Unknown primary tumors: detection with dual-modality PET/CT--initial experience

Identifying the primary tumour in patients with cancer of unknown primary (CUP) using [18F]FDG PET/CT: a systematic review and individual patient data meta-analysis

PURPOSE

In this systematic review and individual patient data (IPD) meta-analysis, we analysed the diagnostic performance of [18F]FDG PET/CT in detecting primary tumours in patients with CUP and evaluated whether the location of the predominant metastatic site influences the diagnostic performance.

METHODS

A systematic literature search from January 2005 to February 2024 was performed to identify articles describing the diagnostic performance of [18F]FDG PET/CT for primary tumour detection in CUP. Individual patient data retrieved from original articles or obtained from corresponding authors were grouped by the predominant metastatic site. The diagnostic performance of [18F]FDG PET/CT in detecting the underlying primary tumour was compared between predominant metastatic sites.

RESULTS

A total of 1865 patients from 32 studies were included. The largest subgroup included patients with predominant bone metastases (n = 622), followed by liver (n = 369), lymph node (n = 358), brain (n = 316), peritoneal (n = 70), lung (n = 67), and soft tissue (n = 23) metastases, leaving a small group of other/undefined metastases (n = 40). [18F]FDG PET/CT resulted in pooled detection rates to identify the primary tumour of 0.74 (for patients with predominant brain metastases), 0.54 (liver-predominant), 0.49 (bone-predominant), 0.46 (lung-predominant), 0.38 (peritoneal-predominant), 0.37 (lymph node-predominant), and 0.35 (soft-tissue-predominant).

CONCLUSION

This individual patient data meta-analysis suggests that the ability of [18F]FDG PET/CT to identify the primary tumour in CUP depends on the distribution of metastatic sites. This finding emphasises the need for more tailored diagnostic approaches in different patient populations. In addition, alternative diagnostic tools, such as new PET tracers or whole-body (PET/)MRI, should be investigated.

Contribution of FDG-PET in the diagnostic assessment of cervical lymph node metastasis in Oral Cavity Squamous Cell Carcinoma (OCSCC)

INTRODUCTION

The main objective of this study was to evaluate the contribution of FDG-PET in the diagnostic assessment of cervical lymph node metastasis in Oral Cavity Squamous Cell Carcinoma (OCSCC) and to advance a diagnostic threshold value for SUVmax in carcinomatous cervical lymph node.

METHODS

47 patients with OCSCC and suspicious cervical lymph node involvement (cN+) on FDG-PET were included in this retrospective study. The primary outcome was cervical lymph node SUVmax based on histological cervical metastatic disease (« gold standard »).

RESULTS

Among the 77 cervical lymph nodes considered suspicious on patients' FDG-PET, 50 were really metastatic on histological examination. The lymph node SUVmax with metastatic involvement on histological examination was 4.6 ± 3.9 [2.6 - 23.7] versus 3.6 ± 1.2 [2 - 7.3] without carcinomatous involvement (p = 0.004). The lymph node size was not statistically significant according to metastatic disease (p = 0.28).

DISCUSSION

A cervical lymph node SUVmax value of less than 2.6 on FDG-PET would suggest non-metastatic lymph node involvement. Supra Omohyoid Neck Dissection (SOHND) could therefore be performed in OCSCC when the SUVmax of the cervical lymph node is below this value in order to reduce the surgical morbidity of dissection of the lower internal jugular chain (Level IV).

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.

Utility of RNA Expression to Determine the Tissue of Origin of Malignancies with an Inconclusive Histopathology

We present 2 cases of cancer of unknown origin in which RNA-based cancer classification testing provided vital insight and directed treatment management. The tissue of origin could not be determined in both of these patients utilizing morphology and immunohistochemical analysis of the tissue samples. Next-generation sequencing and tumor-of-origin testing using an RNA-based molecular cancer classifier were performed to elucidate the possible tissue of origin. A 61-year-old male with a history of localized basal cell carcinoma presented with a 4.4-cm axillary lymph node in addition to upper extremity edema and supraclavicular lymphadenopathy. RNA-based tumor origin testing revealed skin basal or squamous cell carcinoma as the likely tissue of origin, with a probability of 97%. He received vismodegib, a hedgehog inhibitor, after progression on cemiplimab and experienced a partial response by RECIST criteria, which is currently ongoing for over a year. A 74-year-old female patient with a remote history of ovarian cancer for which she underwent resection and adjuvant chemotherapy presented 15 years later with abdominal pain. The diagnostic workup revealed a 2-cm pancreatic mass and enlarged peritoneal lymph nodes. RNA sequencing revealed a 99% likelihood of the tissue of origin being serous ovarian carcinoma. Subsequently, she underwent surgery and adjuvant chemotherapy and is currently in remission with letrozole maintenance. Genomic data already plays a crucial role in therapeutic decision-making for individuals with cancer. These cases highlight the complementary role of genomic data in the diagnostic workup of cancer, leading to favorable patient outcomes.

An accurate prediction of the origin for bone metastatic cancer using deep learning on digital pathological images

BACKGROUND

Determining the origin of bone metastatic cancer (OBMC) is of great significance to clinical therapeutics. It is challenging for pathologists to determine the OBMC with limited clinical information and bone biopsy.

