Positron emission tomography (PET) and other nuclear medicine modalities in staging gastrointestinal cancer

Usefulness of F-18-fluorodeoxyglucose positron emission tomography to confirm suspected pancreatic cancer: a meta-analysis

INTRODUCTION

Pancreatic cancer is among the five most lethal malignancies in the world. Unfortunately, many malignant tumors go undetected by the current primary diagnostic tools. (18)FDG-PET and (18)FDG-PET/CT might be useful to confirm suspected pancreatic cancer.

METHODS

A meta-analysis was performed using all major search engines. Methodological quality of included studies was assessed as well as quality of the PET-protocol. The following pooled estimates served as primary outcome measures: sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy.

RESULTS

Thirty-five studies were included. Pooled estimates for (18)FDG-PET were: sensitivity 90%, specificity 76%, PPV 90%, NPV 76% and accuracy 86%. Pooled estimates for (18)FDG-PET/CT were: sensitivity 90%, specificity 76%, PPV 89%, NPV 78% and accuracy 86%. The pooled sensitivity and specificity for (18)FDG-PET to differentiate between pancreatic cancer and chronic pancreatitis were 90% and 84%, respectively.

CONCLUSION

Both (18)FDG-PET and (18)FDG-PET/CT offer no benefit over the current primary diagnostic tools in diagnosing pancreatic cancer. However, the (18)FDG-PET/CT systems are still improving. We should investigate the sensitivity and specificity of these new systems while reevaluating the tradeoff between false positive and false negative results. Yet, (18)FDG-PET/CT may have a role in the staging of pancreatic cancer, in survival prediction, and may add to other diagnostic information, like histology.

Skeletal Muscle Metastases in a Patient With Neuroendocrine Tumor

Carcinoid tumors are rare but diverse group of malignancies that arise from neuroendocrine cells. Skeletal muscle metastasis is exceedingly rare and is associated with a poor prognosis. We report a case of carcinoid tumor of the ileocecal with skeletal muscle metastasis. We also review available case reports of carcinoid tumors metastasizing to the muscle.

Using 18F-fluorodeoxyglucose positron emission tomography to monitor clinical outcomes in patients treated with neoadjuvant chemo-radiotherapy for locally advanced pancreatic cancer

BACKGROUND

Pancreatic cancer ranks as the fourth leading cause of cancer death in the United States with 5-year survival ranging from 1% to 5%. Positron emission tomography (PET) is a metabolic imaging system that is widely used for the initial staging of cancer and detecting residual disease after treatment. There are limited data, however, on the use of this molecular imaging technique to assess early tumor response after treatment in pancreatic cancer.

METHODS

The objective of the study was to explore the relationship of early treatment response using the F-fluorodeoxyglucose (FDG) PET with surgical outcome and overall survival in patients with locally advanced pancreatic cancer. FDG-PET measurements of maximum standardized uptake value and kinetic parameters were compared with the clinical outcome.

RESULTS

Twenty patients were enrolled in the study evaluating neoadjuvant induction chemotherapy followed by concurrent chemoradiotherapy (chemo-RT) for locally advanced pancreatic cancer. All 20 patients had prestudy PET scans and a total of fifty PET scans were performed. Among patients who were PET responders (> or =50% decrease in standardized uptake value after cycle 1), 100% (2/2) had complete surgical resection. Only 6% (1/16) had surgical resection in the PET nonresponders (<50% decrease). Two patients did not have the second PET scan because of clinical progression or treatment toxicity. Mean survival was 23.2 months for PET responders and 11.3 months for nonresponders (P = 0.234). Similar differences in survival were also noted when response was measured using Patlak analysis.

CONCLUSIONS

FDG-PET can aid in monitoring the clinical outcome of patients with locally advanced pancreatic cancer treated with neoadjuvant chemo-RT. FDG-PET may be used to aid patients who could have complete surgical resection as well as prognosticate patients' survival.

