Positron Emission Tomography in Lung Cancer

Reports on positron emission tomography have become more common in the oncology literature. After a short introduction to positron emission tomography, this review will look at the data relating to the use of this technology in the diagnosis, the staging, and the posttreatment evaluation of patients with lung cancer and will discuss its potential role in these evaluations.     

Advantages of Diffusion-Weighted Imaging Over Positron Emission Tomography-Computed Tomography in Assessment of Hilar and Mediastinal Lymph Node in Lung Cancer

Background

The significance of diffusion-weighted imaging (DWI) is uncertain for the diagnosis of nodal involvement. The purpose of this study was to examine diagnostic capability of DWI compared with PET-CT for nodal involvement of lung cancer.

Methods

A total of 160 lung cancers (114 adenocarcinomas, 36 squamous cell carcinomas, and 10 other cell types) were analyzed in this study. DWI and PET-CT were performed preoperatively.

Results

The optimal cutoff values to diagnose metastatic lymph nodes were 1.70 × 10^?3 mm²/s for ADC value and 4.45 for SUVmax. DWI correctly diagnosed N staging in 144 carcinomas (90 %) but incorrectly diagnosed N staging in 16 (10 %) [3 (1.9 %) had overstaging, 13 (8.1 %) had understaging]. PET-CT correctly diagnosed N staging in 133 carcinomas (83.1 %) but incorrectly diagnosed N staging in 27 (16.8 %) [4 (2.5 %) had overstaging, 23 (14.4 %) had understaging]. Sensitivity, accuracy, and negative predictive value for N staging by DWI were significantly higher than those by PET-CT. Of the 705 lymph node stations examined, 61 had metastases, and 644 did not. The maximum diameter of metastatic lesions in lymph nodes were 3.0 ± 0.9 mm in 21 lymph node stations not detected by either DWI or PET-CT: 7.2 ± 4.1 mm in 39 detected by DWI, and 11.9 ± 4.1 mm in 24 detected by PET-CT. There were significant differences among them. The sensitivity (63.9 %) for metastatic lymph node stations by DWI was significantly higher than that (39.3 %) by PET-CT. The accuracy (96.2 %) for all lymph node stations by DWI was significantly higher than that (94.3 %) by PET-CT.

Conclusions

DWI has advantages over PET-CT in diagnosing malignant from benign lymph nodes of lung cancers.     

Fluorodeoxyglucose–Positron Emission Tomography Imaging Versus Sentinel Node Biopsy in the Primary Staging of Melanoma Patients

BACKGROUND: Positron emission tomography (PET) imaging is superior to conventional techniques for the evaluation of patients with stage III and stage IV cutaneous melanoma. Several studies have highlighted the advantages of this noninvasive technique for the assessment of lymph node involvement. OBJECTIVE: To compare PET imaging with sentinel node biopsy for primary staging of cutaneous melanoma and to discuss the technical limitations of PET scanning. METHODS: Twenty-five consecutive patients with a histologic diagnosis of melanoma with a Breslow thickness equal or greater to 1 mm underwent a preoperative PET to assess lymph node involvement. RESULTS: Sentinel node biopsy and PET showed a sensitivity of 100% and 22%, respectively, in the identification of lymph node metastases. CONCLUSION: PET is not a sensitive technique for the primary staging of cutaneous melanoma.     

Use of Positron Emission Tomography in Assessing Hidden Extrathoracic Metastasis in Non Small Cell Lung Cancer

IntroductionPositron emission tomography combined with computed axial tomography (PET/CT) is used for staging non small cell lung cancer (NSCLC). This study aims to describe PET/CT findings of unsuspected extrathoracic metastasis when used in mediastinal evaluation of patients with apparently resectable NSCLC.Patients and methodProspective and concurrent study including all NSCLC patients between June 2004 and November 2006 who underwent PET/CT after considering them as candidates for surgery, with resectable disease after bronchoscopy, thorax and abdominal CT, brain CT and bone gammagraphy evaluation, if metastasis at these locations were suspected. Metastasis were confirmed histopathologically or assumed when they had a compatible evolution.ResultsA total of 91 patients with NSCLC underwent PET/CT. In 24 of them (26%) at least one suspicious extrathoracic uptake was seen. In 7 patients (7.7%) those uptakes were NSCLC extrathoracic metastasis hidden from conventional staging. In 3 of these cases (13.1%) extrathoracic uptakes corresponded to metacrhonous tumours or pre-malignant conditions. Benign lesions were found in 12 patients (13.1%), and in 2 cases (2.2%) the uptake origins were undetermined.ConclusionsPET/CT is a complementary diagnosis method for assessing hidden metastases which could modify the therapeutical approach in patients otherwise suitable for surgery.     