METHODS

We designed a regional multiple-instance learning algorithm to predict the OBMC based on hematoxylin-eosin (H&E) staining slides alone. We collected 1041 cases from eight different hospitals and labeled 26,431 regions of interest to train the model. The performance of the model was assessed by ten-fold cross validation and external validation. Under the guidance of top3 predictions, we conducted an IHC test on 175 cases of unknown origins to compare the consistency of the results predicted by the model and indicated by the IHC markers. We also applied the model to identify whether there was tumor or not in a region, as well as distinguishing squamous cell carcinoma, adenocarcinoma, and neuroendocrine tumor.

FINDINGS

In the within-cohort, our model achieved a top1-accuracy of 91.35% and a top3-accuracy of 97.75%. In the external cohort, our model displayed a good generalizability with a top3-accuracy of 97.44%. The top1 consistency between the results of the model and the immunohistochemistry markers was 83.90% and the top3 consistency was 94.33%. The model obtained an accuracy of 98.98% to identify whether there was tumor or not and an accuracy of 93.85% to differentiate three types of cancers.

INTERPRETATION

Our model demonstrated good performance to predict the OBMC from routine histology and had great potential for assisting pathologists with determining the OBMC accurately.

FUNDING

National Science Foundation of China (61875102 and 61975089), Natural Science Foundation of Guangdong province (2021A15-15012379 and 2022A1515 012550), Science and Technology Research Program of Shenzhen City (JCYJ20200109110606054 and WDZC20200821141349001), and Tsinghua University Spring Breeze Fund (2020Z99CFZ023).

Real-Life Performance of F-18-FDG PET/CT in Patients with Cervical Lymph Node Metastasis of Unknown Primary Tumor

Background: Neoplasms in the head and neck region possess higher glycolytic activity than normal tissue, showing increased glucose metabolism. F-18-Flourodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) can identify an unknown primary tumor (CUP). Aim: The aim of this study was to assess the real-life performance of F-18-FDG-PET/CT in detecting primary sites in patients with cervical lymph node metastasis of CUP. Methods: A retrospective data analysis of 31 patients who received FDG-PET/CT between June 2009 and March 2015 in a CUP context with histologically confirmed cervical lymph node metastasis was included. Results: In 48% of the patients (15/31), PET/CT showed suspicious tracer accumulation. In 52% of the patients (16/31), there was no suspicious radiotracer uptake, which was confirmed by the lack of identification of any primary tumor in 10 cases until the end of follow-up. FDG-PET/CT had a sensitivity of 67%, specificity of 91%, PPV of 92%, and NPV of 63% in detecting the primary tumor. Additionally, PET/CT showed suspicious tracer accumulation according to further metastasis in 32% of the patients (10/31). Conclusion: FDG-PET/CT imaging is a useful technique for primary tumor detection in patients in a cervical CUP context. Furthermore, it provides information on the ulterior metastasis of the disease.

Diagnostic efficiency of PET/CT in patients with cancer of unknown primary with brain metastasis as initial manifestation and its impact on overall survival

Background

Carcinoma of unknown primary (CUP) is a diagnostic and therapeutic challenge; correct diagnostic approach results in better outcomes in patients with brain metastasis. Whole body 18 F-FDG PET/CT is a helpful modality to detect the origin of primary tumor and assess metastasis in the rest of the body. We assessed the value of PET/CT in detection of unknown primary in 39 patients with brain metastases as initial presentation and detected its impact on their overall survival.

Results

PET/CT could correctly detected the primary tumor in 49% of patients which occurred mainly in the lung, 63% of patients had additional extracerebral metastatic sites mostly in lymph nodes. Specificity, sensitivity, and accuracy of PET/CT in CUP patients were 95%, 79%, and 87%, respectively. No significant difference was noticed in estimated overall survival time between patients with an identified primary tumor and patients with unidentified primary tumor.

Conclusion

PET–CT was a helpful non-invasive imaging modality in detecting primary in CUP patients with metastatic brain lesion. It helped in the diagnosis of unexpected extracerebral metastatic lesions. However, the identification of the primary tumor by PET/CT has no significant prognostic effect on patient overall survival.

A Case Report of Squamous Cell Carcinoma of Unknown Primary That Metastasized to an Inguinal Lymph Node

The term carcinoma of unknown primary (CUP) refers to a malignant tumor whose histology suggests strongly that it is a metastasis, yet the primary lesion is unknown despite sufficient whole body evaluation at the time of examination. CUP has similar incidences in men and women and the average age at diagnosis is 60 years. While its overall incidence varies depending on the report, it generally accounts for 1-5% of all cancers. Thus, it is rare. We encountered a case of squamous cell carcinoma of the inguinal region that seemed to be a metastasis and for which we could not find the primary lesion. This case is reported here along with a literature review on CUP to increase awareness of this rare lesion.

Pivotal role of PET/CT in characterization of occult metastasis with undetermined origin

Background

The purpose of this multicenter diagnostic accuracy test study was conducted to assess the role of positron emission tomography/computed tomography in the detection of primary tumor in cases of metastasis of undetermined primary site, to estimate its capability in detecting additional lesions as well as evaluating disease burden and staging. This multicentric diagnostic accuracy test study included 175 patients with pathologically proven, radiologically, and/or clinically suspected metastatic lesions of undetermined primary site. Clinical, surgical, and histopathologic findings and correlative imaging modalities were used to assess the results of PET/CT; the accuracy of PET/CT was expressed in terms of sensitivity and specificity, positive and negative predictive values.

