/CT was performed at 60 minutes after injection.Primary tumor sites were detected in 5 of 51 patients (9.6%): in 2 patients with carcinoma of the lung, in 1 patient with carcinoma of the gallbladder, in 1 patient with carcinoma of the esophagus, and in 1 patient with carcinoma of the stomach. No primary tumor was discovered in the remaining 46 patients (90.4%) during the follow-up. The sensitivity, specificity, and accuracy of 18 F-FDG PET/CT were 100%, 80.4%, and 82.4%. The positive and negative predictive values were 35.7 and 100%, respectively.Based on the data presented, 18F-FDG PET/CT has a clinical implicative value in detecting the primary tumor of CUP. PET/CT can be useful to rule out the possibility of detecting the primary tumor during the follow-up.

18F-FDG PET/CT for detection of the primary tumor in adults with extracervical metastases from cancer of unknown primary

“…2), the latter indicating large heterogeneity between studies. The respective Funnel plot was roughly symmetrical, but the 5 studies with the lowest detection rates [20,27,29,30,33] as well as the 2 studies with the highest detection rates [19,28] were outside the funnel, possibly indicating publication bias (Supplemental Digital Content 4). The median FP proportion was 7.5% (range 2.3%–22.2%).…”

“…Available details of diagnostic strategy varied from no registration [19,31,33] to presentation of specific investigations and the number of patients receiving each examination. [26,27,30] Based on studies where diagnostic work-up regimens were presented, many patients underwent a significant array of diagnostic tests, both invasive and noninvasive. This has 2-fold consequences: patients included are highly selected toward the difficult ones since obvious diagnosis will be made in many instances from the standard workup; and the number of unnecessary or futile procedures may be overwhelming to individual patients.…”

“…Only in a few of the studies, the information provided allowed us to determine the separate reference standard on a per-patient basis. [25–27,29,30] In these studies, we accepted the reference standard including clinical follow-up (or other imaging during follow-up) as reference standard to provide an improved standard of comparison.…”

Sensitivity of [18F]FDG PET/CT and classification of the primary tumor site in patients with carcinoma of unknown primary

“…FDG PET/CT should be used as a first-line imaging modality rather than using after other imaging procedures that failed to detect primary tumors [12]. If PET/CT is used as an initial workup, it may reduce the cost, save time and guide the other examinations and biopsies [13]. PET/CT-directed biopsy is also more accurate than random biopsies for the detection of the occult primary tumor [14].…”

Utilidad de la tomografía por emisión de positrones con 18F-fluorodesoxiglucosa-tomografía computarizada en la identificación del tumor primario en pacientes con cáncer de origen desconocido

“…Silva et al 14 refieren que, aunque el rango de detecció n que obtienen con 18 F-FDG PET es de solo un tercio, el alto valor negativo justifica su uso. Por otra parte, existen trabajos de reciente publicació n, como el de Pak et al 15 , que solo detecta por PET-TC el 9,6% de los tumores primarios en una muestra de 51 pacientes.…”