Endocrine tumors: the evolving role of positron emission tomography in diagnosis and management

Duodenal neuroendocrine tumor-tertiary care centre experience: A case report

BACKGROUND

Neuroendocrine neoplasms (NENs) are a heterogeneous group of neoplasms arising from neuroendocrine cells, which contribute a small fraction of gastrointestinal malignancies. Duodenal neuroendocrine tumors (dNETs) represent 2% of all gastroenteropancreatic NENs. NENs are heterogeneous in terms of clinical symptoms, location, and prognosis. Non-functional NETs are mostly asymptomatic and need a high degree of clinical suspicion. Diagnosis of NETs is by endoscopic, endosonographic biopsy, and histopathological examination with immunohistochemistry staining for synaptophysin and chromogranin A.

CASE SUMMARY

We present case reports of 5 patients obtained over a period of 10 years in our center with dNETs. One patient had moderately differentiated NET and the remaining four had well-differentiated NET. Surveillance endoscopy was recommended in all the patients and is kept under regular follow-up after performing endoscopic therapy using endoscopic mucosal resection in 4 of them and one patient was advised to undergo a Whipple procedure.

CONCLUSION

Recently, the number of reported cases of NETs has increased due to advancements in diagnostic modalities and prevalence because of longer survival duration. The management differs based on the site, size, proliferation grade, and locally invasive pattern. They are slow-growing tumors with a good overall prognosis. The prognosis correlates with local lymph node status and metastasis.

Metabolic In Vivo Visualization of Pituitary Adenomas: a Systematic Review of Imaging Modalities

OBJECTIVE

Pituitary adenomas (PAs) are the most common intrasellar mass. Functional PAs constitute most of pituitary tumors and can produce symptoms related to hormonal overproduction. Timely and accurate detection is therefore of vital importance to prevent potentially irreversible sequelae. Magnetic resonance imaging is the gold standard for detecting PAs, but is limited by poor sensitivity for microadenomas and an inability to differentiate scar tissue from tumor residual or predict treatment response. Several new modalities that detect PAs have been proposed.

METHODS

A systematic review of the PubMed database was performed for imaging studies of PAs since its inception. Data concerning study characteristics, clinical symptoms, imaging modalities, and diagnostic accuracy were collected.

RESULTS

After applying exclusion criteria, 25 studies of imaging PAs using positron emission tomography (PET), magnetic resonance spectroscopy (MRS), and single photon emission computed tomography were reviewed. PET reliably detects PAs, particularly where magnetic resonance imaging is equivocal, although its efficacy is limited by high cost and low availability. Single photon emission computed tomography possesses good sensitivity for neuroendocrine tumors but its use with PAs is poorly documented. MRS consistently detects cellular proliferation and hormonal activity, but warrants further study at higher magnetic field strength.

CONCLUSIONS

PET and MRS appear to have the strongest predictive value in detecting PAs. MRS has the advantage of low cost, but the literature is lacking in specific studies of the pituitary. Due to high recurrence rates of functional PAs and low sensitivity of existing diagnostic workups, further investigation of metabolic imaging is necessary.

FDG PET/CT Scan and Functional Adrenal Tumors: A Pilot Study for Lateralization

BACKGROUND

Patients with Cushing's Syndrome (CS) and Conn's Syndrome with bilateral adrenal masses pose a dilemma. Uptake of 18F-FDG by hyperfunctioning adrenal glands has not been previously reported and may help lateralize. The aim was to determine if 18F-FDG PET/CT scan could identify hyperfunctioning adrenal masses and determine a biological basis for uptake.

METHODS

Patients with nonfunctional adenomas (n = 9), CS (n = 11), and Conn's syndrome (n = 4) underwent an 18F-FDG PET/CT scan with a volume of interest circumscribing each mass to obtain a maximal standardized uptake value (SUVmax). Thirty-two adrenal masses were analyzed. Genome-wide expression data from an independent cohort were analyzed in nonfunctioning adenomas (n = 20), Conn's syndrome (n = 29), and CS (n = 24) focusing on GLUT genes. For genes differentially expressed, immunohistochemistry was performed on tissue samples.

RESULTS

Cortisol-secreting masses (n = 16) had a higher average SUVmax of 5.9 compared to nonfunctioning masses (n = 11, average SUVmax 4.2) and aldosterone-hypersecreting masses (n = 5, average SUVmax 3.2) (p = 0.007). SUVmax cut-off of 5.33 had 50.0% sensitivity and 81.8% specificity in localizing a cortisol-secreting mass. GLUT3 expression was 2.19-fold higher in patients with CS compared to patients with nonfunctioning adenomas (p = 0.003) and 2.16-fold higher in patients with CS compared to Conn's syndrome (p = 0.006). GLUT3 immunohistochemistry showed 2.2-fold higher staining in CS tumor samples compared to nonfunctioning adenomas.