Results

The study included 175 patients; PET-CT-positive lesions suggestive of primary malignant tumors were detected in 105 out of 175 patients. These lesions were pathologically proven to be malignant (true positive) in 100/175 patients (57.1%). Five out of 175 patients (2.9%) proved to be falsely positive after pathologic assessment; 70 out of 175 patients (40%) were negative for detection of primary malignancy all over the body by PET/CT (true negative) with no false negative results. PET/CT achieved a sensitivity of 100%, and specificity of 93.3% in detection of unknown primary tumor location.

Conclusion

PET/CT is an effective modality for early detection of the primary tumor site in patients with cancer of undetermined primary (CUP) which facilitates early selection of appropriate treatment protocols that will improve patients’ prognosis.

Pancreatic adenocarcinoma with early esophageal metastasis: A case report and review of literature

BACKGROUND

Pancreatic adenocarcinoma is an aggressive malignancy with a high propensity to metastasize. Esophageal metastasis manifesting as dysphagia is rarely reported in the literature and has not to our knowledge been reported prior to the appearance of the primary disease.

CASE SUMMARY

A patient presented with progressive dysphagia to solids and a persistent earache. Computed tomography of the neck and chest revealed a 3.0 cm × 1.8 cm heterogeneous mass originating from the upper third of the esophagus, necrotic cervical and supraclavicular lymphadenopathy, and bilateral pulmonary nodules. She underwent a core needle biopsy of a right cervical node, which suggested a well-differentiated adenocarcinoma of unknown primary. She had an upper endoscopy with biopsy of the esophageal mass suggestive of a well-differentiated adenocarcinoma. Positron emission tomography imaging revealed increased uptake in the esophageal mass, cervical, and mediastinal lymph nodes. She was started on folinic acid, fluorouracil, and oxaliplatin. Prior to initiation of cycle 8, the patient was found to have a pancreatic body mass that was not present on prior radiographic imaging, confirmed by endoscopic ultrasonography and biopsy to be pancreatic adenocarcinoma. CA19-9 was > 10000 U/mL, suggesting a primary pancreaticobiliary origin.

CONCLUSION

Esophageal metastasis diagnosed before primary pancreatic adenocarcinoma is rare. This case highlights the profound metastatic potential of pancreatic adenocarcinoma.

Head and neck carcinoma of unknown primary

In adult cervicofacial pathology, carcinoma of unknown primary is defined as lymph-node metastasis the anatomic origin of which is not known at the time of initial management. It constitutes up to 5% of head and neck cancers. Presentation may suggest benign pathology, delaying and confusing oncologic treatment. Diagnostic strategy in cervical lymph node with suspicion of neoplasia requires exhaustive work-up to diagnose malignancy and, in 45% to 80% of cases, depending on the series, to identify the primary site. Histologic types comprise squamous cell carcinoma, thyroid carcinoma, adenocarcinoma, neuroendocrine carcinoma and undifferentiated carcinoma. Association is sometimes found with human papilloma virus or Epstein Barr virus, guiding treatment. The objective of the present study was to provide clinicians with the necessary diagnostic tools, based on the current state of clinical, imaging and pathologic knowledge, and to detail treatment options.

Diagnostic Value of 18F-FDG PET/CT in Patients with Carcinoma of Unknown Primary

Objective:

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

Methods:

One hundred twenty one patients with a diagnosis of CUP who underwent whole body ¹⁸F-FDG PET/CT imaging were included in this retrospective study. The final diagnoses were confirmed either histopathologically or by clinical follow-up.

Results:

The ¹⁸F-FDG-PET/CT successfully detected the primary tumor in 59 out of 121 (49%) patients. The most common primary tumor as detected by ¹⁸F-FDG PET/CT was lung cancer (n=31). In a patient, two primary tumors (colon and prostate) were detected on PET/CT imaging. Bone marrow biopsy revealed prostate cancer in this patient and the colon cancer was accepted as a synchronous second primary tumor. ¹⁸F-FDG PET/CT findings were false-positive in 11 patients. ¹⁸F-FDG PET/CT could not detect any primary lesion in 51 patients, whose conventional work-up detected a primary tumor in 11 and thus considered as false-negative. The sensitivity, specificity rate and accuracy of ¹⁸F-FDG PET/CT in detection of primary tumor were identified as 84%, 78% and 82%, respectively.

Conclusion:

Whole body ¹⁸F-FDG PET/CT is an effective method for detecting the primary tumor in patients with CUP. In addition to detecting the primary tumor, it can also help determine disease extent and contribute to patient management.

FDG PET/CT and Conventional Imaging Methods in Cancer of Unknown Primary: an Approach to Overscanning

Purpose

To compare the performance of fluorine-18 fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) with conventional imaging methods (CIM), including computed tomography (CT), magnetic resonance imaging (MRI), and mammography (MMG) in cancer of unknown primary (CUP).

Methods

A total of 36 patients with CUP, who referred to our clinic for a FDG PET/CT scan, were enrolled in this study. Thirty of the patients were also examined through either diagnostic CT/MRI and/or MMG. The diagnostic performance of both methods for the primary cancer location was analyzed. The results of FDG PET/CT and CIM were compared based on the standard reference of the histopathology and/or clinical and laboratory follow-up.

