The Utility of 2-Deoxy-2-[F-18]fluoro-d-glucose Positron Emission Tomography in the Investigation of Patients with Disseminated Carcinoma of Unknown Primary Origin

Evaluating the Utility of 18F-FDG PET/CT in Cancer of Unknown Primary

Cancer of unknown primary (CUP) represents a heterogeneous group of metastatic tumors for which standardized diagnostic work-up fails to identify the primary site. We aimed to describe the Peter MacCallum Cancer Centre experience with 18F-FDG PET/CT in extracervical CUP with respect to detection of a primary site and its impact on management. A secondary aim was to compare overall survival (OS) in patients with and without a detected primary site. Methods: CUP patients treated between 2014 and 2020 were identified from medical oncology clinics and 18F-FDG PET/CT records. Information collated from electronic medical records included the suspected primary site and treatment details before and after 18F-FDG PET/CT. Clinicopathologic details and genomic analysis were used to determine the clinically suspected primary site and compared against 2 independent masked reads of 18F-FDG PET/CT images by nuclear medicine specialists to determine sensitivity, specificity, accuracy, and the rate of detection of the primary site. Results: We identified 147 patients, 65% of whom had undergone molecular profiling. The median age at diagnosis was 61 y (range, 20-84 y), and the median follow-up time was 74 mo (range, 26-83 mo). Eighty-two percent were classified as having an unfavorable CUP subtype as per international guidelines.18F-FDG PET/CT demonstrated a primary site detection rate of 41%, resulted in a change in management in 22%, and identified previously occult disease sites in 37%. Median OS was 16.8 mo for all patients and 104.7 and 12.1 mo for favorable and unfavorable CUP subtypes, respectively (P < 0.0001). Median OS in CUP patients when using 18F-FDG PET/CT, clinicopathologic, and genomic information was 19.8 and 8.5 mo when a primary site was detected and not detected, respectively (P = 0.016). Multivariable analysis of survival adjusted for age and sex remained significant for identification of a potential primary site (P < 0.001), a favorable CUP (P < 0.001), and an Eastern Cooperative Oncology Group status of 1 or less (P < 0.001). Conclusion: 18F-FDG PET/CT plays a complementary role in CUP diagnostic work-up and was able to determine the likely primary site in 41% of cases. OS is improved with primary site identification, demonstrating the value of access to diagnostic 18F-FDG PET/CT for CUP patients.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

[Usefulness of (18)F-fluorodeoxyglucose-positron emission tomography-computerized tomography in the identification of the primary tumor in patients with cancer of unknown origin]

BACKGROUND AND OBJECTIVE

We determined the utility of the (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET)-computerized tomography (CT) in the localization of the primary tumor in patients with tumor of unknown origin (TUO).

PATIENTS AND METHOD

(18)F-FDG PET-CT scans, performed between November 2006 and November 2010, in search for the primary tumor in patients with TUO, were retrospectively evaluated. Patients underwent a standard PET-CT, 50-60minutes after intravenous injection of 296-370MBq (18)F-FDG. PET-CT studies were assessed as pathological, with/without identification of the primary tumour and no pathological. Final diagnosis was established by histological confirmation and/or clinical/radiologic follow-up longer than 6 months.

RESULTS

We studied 74 patients (59 males, 15 females), with ages ranging from 41-89 years. In 38 (51%) patients the PET-CT assessed the correct origin of the primary tumour. In 8 cases, a histological confirmation in the primary lesion was obtained. In 4 patients the PET-CT showed a false positive result.

CONCLUSION

PET-CT scanning identified 51% of the primary sites in our sample of patients.

Site-specific cancer deaths in cancer of unknown primary diagnosed with lymph node metastasis may reveal hidden primaries

