The role of CT and MRI in staging of the mediastinum

Lung cancer staging: clinical and radiologic perspectives

Published in 2009, the 7th edition of the American Joint Committee on Cancer TNM staging system is the culmination of an extensive worldwide initiative to standardize and validate lung cancer staging. Unlike prior editions, the new staging system is now inclusive of small cell carcinoma and carcinoid tumors. In addition, significant changes were made to the T and M descriptors, resulting in improved prognostic stratification of disease. This review article highlights these changes, the rationale for their inclusion in the new staging manual, and the role of the radiologist in determining stage.

Assessment of mediastinal tumors with diffusion-weighted single-shot echo-planar MRI

PURPOSE

To assess the role of diffusion-weighted single-shot echo-planar magnetic resonance imaging (MRI) in patients with mediastinal tumors.

METHODS

Prospective study was conducted on 45 consecutive patients (29 male, 16 female, age 22-66 years, mean 41 years) with mediastinal tumor. They underwent diffusion-weighted single-shot echo-planar MRI of the mediastinum with a b-factor of 0, 300, and 600 sec/mm(2). The apparent diffusion coefficient (ADC) value of the mediastinal tumor was correlated with the histopathological findings.

RESULTS

The mean ADC value of malignant mediastinal tumors was 1.09 +/- 0.25 x 10(-3) mm(2)/sec, and of benign tumors was 2.38 +/- 0.56 x 10(-3) mm(2)/sec. There was a significant difference in the mean ADC value between malignant and benign tumors (P = 0.001) and within different grades of malignancy (0.001). When an ADC value of 1.56 x 10(-3) mm(2)/sec was used as a threshold value for differentiating malignant from benign tumor, the best results were obtained with an accuracy of 95%, sensitivity of 96%, specificity of 94%, positive predictive value of 94%, negative predictive value of 96%, and area under the curve of 0.938.

CONCLUSION

The ADC value is a noninvasive parameter that can be used for differentiation of malignant from benign mediastinal tumors and grading of mediastinal malignancy.

Intrathoracic paraspinal malignant peripheral nerve sheath tumor

Schwannoma is the most common nerve sheath tumor in the posterior mediastinum, whereas intrathoracic paraspinal malignant peripheral nerve sheath tumor (MPNST) is quite rare. Both benign and malignant nerve sheath tumors may be symptomatic, rendering clinical differentiation of limited utility. On radiographic imaging, erosion of the ribs and vertebral bodies, irregularity in contour, and inhomogeneity in attenuation are not sufficiently reliable for diagnosis of MPNST. Histologically, MPNSTs reveal hypercellularity, nuclear atypia, and mitotic activity. Surgical resection is the main modality of treatment. Postoperative radiation therapy for MPNST has led to a significant reduction in local recurrence. The prognosis is unfavorable. Herein, we present an unusual case of a posterior mediastinal mass in a 50-year-old female with delayed diagnosis of 2 years. After surgical intervention, the histologic finding was MPNST. Postoperative radiation therapy was applied because of incomplete resection. The follow-up chest computed tomography 5 months later revealed a residual soft tissue mass with significant reduction in size over the parathoracic spine area. No neurologic sequelae were identified after surgery.

Current concepts in the mediastinal lymph node staging of nonsmall cell lung cancer

OBJECTIVE

To review the current concepts in the mediastinal staging of nonsmall cell lung cancer (NSCLC), evaluating traditional and modern staging modalities.

SUMMARY BACKGROUND DATA

Staging of NSCLC includes the assessment of mediastinal lymph nodes. Traditionally, computed tomography (CT) and mediastinoscopy are used. Modern staging modalities include magnetic resonance imaging (MRI), positron emission tomography (PET), and endoscopic ultrasound with fine-needle aspiration (EUS-FNA) METHODS: Literature was searched with PubMed and SUMSearch for original, peer-reviewed, full-length articles. Studies were evaluated on inclusion criteria, sample size, and operating characteristics. Endpoints were accuracy, safety, and applicability of the staging methods.