Results

The primary cancer locations were detected in 24 patients (66.6%, 24/36) by FDG PET/CT, whereas CIM identified the locations in 16 patients (53.3%, 16/30). Sensitivity, specificity, PPV, NPV, and accuracy rates of the detection of the primary tumor localizations were as follows: 83, 70, 89, 58, and 79% for FDG PET/CT; 70, 62, 84, 42, and 68% for CIM, respectively. There was no statistical significance between modalities regarding any of the categories in 30 patients.

Conclusion

FDG PET/CT detected the primary tumors of the patients with CUP more than CIM did. However, the difference between them was not found to be statistically significant. It may be considered that FDG PET/CT scan can be performed as a first-line tool in the initial diagnosis of the patients with CUP and to add radiodiagnostic imaging in selective cases. We conclude that if the first-line examination of a CUP patient has been already performed by a CIM and the result was negative or inconclusive, FDG PET/CT can be considered to avoid unnecessary imaging procedures.

Efficacy of 18F-fluorodeoxyglucose PET/CT for Detecting Lymph Node Metastasis in Papillary Thyroid Carcinoma

Objective

To evaluate the efficacy of preoperative ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) for detecting cervical lymph node (LN) metastasis in papillary thyroid carcinoma (PTC).

Study Design

Case series with chart review.

Setting

University tertiary care facility.

Subjects and Methods

We retrospectively compared the pathologic results for 409 cervical LN levels in 140 patients who underwent thyroidectomy and central neck dissection with/without lateral neck dissection with the findings of preoperative PET/CT, ultrasonography (US), and CT. We judged LN metastasis in PET/CT using the maximum standardized uptake value (SUVmax) at the optimal cutoff value in receiver operating characteristic curves and compared the sensitivity, specificity, and diagnostic accuracy of the 3 imaging tools.

Results

At all neck levels (central and lateral compartments), PET/CT had a sensitivity of 57.5%, specificity of 68.6%, and diagnostic accuracy of 63.6% when the cutoff value of SUVmax was 1.125. The corresponding values were 59.1%, 90.6%, and 76.3%, respectively, for US and 53.8%, 91.9%, and 74.6% for CT. In the central compartment (level VI), sensitivity, specificity, and diagnostic accuracy were 48.9%, 67.4%, and 59.9% for PET/CT (cutoff SUVmax 1.125); 47.8%, 96.3%, and 76.7% for US; and 41.3%, 97.0%, and 74.4% for CT, respectively. In the lateral compartment (levels II-V), the corresponding values of sensitivity, specificity, and diagnostic accuracy were 70.2%, 69.3%, and 69.8% for PET/CT (cutoff SUVmax 1.055); 70.2%, 81.8%, and 75.8% for US; and 65.9%, 84.1%, and 74.7% for CT.

Conclusion

PET/CT is less effective as a preoperative diagnostic tool for detecting cervical lymph node metastasis in PTC than US or CT.

Precision medicine based on epigenomics: the paradigm of carcinoma of unknown primary

Epigenetic alterations are a common hallmark of human cancer. Single epigenetic markers are starting to be incorporated into clinical practice; however, the translational use of these biomarkers has not been validated at the 'omics' level. The identification of the tissue of origin in patients with cancer of unknown primary (CUP) is an example of how epigenomics can be incorporated in clinical settings, addressing an unmet need in the diagnostic and clinical management of these patients. Despite the great diagnostic advances made in the past decade, the use of traditional diagnostic procedures only enables the tissue of origin to be determined in ∼30% of patients with CUP. Thus, development of molecularly guided diagnostic strategies has emerged to complement traditional procedures, thereby improving the clinical management of patients with CUP. In this Review, we present the latest data on strategies using epigenetics and other molecular biomarkers to guide therapeutic decisions involving patients with CUP, and we highlight areas warranting further research to engage the medical community in this unmet need.

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.

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.

Impact on Patient Management of [18F]-Fluorodeoxyglucose-Positron Emission Tomography (PET) Used for Cancer Diagnosis: Analysis of Data From the National Oncologic PET Registry

INTRODUCTION

We assessed the impact of [(18)F]-fluorodeoxyglucose (FDG)-positron emission tomography (PET) on intended management of patients in the National Oncologic PET Registry (NOPR) for three different diagnostic indications: (a) determining whether a suspicious lesion is cancer (Dx), (b) detecting an unknown primary tumor site when there is confirmed or strongly suspected metastatic disease (cancer of unknown primary origin [CUP]), and (c) detecting a primary tumor site when there is a presumed paraneoplastic syndrome (PNS).

METHODS

We reviewed a sample of randomly selected reports of NOPR subjects who underwent PET for Dx and CUP and all reports for PNS to find subjects for analysis. For these studies, we evaluated the impact of PET on referring physicians' intended management, based on their management plans reported before and after PET.

RESULTS

Intended management was changed more frequently in the CUP group (43.1%) than in the Dx (23.9%) and PNS (25.4%) groups (CUP vs. Dx, p < .0001; PNS vs. Dx, p < .0001; CUP vs. PNS, p < .0002). Referring physicians reported that, in light of PET results, they were able to avoid further testing in approximately three-fourths of patients (71.8%-74.6%). At the time when the post-PET forms were completed, biopsies of suspicious sites had been performed in 21.2%, 32.4%, and 23.2%, respectively, of Dx, CUP, and PNS cases.