Non-natural amino acids for tumor imaging using positron emission tomography and single photon emission computed tomography

Amino acids are required nutrients for proliferating tumor cells, and amino acid transport is upregulated in many tumor types. Studies of radiolabeled amino acids in animals and humans demonstrate that amino acid based tracers have advantageous characteristics relative to 2-[(18)F]fluoro-2-deoxyglucose in certain tumors, particularly brain gliomas. Non-natural amino acids for tumor imaging generally have greater metabolic stability and can be labeled with longer-lived radionuclides for positron emission tomography and single photon emission computed tomography such as fluorine-18 and iodine-123. Amino acids enter cells via amino acid transport with varying selectivity based on their chemical structure. This review focuses on the rationale, biological basis, current status and future prospects of radiolabeled non-natural amino acids for tumor imaging and discusses various classes of these compounds including aromatic, alicyclic and alpha,alpha-dialkyl amino acids.

[PET/CT for colorectal and hepatic tumors]

This contribution presents clinical and technical aspects of combining positron emission tomography (PET) and computed tomography (CT) for patients with colorectal tumors and characterization of unclear liver foci. In which manner and for which patients combined PET/CT is superior to PET or CT alone is also discussed. PET/CT can fulfil most prerequisites for imaging in pre- and postoperative management of patients with colorectal tumors and best meets the desire for optimal imaging procedures. Some of the disadvantages encountered in frequently employed CT can be overcome by the combination of PET and CT while increasing both sensitivity in detecting lesions and specificity in their characterization. Questions regarding treatment response offer an opportunity for devising novel study concepts and initiating research on new PET tracers. Although few publications are available, we are of the opinion that the combination of functional and anatomical imaging provided by PET/CT can improve both preoperative management and aftercare. To this end, however, optimum cooperation between practitioners of nuclear medicine and radiology is imperative.

Restaging after neoadjuvant chemoradiotherapy for rectal adenocarcinoma: role of F18-FDG PET

Multimodality treatment of loco-regional advanced rectal cancer has demonstrated to improve local control and overall survival. Proctoscopy, digital rectal examination (DRE), computer tomography (CT), endorectal ultrasound (ERUS), and magnetic resonance imaging (MRI) cannot correctly detect downstaging in rectal tumors after chemo radiation therapy (CRT). New imaging techniques, like 18F-FDG PET, may play some role in predicting the pathologic response to CRT before surgical resection. Aim of the present study was to further investigate the accuracy and predictive value of 18F-FDG PET in a large series of patients with rectal cancer treated with preoperative intensified CRT. Between January 2000 and December 2003, 81 patients with histologically proven adenocarcinoma in clinical stage II-III disease, according to criteria of TNM classification, were included in this study. All patients were submitted to diagnostic staging workup with DRE, proctoscopy with biopsy, ERUS, CT scan of the abdomen and pelvis or pelvic MRI plus liver ultrasonography, coloscopy or barium colonic enema. One month later the end of CRT all patients were submitted to diagnostic restaging work-up (DRW) and 18F-FDG PET. Surgery was performed 8-9 weeks after the end of CRT and pathologic stage was defined. Moreover a pathologic assessment of tumor regression was made with tumor regression grade score (TRG). PET correctly identified 22/28 (79% specificity) patients with complete pathologic response (pCR). However, sensitivity was 45% (24/53) while PPV, and NPV were equal to 77 and 43%, respectively. Total PET accuracy rate was 56%. PET sensitivity increased from 45 to 56% if the end-point was pCR, or TRG score, respectively. The best correlation was found between PET findings and pathologic stage (P <0.01) or TRG score (P <0.01). The accurate identification of rectal cancer patients with major pathological response after preoperative CRT further supports the necessity of designing prospective studies with new and more accurate was imaging technologies with the main object of offering conservative treatment in responder patients.

Modern hepatic imaging

This article provides a brief overview of the current status of commonly employed diagnostic techniques--US, CT, MR, and PET--for the evaluation of liver metastases and HCC as well as a description of imaging in RF ablation and liver transplantation. The various advantages and limitations of the techniques have been outlined. At the present time, at our center, MRI is used most often to evaluate these liver pathologies, due to its high accuracy for lesion detection and characterization.