Cancer of unknown primary site (CUP) is a fatal cancer ranking among the five most common cancer deaths. CUP is diagnosed through metastases, which are limited to lymph nodes in some patients. Cause-specific survival data could guide the search for hidden primary tumors and help with therapeutic choices. The CUP patients were identified from the Swedish Cancer Registry between 1987 and 2008; 1,444 patients had only lymph node metastasis of defined histology (adenocarcinoma, squamous cell or undifferentiated). Site-specific cancer deaths were analyzed by lymph node location and histology. Kaplan-Meier survival curves were compared with metastatic primary cancer at related sites. Among the patients with metastasis to head and neck lymph nodes, 117 (59.1% of the specific cancer deaths) died of lung tumors. Patients with axillary lymph node metastasis died of lung and breast tumors in equal proportions (40.2% each). Also, squamous cell CUP in head and neck lymph nodes was mainly associated with lung tumor deaths (53.1%). With a few exceptions, survival of CUP patients with lymph node metastasis was indistinguishable from survival of patients with metastatic primary cancer originating from the organs drained by those nodes. The association between lymph node CUP metastases with cancer deaths in the drained organ and the superimposable survival kinetics suggests that drained organs host hidden primaries. Importantly, half of all site-specific cancer deaths (266/530) were due to lung tumors. Thus, an intense search should be mounted to find lung cancer in CUP patients with lymph node metastases.

Successful resection of advanced pancreatic tail cancer after neoadjuvant gemcitabine chemotherapy: report of a case

Pancreatic cancer with distant metastasis is not an indication for surgery, and the median survival of these patients is less than 3 months. We report the case of a patient who has survived for 21 months without any signs of recurrence after resection of advanced pancreatic cancer following a course of chemotherapy with gemcitabine (GEM). A 75-year-old man was hospitalized for anorexia and emaciation. Examinations showed pancreatic cancer with distant peritoneal metastasis. After the main tumor and metastasis had been shrunk by GEM chemotherapy, we performed distal pancreatectomy combined with splenectomy. Microscopically, the main tumor was confirmed as moderately differentiated tubular adenocarcinoma with interstitium and fibrosis. The radicality of the surgery was R0, according to the TNM classification of the UICC. The patient recovered well and has had no clinical symptoms for 40 months since the initial chemotherapy. This case suggests that multidisciplinary treatment with GEM may prolong the survival of some patients with unresectable pancreatic cancer.

The role of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography in disseminated carcinoma of unknown primary site

BACKGROUND

The authors conducted a comprehensive review of the efficacy of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography (FDG-PET) in the detection of primary tumors in patients with disseminated carcinoma of unknown primary site.

METHODS

Ten studies (involving a total of 221 patients) tat were published between 1998 and 2006 were reviewed. Each study evaluated the role of FDG-PET in the detection of unknown primary tumors after a conventional diagnostic workup. Although 94% of patients had a single site of metastases, the studies otherwise were very heterogeneous in the studied population, study design, and additional diagnostic workup.

RESULTS

In 41% of patients, FDG-PET detected primary tumors that were not apparent after conventional workup. In this group of patients, the overall sensitivity, specificity, and accuracy rates of FDG-PET in detecting unknown primary tumors were 91.9%, 81.9%, and 80.5%, respectively. FDG-PET imaging also led to the detection of previously unrecognized metastases in 37% of patients. Lung cancers represented 59% of the detected tumors. FDG-PET had a notably high false-positive rate (58.3%) in tumors of the lower digestive tract. FDG-PET altered the clinical management in 34.7% of patients. Most of those patients (53%) received specific chemotherapy for lung and pancreatic cancers; whereas 12% received specific therapy for breast, ovarian, and prostate cancers; and 14% underwent surgery with curative intent.

CONCLUSIONS

FDG-PET was an efficient method for detecting primary tumors that were undetected by other modalities and was sensitive for the detection of previously unrecognized metastases. FDG-PET significantly changed clinical management in approximately one-third of the patients studied.

Positron emission tomography and leiomyomas: Clinicopathologic analysis of 3 cases of PET scan-positive leiomyomas and literature review

INTRODUCTION

Studies have suggested that PET scans can differentiate between leiomyomas and leiomyosarcomas. Our experience, however, shows that PET scan-positive smooth muscle tumors are not necessarily malignant.

CASE REPORTS

Three patients with cancer underwent PET imaging. In all three, the most worrisome finding was a PET scan-positive uterine tumor. After surgical extirpation, all three uterine tumors were found to be benign smooth muscle neoplasms.

DISCUSSION

To explore the potential reason these tumors were positive on PET imaging, we performed a detailed histopathologic and immunohistochemical study of all specimens. Pathologic evaluation revealed a leiomyoma, a cellular leiomyoma, and a stromomyoma. There was no association between an increased Ki67 (proliferative) index and positivity on PET imaging. Increased vascularity, however, appeared to be a feature common to the leiomyomas that were PET-positive.

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.