CONCLUSION

Our analysis of NOPR data shows that PET appears to have a substantial impact on intended management when used for three common diagnostic indications.

IMPLICATIONS FOR PRACTICE

[(18)F]-fluorodeoxyglucose-positron emission tomography appears to have a substantial impact on intended management when used for three targeted diagnostic indications: (a) determining whether a suspicious lesion is cancer, (b) detecting an unknown primary tumor site in a patient with confirmed or strongly suspected metastatic disease, and (c) detecting a primary tumor site in a patient with a presumed paraneoplastic syndrome.

Carcinoma of unknown primary in the head and neck: The evaluation of the effectiveness of (18)F-FDG-PET/CT, own experience

AIM

The aim of the present study was to estimate the clinical effectiveness of (18)F-FDG-PET/CT in the detection of the primary tumor in patients with histologically proven squamous cell carcinoma cervical lymph nodes metastasis from an unknown primary.

BACKGROUND

(18)F-fluorodeoxyglucose positron emission tomography combined with CT ((18)F-FDG-PET/CT) is believed to be very helpful in localization of primary tumor in CUP Syndrome patients.

MATERIAL AND METHOD

41 patients referred to Poznan Medical University Department of Head and Neck Surgery from January 2010 to December 2013 with CUP Syndrome were included in the study. All patients presented fine-needle biopsy proven squamous cell carcinoma metastasis of the upper-, or mid neck lymph nodes. The final results were obtained from the histopathologic reports of tissue samples from anatomical regions suspected for primary tumor, additional imaging exams as well as clinical follow-up data.

RESULTS

The (18)F-FDG-PET/CT successfully detected primary tumor in 7 out of 41 patients (17%). In two more cases the primary tumor was indicated in the lung. 24 of 41 patients (58.5%) analyzed in our study remained without evidence of a primary tumor. In 4 cases (9.75%) we did not reveal any pathology within the localizations indicated by PET/CT on panendoscopy. In 4 cases we obtained histological confirmation of neoplasm on panendoscopy despite the negative results of PET/CT examinations.

CONCLUSION

We may suppose a relatively high usefulness of (18)F-FDG-PET/CT in the diagnosis process of CUP Syndrome patients. High NPV may indicate patients with no symptoms of primary tumor, which allows to avoid extensive resection or extra imaging.

Contrast-enhanced [18F] fluorodeoxyglucose-positron emission tomography-computed tomography as an initial imaging modality in patients presenting with metastatic malignancy of undefined primary origin

Background:

To evaluate the advantages of contrast enhanced F-18-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-contrast enhanced CT [CECT]) when used as an initial imaging modality in patients presenting with metastatic malignancy of undefined primary origin (MUO).

Materials and Methods:

A total of 243 patients with fine needle aspiration cytology/biopsy proven MUO were included in this prospective study. Patients who were thoroughly evaluated for primary or primary tumor was detected by any other investigation were excluded from the analysis. Totally, 163 patients with pathological diagnosis of malignancy but no apparent sites of the primary tumor were finally selected for analysis. The site of probable primary malignancy suggested by PET-CECT was confirmed by biopsy/follow-up.

Results:

PET-CECT suggested probable site of primary in 128/163 (78.52%) patients. In 30/35 remaining patients, primary tumor was not detected even after extensive work-up. In 5 patients, where PET-CECT was negative, primary was found on further extensive investigations or follow-up. The sensitivity, specificity, positive predictive value and negative predictive value of the study were 95.76%, 66.67%, 88.28% and 85.71% respectively.

Conclusions:

F-18 FDG PET-CECT aptly serves the purpose of initial imaging modality owing to high sensitivity, negative and positive predictive value. PET-CECT not only surveys the whole body for the primary malignancy but also stages the disease accurately. Use of contrast improves the diagnostic utility of modality as well as help in staging of the primary tumor. Although benefits of using PET-CECT as initial diagnostic modality are obvious from this study, there is a need for a larger study comparing conventional methods for diagnosing primary in patients with MUO versus PET-CECT.

Impact of (18)f-fluorodeoxyglucose positron emission tomography/computed tomography scan on initial evaluation of head and neck squamous cell carcinoma: our experience at a tertiary care center in India