CONCLUSIONS

Differential 18F-FDG PET/CT uptake was observed in patients with nonfunctioning, aldosterone-hypersecreting, and cortisol-secreting masses. GLUT3 overexpression in cortisol-secreting tumor likely accounts for the differential uptake. Future larger cohort studies will need to be conducted to determine if 18F-FDG PET/CT uptake can lateralize cortisol-secreting adrenal masses in patients with bilateral adrenal masses.

Guidelines for biomarker testing in gastroenteropancreatic neuroendocrine neoplasms: a national consensus of the Spanish Society of Pathology and the Spanish Society of Medical Oncology

The annual incidence of neuroendocrine tumours in the Caucasian population ranges from 2.5 to 5 new cases per 100,000 inhabitants. Gastroenteropancreatic neuroendocrine tumours is a family of neoplasms widely variable in terms of anatomical location, hormone composition, clinical syndromes they cause and in their biological behaviour. This high complexity and clinical heterogeneity, together with the known difficulty of predicting their behaviour from their pathological features, are reflected in the many classifications that have been developed over the years in this field. This article reviews the main tissue and clinical biomarkers and makes recommendations for their use in medical practice. This document represents a consensus reached jointly by the Spanish Society of Medical Oncology (SEOM) and the Spanish Society of Pathology (SEAP).

¹⁸F-FDG-PET and ¹⁸F-FDG-PET/CT in the detection of recurrent or metastatic medullary thyroid carcinoma: a systematic review and meta-analysis

The aim of this study was to investigate diagnostic performance of (18) F-fluorodeoxyglucose position emission tomography (FDG-PET) and PET/computed tomography (PET/CT) for detection of recurrent or metastatic medullary thyroid carcinoma (MTC) in patients after surgery with a meta-analysis. MEDLINE and EMBASE databases were searched for relevant articles. Two investigators independently extracted the data about study characteristics and examination results. Pooled estimates of sensitivity of FDG-PET or FDG-PET/CT were obtained. Fifteen studies met all inclusion criteria. The sensitivity of FDG-PET ranged from 0.47 (95% confidence intervals (CI): 0.21-0.73) to 0.96 (95%CI: 0.86-0.99), the sensitivity of FDG-PET/CT ranger from 0.47 (95% CI: 0.31-0.64) to 0.80 (95% CI: 0.65-0.90). The pooled sensitivities of FDG-PET and PET/CT were 0.68 (95% CI: 0.64-0.72) and 0.69 (95% CI: 0.64-0.74), respectively. There was no statistic significant between FDG-PET and PET/CT. Our results indicate that FDG-PET or FDG-PET/CT has reasonable sensitivity in detecting recurrent or metastatic MTC after primary surgery. However, no single diagnostic technique is able to reliably demonstrate the full extent of disease in patients with recurrent or metastatic MTC, the combination of cross-sectional radiography with FDG-PET or PET/CT is recommended.

Role of (18)F-choline PET/CT in evaluation of patients with prostate carcinoma

Background

Choline presents a high affinity for malignant prostate tissue. It can be labelled with positron emitting ¹⁸F, and used for the evaluation of patients with prostate carcinoma by PET/CT imaging. The aim of this paper is to summarise our experience with fluoromethylcholine (¹⁸F-choline) PET/CT in patients with prostate cancer.

Methods

In 4 months we investigated the patients with histopathological (or cytological) confirmed prostate cancer. Two observers evaluated the early and late ¹⁸F-choline PET images in correlation with corresponding localising CT images and using the semiquantitative standard uptake value (SUV) calculation.

Results

The ¹⁸F-choline PET/CT was made in 50 patients with prostate cancer. There were 18 patients after radical prostatectomy and 32 without surgery. In all patients without surgery the pathological uptake was seen in the prostate. In 14 (44 %) patients of this group there was evidence of metastatic spread in local or distant lymph nodes and/or bones. In out of 18 patients after radical prostatectomy the local recurrence was detected in 6 patients (33%) and distant metastases were present in 2 patients (10%).

Conclusions

¹⁸F-choline PET/CT seems to be useful imaging modality in patients with prostate carcinoma; it can demonstrate spread of the disease preoperatively and detect the local recurrence after radical prostatectomy.