Hilar cholangiocarcinoma: surgical and endoscopic approaches

HCCa remains an uncommon malignancy, though increasing use of more radical surgery has led to prolonged survival in those patients who undergo curative resection. The extent of these resections suggest that the best results are likely to be obtained in centers with the resources and experience to conduct these operations in a safe fashion. Until major advances in the systemic therapy of HCCa are made, however, the management should focus on optimal preoperative imaging and palliation of jaundice with improvement in quality of life.

[Positron emission tomography for preoperative lymph node diagnosis in esophageal carcinoma]

BACKGROUND

Exact preoperative staging is a prerequisite for the indication and the choice of appropriate operative technique for patients with esophageal carcinoma. The objective of this prospective study was to assess whether positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) increases the accuracy of preoperative lymph node staging with standard computed tomography (CT) and thus leads to a different surgical approach.

PATIENTS AND METHODS

Fifty-eight patients with carcinoma of the esophagus (46 men and 12 women) with a median age of 61 years underwent FDG-PET imaging of the neck, chest, and abdomen as well as CT of the chest and abdomen. Sensitivity, specificity, and accuracy were calculated for both imaging techniques to evaluate the detection of histologically verified lymph node metastases.

RESULTS

The FDG-PET showed higher specificity, whereas CT proved to be more accurate for detecting lymph node metastases not only of the abdomen (73% vs 59%) but also of the thorax (73% vs 63%). Resections were transhiatal in 23 patients and transthoracal in 16. As a supplement to conventional CT diagnostic procedure, FDG-PET was not decisive for the surgical approach.

CONCLUSIONS

Altogether, pretherapeutical PET imaging did not increase the accuracy of lymph node staging for our patients with esophageal carcinoma, which had already been defined through CT. Therefore, no new consequences resulted for the surgical procedure. Due to the high costs involved with PET investigation, lymph node staging with it is momentarily indicated mainly for clinical studies and when CT does not offer unequivocal results. Increased sensitivity of the already advantageous whole-body FDG-PET imaging by means of tumor-affinitive radiopharmaceuticals and optimized apparatus resolution could lead to new indications for this staging procedure.

Positron emission tomography for staging esophageal cancer: does it lead to a different therapeutic approach?

Accurate preoperative staging is essential for the indication and selection of the appropriate surgical procedure in patients with esophageal cancer. The present prospective study was designed to determine if the preoperative use of (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) increases the accuracy of staging esophageal cancer compared with computed tomography (CT) and if it thereby leads to a different therapeutic approach. A total of 58 patients, 46 men and 12 women (mean age 61 years), with histologic proof of esophageal carcinoma underwent FDG-PET of the neck, chest, and abdomen, as well as CT of the chest and abdomen, to determine tumor stage. FDG-PET and CT data were compared with each other and with pathohistologic findings. Sensitivity, specificity, and overall accuracy for detecting histologically verified lymph node and distant metastases were calculated for FDG-PET and CT. FDG-PET showed a higher specificity, whereas CT had higher accuracy for detecting both abdominal (73% vs. 59%) and thoracic (73% vs. 63%) lymph node metastases. The accuracy of detecting blood-borne and lymphatic distant metastases was identical for CT and FDG-PET imaging (50%). FDG-PET had a higher specificity than CT (87% vs. 13%) but lower sensitivity (35% vs. 67%). FDG-PET did not provide new information on the indication for surgery, nor was it helpful for choosing the appropriate surgical procedure in patients with esophageal carcinoma. In view of the relatively high cost of FDG-PET examinations, the use of this modality is indicated primarily in patients with inconclusive CT findings or for scientific research projects. Higher sensitivity as a result of tumor-affinity radiopharmaceuticals and optimized apparatus resolution, in addition to the advantages offered by whole-body PET scanning, may lead to new indications for this staging procedure in the future.