The efficacy of the whole body (WB) ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography-computed tomography (PET-CT) as a part of conventional initial staging in all cases of head and neck squamous cell carcinoma (HNSCC) is still controversial with various studies in literature giving contradictory reports. We conducted this study at a government tertiary care oncology center in India to identify the impact of WB ¹⁸F-FDG PET-CT scan on HNSCC staging and treatment. A prospective clinical study of patients of HNSCC who were evaluated and treated at our center was performed. The patients included in the study were HNSCC of the oral cavity, oropharynx, hypopharynx, larynx, nasopharynx, and carcinoma of unknown primary site (CUPS) with cervical metastasis. The study design was to evaluate the cases of HNSCC initially by staging with conventional investigations followed by staging with the information derived from WB ¹⁸F-FDG PET-CT scan. At the end of the conventional investigations, a tumor, node, metastasis (TNM) staging as per AJCC 7^th edition, and a detailed treatment plan as per NCCN 2012 guidelines was decided in consultation with the multidisciplinary oncology team of the hospital. WB ¹⁸F-FDG PET-CT scan was carried out in all these patients. The findings of WB ¹⁸F-FDG PET-CT were then interpreted with the staging with conventional investigations to identify the cases with change in staging and also those in whom the treatment protocol would be affected. Descriptive analysis of demographic data and analytical analysis of the sensitivity and specificity of WB ¹⁸F-FDG PET-CT scan and also the change in staging and treatment plan after WB ¹⁸F-FDG PET-CT scan was analyzed using SPSS version 18. A total of 131 patients met the inclusion criteria, which included 123 males and 8 females. The various sites involved among the study group are oral cavity 11 (8.3%), oropharyn × 39 (29.7%), hypopharyn × 31 (23.6%), laryn × 34 (25.9%), nasopharyn × 4 (3%), and CUPS 12 (9.1%). The majority of cases studied were of T2 and T3 stage, and changes in T staging after WB ¹⁸F-FDG PET-CT scan were minimal and not statistically significant (P > 0.5). In the nodal staging after WB ¹⁸F-FDG PET-CT scan, there was a statistically significant change in identification of nodal metastasis in N0 group and also identification of additional multiple/bilateral nodes (N2b and N2c). 3 (2.2%) patients had a change in M status with identification of distant metastasis in lungs (2 patients) and in the liver and lung (1 patient). Of the 131 patients, 75 (57.25%) underwent surgical management with or without adjuvant treatment (Group I) and 56 (42.74%) patients underwent nonsurgical management (Group II). There was no significant statistical difference in sensitivity and specificity of ¹⁸F-FDG PET-CT scan in detecting cancer among the two groups. Considering all the patients in this study, WB ¹⁸F-FDG PET-CT scan showed an overall sensitivity of 95.2% and specificity of 80%. In this study, change in TNM staging after WB ¹⁸F-FDG PET-CT was seen in 22 (16.8%) patients and an alteration in the treatment in 21 (16.1%) patients, which were both found to be statistically significant (P < 0.5). In our study, WB ¹⁸F-FDG PET-CT scan has shown to have an impact on initial staging of disease affecting the change in treatment protocol in a significant number of patients. The effect of this change in staging and treatment on the eventual morbidity and mortality rates is not known. In practice, the use of ¹⁸F-FDG PET-CT scan is limited, owing to the high cost and low availability. A realistic evaluation of cost versus benefit needs to be undertaken to identify the impact of using ¹⁸F-FDG PET-CT scan as a mode for initial evaluation of HNSCC.

[Importance of nuclear medicine diagnostics in CUP syndrome]

CLINICAL/METHODICAL ISSUE

The diagnostic work-up in patients with carcinoma of unknown primary (CUP) syndrome is extensive, highly time-consuming and cost-intensive and ultimately often fails to detect a primary site.

STANDARD RADIOLOGICAL METHODS

In this context chest X-ray and computed tomography (CT) have been used as standard imaging modalities in CUP syndrome.

METHODOLOGICAL INNOVATIONS

Since the introduction of positron emission tomography (PET) evaluation of tumor vitality has become possible. Furthermore, PET-CT hybrid scanners allow the combination of functional and morphological imaging.

PERFORMANCE

Several meta-analyses have reported an additional overall detection rate between 24.5 % and 44 % by either PET or PET-CT. Metastatic localization (cervical versus extracervical) did not influence the performance. The sensitivity was usually high (> 80 %) but specificity was moderate ranging from 68 % to 88 % at best. If mentioned, the results obtained by fluorodeoxyglucose (FDG)-PET significantly changed the clinical management in approximately one third of the patients studied. In a direct comparison with PET alone, PET-CT did not depict significantly more primary tumors but was able to reduce false positive findings.

ACHIEVEMENTS

To determine the real additional value of PET-CT in the diagnosis of CUP syndrome large prospective studies with more uniform inclusion criteria are needed. Despite the capabilities of FDG-PET-CT there is as yet no evidence that a potentially improved diagnostic algorithm is translated into a better patient outcome.

PRACTICAL RECOMMENDATIONS

Nevertheless, FDG-PET-CT should be performed in all CUP patients where conventional imaging failed to detect a primary site or the results are equivocal. In CUP patients with cervical lymph node metastases PET-CT should be carried out prior to panendoscopy to reduce the number of false negative biopsies.

18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography-Positive Lymph Node Endometriosis Masquerading as Lymph Node Metastasis of a Malignant Tumor

Endometriosis is defined as the presence of endometrium-like tissues at extrauterine sites, most commonly in the abdominal cavity. Lymph node endometriosis is a rare but clinically important type of endometriosis that can mimic lymph node metastasis of a malignant tumor.18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is a useful tool for diagnosing malignant tumors, although it occasionally shows false positive results in tissues with high metabolic activity caused by severe inflammation. In the present report, we describe a case of lymph node endometriosis that mimicked lymph node metastasis of a malignant tumor and showed a positive result on18F-FDG PET/CT. The findings of the present case suggest that lymph node endometriosis could present as swollen lymph nodes with18F-FDG PET/CT-positive results and provide important information for determining an appropriate treatment strategy.

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

Purpose

Carcinoma of unknown primary is one of the ten most frequent cancers worldwide. Its median survival time is less than 10 months. Detecting primary tumour locations and/or occult metastatic lesions may inform definitive treatment and improve patients’ prognosis. We aimed to determine: (1) the sensitivity, specificity and accuracy of 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography; (2) its detection rate of primary tumour locations and occult metastases and (3) factors associated with improved survival times.