New Sentinel Node Mapping Technologies for Early Gastric Cancer

The sentinel node (SN) concept has revolutionized the surgical staging of both melanoma and breast cancer over the past two decades. The application of this concept can yield benefits for patients by preventing various complications related to unnecessary prophylactic regional lymph node dissection in patients with cancer-negative SNs. Clinical application of SN mapping in patients with early gastric cancer has been a controversial issue for years. However, a recent meta-analysis and a prospective multicenter trial of SN mapping for early gastric cancer have shown acceptable SN detection rates and accuracy of determination of lymph node status. For early stage gastric cancer such as cT1N0M0, for which a better prognosis can be achieved through conventional surgical approaches, the establishment of individualized, minimally invasive treatments that may retain the patients’ quality of life should be the next surgical challenge. Although there are many unresolved technical issues, laparoscopic SN biopsy with laparoscopic minimized gastrectomy or endoscopic mucosal resection/endoscopic submucosal dissection has the potential to achieve this goal.     

Lymphatic Mapping and Sentinel Node Biopsy of Operable Breast Cancer

The aim of this study was to evaluate the reliability and accuracy of sentinel node biopsy for invasive breast cancer and the predictability of axillary node status. Between January 1996 and June 1997 a total of 73 patients underwent patent blue dye lymphatic mapping and sentinel node biopsy followed by standard (level I and II) axillary node dissection (one bilateral procedure). The sentinel node was identified in 82.4% (61/74) of the cases and was predictive of axillary status in 96.7% (59/61). The false-negative rate of the procedure was 8.0% (2/25). The sentinel node was involved in 37.7% (23/61) and was the only one invaded in 30.4% (7/23). The sensitivity of the procedure was 92% (CI95% 74-99%) and its specificity 100%. It is currently considered to be an attractive new procedure undergoing evaluation in prospective controlled trials. This study confirmed the reliability and reproducibility of intraoperative lymphatic mapping and sentinel node biopsy. This is the first step toward a new era of minimally invasive axillary surgery for breast cancer.     

Sentinel Lymph Node Mapping in Colon Cancer: Current Status

Background The primary role of sentinel lymph node (SLN) mapping in colon cancer is to increase the accuracy of nodal staging by identifying those lymph nodes with the greatest potential for harbouring metastatic disease. Ultrastaging techniques aim to identify the otherwise undetected metastases. Until now, no consensus exists as to the most optimal procedure in patients with colon cancer. Methods A systematic literature search on the value of different SLN mapping techniques in patients with colon cancer was performed using the electronic search engine PubMed. Prospective studies published before 1 December 2005 were included and further articles were selected by cross-referencing. The results of different techniques using either blue dye or radiocolloid, were investigated. Results The literature search yielded 17 relevant articles. SLN mapping using blue dye was described in 15 studies. Two studies reported the results of SLN mapping using a combination of blue dye and radiocolloid. The reported results on identification rate varied between 71 and 100%. Accuracy rates were between 78 and 100%, sensitivity rates between 25 and 100% and true upstaging rates between 0 and 26%. The results were not affected by the addition of radiocolloid to blue dye. Conclusions Sentinel lymph node mapping in patients with colon cancer remains an experimental procedure with varying results. Further evaluation may lead to a standardized technique that offers the potential for significant upstaging of stage II patients. This may have important implications as to tailor adjuvant chemotherapeutic regimens in these patients. Robbert J. de Haas and Dennis A. Wicherts have contributed equally and are mentioned alphabetically.     

Diagnosis and Staging of Pancreatic Cancer by Positron Emission Tomography

The detection of pancreatic cancer or the discrimination between pancreatic cancer and chronic pancreatitis remains an important diagnostic problem. Several imaging modalities are now used to diagnose pancreatic cancer, including transabdominal ultrasonography (US), contrast-enhanced computed tomography (CT), magnetic resonance imaging (MRI), endoscopic retrograde cholangiopancreatography (ERCP), endoscopic ultrasonography, and selective angiography. None of these six methods is perfect: Each has advantages and disadvantages, and their sensitivity and specificity are in a high range. In 1990 positron emission tomography (PET) was first applied to diagnose pancreatic cancer. This new diagnostic modality is based on functional changes in the pancreatic cancer cells caused by enhanced glucose metabolism. Increased glucose utilization is one of the characteristics of malignantly transformed cells, independent of their origin. The technical development of PET has allowed this new procedure to be used for clinical evaluation. Using 2-(¹⁸F)-fluoro-2-deoxy-d-glucose, PET can identify pancreatic cancer and differentiate pancreatic cancer from chronic pancreatitis with a sensitivity of 85% to 98% and a specificity of 53% to 93%. However, high sensitivity and high specificity are strongly dependent on the tumor stage. At present PET is still experimental and is available only in specialized centers. It may represent a new and noninvasive diagnostic procedure for the detection and the staging of pancreatic cancer. Further clinical studies, especially including patients with early tumor stages (small tumor size), are needed. This review discusses the possibilities and limits of PET and evaluates its importance in the future.