Methods

We retrospectively reviewed all cases in the West of Scotland for the period 1 December 2007 to 31 May 2011 that met all our selection criteria: (1) diagnosis of carcinoma of unknown primary; (2) a thorough but negative ‘work-up’ and (3) 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography report. Statistical methods included frequencies, Kaplan-Meier graphs and log-rank tests to compare survival times.

Results

18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography detected primary tumour sites in 19/51 (37.3%) and occult metastases in 28/51 (54.9%) of eligible patients. Its sensitivity, specificity and accuracy were 79.2%, 70.4% and 74.5%, respectively; 20/51 (39.2%) patients died during the study period with a median survival of 8.4 months (range 21.4, SD ± 6.2). The number of metastatic locations was strongly associated with survival ( p = 0.002), but detection of a primary tumour site ( p = 0.174) or histopathology ( p = 0.301) was not.

Conclusion

18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography detected occult metastatic sites in the majority and a primary cancer location in a substantial minority of patients. Our results were comparable with international literature and may indicate that 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography have an early role to improve the accuracy of cancer staging and to optimise carcinoma of unknown primary management.

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.

Initial staging of squamous cell carcinoma of the oral cavity, larynx and pharynx (excluding nasopharynx). Part I: Locoregional extension assessment: 2012 SFORL guidelines

OBJECTIVES

To set out good practice guidelines for locoregional extension assessment of squamous cell carcinoma of the head and neck (excluding nasopharynx, nasal cavities and sinuses).

MATERIALS AND METHODS

A critical multidisciplinary review of the literature on locoregional extension assessment of squamous cell carcinoma of the head and neck was conducted, applying levels of evidence in line with the French health authority's (HAS) literature analysis guide of January 2000.

CONCLUSION

Based on the levels of evidence of the selected articles and on work-group consensus, graded guidelines are set out for clinical, endoscopic and imaging locoregional extension assessment of head and neck 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.

A prospective comparison of 18F-FDG PET/CT and CT as diagnostic tools to identify the primary tumor site in patients with extracervical carcinoma of unknown primary site

BACKGROUND

The aim of the present study was to evaluate prospectively the diagnostic value of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) and conventional CT regarding the ability to detect the primary tumor site in patients with extracervical metastases from carcinoma of unknown primary (CUP) site.

PATIENTS AND METHODS

From January 2006 to December 2010, 136 newly diagnosed CUP patients with extracervical metastases underwent (18)F-FDG PET/CT. A standard of reference (SR) was established by a multidisciplinary team to ensure that the same set of criteria were used for classification of patients, that is, either as CUP patients or patients with a suggested primary tumor site. The independently obtained suggestions of primary tumor sites using PET/CT and CT were correlated with the SR to reach a consensus regarding true-positive (TP), true-negative, false-negative, and false-positive results.

RESULTS

SR identified a primary tumor site in 66 CUP patients (48.9%). PET/CT identified 38 TP primary tumor sites and CT identified 43 TP primary tumor sites. No statistically significant differences were observed between (18)F-FDG PET/CT and CT alone in regard to sensitivity, specificity, and accuracy.

CONCLUSION

In the general CUP population with multiple extracervical metastases (18)F-FDG PET/CT does not represent a clear diagnostic advantage over CT alone regarding the ability to detect the primary tumor site.

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.

Carcinomas of an unknown primary origin--diagnosis and treatment

Carcinomas of an unknown primary origin (CUP) account for 3-5% of all malignancies and are thus among the ten most-frequent cancers worldwide. Having a specific and unique phenotype of early and usually aggressive metastatic dissemination with no identifiable primary tumor, CUP are a challenge for physicians. The diagnostic workup of patients with CUP includes a careful clinical and extensive histopathological examination, as well as the use of imaging techniques. CUP can be divided into favorable and unfavorable subsets. Patients with unfavorable CUP subsets have a poor prognosis with a median survival of approximately 8 months; the optimal chemotherapy regimen for these patients remains to be determined. Although studies have focused on the introduction of new cytotoxic agents with broad-spectrum clinical activity (such as gemcitabine, irinotecan, and taxanes), no randomized trial has provided clear evidence of a survival benefit. Molecular targeted therapies that are approved for other solid tumors are now considered for the treatment of patients with CUP. Molecular diagnostic tools, such as DNA microarray analysis, could help in the search for 'lost' CUP origins. In this Review, we describe the clinical evaluation of patients with CUP, and discuss treatment strategies and outcomes of patients with various CUP subsets.

PET/CT in Neuroendocrine Tumors: Evaluation of Receptor Status and Metabolism

In-111 Octreoscan is considered the gold standard for imaging of neuroendocrine tumors (NET). However, in the absence of morphologic imaging correlation, the exact localisation of the tumor is often difficult. Also the sensitivity of PET imaging is more than Gamma camera (SPECT) imaging. Ga-68 labelled somatostatin analogs (SMS-R) are interesting radiopharmaceuticals for PET receptor imaging of NET. Some other radiopharmaceuticals e.g. F-18 DOPA can also be used to assess metabolism and functional status of NET. The importance of these radiopharmaceuticals, especially SMS-R increases in the absence of any specific biochemical marker or clinical parameter for follow-up of patients after therapy (eg peptide receptor radionuclide therapy, surgery, chemoembolisation, etc). New criteria based on molecular, metabolic and morphologic imaging needs to be developed for correct assessment of response to therapy for these slow-growing, solid tumors.

Diagnosis of Bilateral Tonsil Cancers via Staging PET/CT: Case Report and Review

Diagnostic workup of metastatic head and neck squamous cell carcinoma of unknown primary site has traditionally included CT and/or MRI imaging and endoscopic biopsies. Routine bilateral tonsillectomy is highly controversial and the role of PET/CT is evolving, both for identification of potential primary sites and the detection of distant metastases. We report a case of cervical nodal metastasis of squamous cell carcinoma from an unknown primary site, in which dual-modality PET/CT led to the unexpected diagnosis of synchronous bilateral tonsillar cancers. In addition, PET/CT correctly distinguished pulmonary sarcoidosis from metastatic disease in this patient.

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.

18F-FDG PET/CT as a diagnostic tool in patients with extracervical carcinoma of unknown primary site: a literature review

BACKGROUND

Carcinoma of unknown primary (CUP) represents a heterogeneous group of metastatic malignancies for which no primary tumor site can be identified after extensive diagnostic workup. Failure to identify the primary site may negatively influence patient management. The aim of this review was to evaluate (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) as a diagnostic tool in patients with extracervical CUP.

MATERIALS AND METHODS

A comprehensive literature search was performed and four publications were identified (involving 152 patients) evaluating (18)F-FDG PET/CT in CUP patients with extracervical metastases. All studies were retrospective and heterogeneous in inclusion criteria, study design, and diagnostic workup prior to (18)F-FDG PET/CT.

RESULTS

(18)F-FDG PET/CT detected the primary tumor in 39.5% of patients with extracervical CUP. The lung was the most commonly detected primary tumor site (∼50%). The pooled estimates of sensitivity, specificity, and accuracy of (18)F-FDG PET/CT in the detection of the primary tumor site were 87%, 88%, and 87.5%, respectively.

CONCLUSIONS

The present review of currently available data indicates that (18)F-FDG PET/CT might contribute to the identification of the primary tumor site in extracervical CUP. However, prospective studies with more uniform inclusion criteria are required to evaluate the exact value of this diagnostic tool.

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.

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.

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.

Detection of unknown primary neuroendocrine tumours (CUP-NET) using (68)Ga-DOTA-NOC receptor PET/CT

PURPOSE

This bi-centric study aimed to determine the role of receptor PET/CT using (68)Ga-DOTA-NOC in the detection of undiagnosed primary sites of neuroendocrine tumours (NETs) and to understand the molecular behaviour of the primarily undiagnosed tumours.

METHODS

Overall 59 patients (33 men and 26 women, age: 65 + or - 9 years) with documented NET and unknown primary were enrolled. PET/CT was performed after injection of approximately 100 MBq (46-260 MBq) of (68)Ga-DOTA-NOC. The maximum standardised uptake values (SUV(max)) were calculated and compared with SUV(max) in known pancreatic NET (pNET) and ileum/jejunum/duodenum (SI-NET). The results of PET/CT were also correlated with CT alone.

RESULTS

In 35 of 59 patients (59%), (68)Ga-DOTA-NOC PET/CT localised the site of the primary: ileum/jejunum (14), pancreas (16), rectum/colon (2), lungs (2) and paraganglioma (1). CT alone (on retrospective analyses) confirmed the findings in 12 of 59 patients (20%). The mean SUV(max) of identified previously unknown pNET and SI-NET were 18.6 + or - 9.8 (range: 7.8-34.8) and 9.1 + or - 6.0 (range: 4.2-27.8), respectively. SUV(max) in patients with previously known pNET and SI-NET were 26.1 + or - 14.5 (range: 8.7-42.4) and 11.3 + or - 3.7 (range: 5.6-17.9). The SUV(max) of the unknown pNET and SI-NET were significantly lower (p < 0.05) as compared to the ones with known primary tumour sites; 19% of the patients had high-grade and 81% low-grade NET. Based on (68)Ga-DOTA-NOC receptor PET/CT, 6 of 59 patients were operated and the primary was removed (4 pancreatic, 1 ileal and 1 rectal tumour) resulting in a management change in approximately 10% of the patients. In the remaining 29 patients, because of the far advanced stage of the disease (due to distant metastases), the primary tumours were not operated. Additional histopathological sampling was available from one patient with bronchial carcinoid (through bronchoscopy).

CONCLUSION

Our data indicate that (68)Ga-DOTA-NOC PET/CT is highly superior to (111)In-OctreoScan (39% detection rate for CUP according to the literature) and can play a major role in the management of patients with CUP-NET.

[Utility of PET/CT in evaluation of haed and neck carcinoma--preliminary report on the basis of presented cases]

18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) offers advantages over PET alone, which is limited by poor anatomic localization and CT alone, which provides morphologic data only. Fusion of PET and CT images allows for precise target delineation for head and neck cancer compared with CT alone. The aim of this article is to evaluate the effect of the use of PET/CT in patients with head and neck cancer. We present four patients whose management was influenced by the implementation of combined PET/CT imaging. We conclude that PET/CT allows detection of recurrent neoplasm, carcinoma of unknown origin, second primary sites, distant metastases, tumor surveillance, staging, and planning radiation therapy.

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.