RESULTS

CT had moderate sensitivities and specificities. With few exceptions magnetic resonance imaging (MRI) offered no advantages when compared with CT, against higher costs. PET was significantly more accurate than CT. Mediastinoscopy and its variants were widely used as gold standard, although meta-analyses were absent. Percutaneous transthoracic needle biopsy (PTNB) and transbronchial needle biopsy (TBNA) were moderately sensitive and specific. EUS-FNA had high sensitivity and specificity, is a safe and fast procedure, and is cost-effective. EUS-FNA evaluates largely a nonoverlapping mediastinal area compared with mediastinoscopy.

CONCLUSIONS

PET has the highest accuracy in the mediastinal staging of NSCLC, but is not generally used yet. EUS-FNA has the potential to perform mediastinal tissue sampling more accurate than TBNA, PTNB, and mediastinoscopy, with fewer complications and costs. Although promising, EUS-FNA is still experimental. Mediastinoscopy is still considered as gold standard for mediastinal staging of NSCLC.

State of the art in thoracospic surgery: a personal experience of 2000 videothoracoscopic procedures and an overview of the literature

BACKGROUND

Herein we compare our personal experience with a series of > 2000 videothoracoscopic procedures with those reported in the literature to identify the procedures now accepted as the gold standard, those still regarded as investigational, and those considered unacceptable.

METHODS

Between June 1991 and December 2000, we performed 2068 videothoracoscopic procedures, including lung cancer staging (n = 910), wedge resections (n = 261), lobectomies (n = 221), pneumonectomies (n = 6), the diagnosis and treatment of pleural diseases (n = 200), the treatment of pneumothorax (n = 170), giant bullae (n = 57), lung volume reduction surgery (LVRS) for emphysema (n = 41), the diagnosis and treatment of mediastinal diseases (n = 133), the treatment of esophageal diseases (n = 39), and 30 other miscellaneous procedures.

RESULTS

A review of the literature indicates that videothoracoscopy is usually considered the preferred approach for the treatment of spontaneous pneumothorax, the diagnosis of indeterminate pleural effusions, the treatment of malignant pleural effusions, sympathectomy, and the diagnosis and treatment of benign esophageal or mediastinal diseases. The videoendoscopic approach to LVRS for emphysema is still under evaluation. Videothoracoscopic wedge resections for the diagnosis of indeterminate nodules and the treatment of primary lung cancer, metastases, and other malignancies are still controversial due to oncologic concerns. Videoendoscopic major pulmonary resections are usually considered investigational or even unacceptable due to oncologic concerns, technical difficulties, and the risk of complications.

CONCLUSIONS

Although we generally agree with the foregoing recommendations, we consider videoendoscopy the best approach for LVRS and particularly useful for the staging of lung cancer, where we always perform it as the first step of the operation. We widely perform videoendoscopic major pulmonary resections, but we believe that these procedures should only be used in strictly selected cases and at specialized centers.

High resolution computed tomography and MRI for monitoring lung tumor growth in mice undergoing radioimmunotherapy: correlation with histology

A model lung tumor system has been developed in mice for the evaluation of vascular targeted radioimmunotherapy. In this model, EMT-6 mammary carcinoma tumors growing in the lung are treated with 213Bi, an alpha particle emitter, which is targeted to lung blood vessels using a monoclonal antibody. Smaller tumors (< 100 microm in diameter) are cured, but larger tumors undergo a period of regression and then regrow and ultimately prove lethal. The goal of this work was to determine if external imaging with MRI or CT could be used routinely to monitor the growth/ regression of lung tumors in live mice. To attempt to evaluate individual tumors in vivo, animals were initially imaged with magnetic resonance imaging (MRI). High resolution MRI images could be obtained only after sacrifice when lungs were not moving. In contrast, high resolution computed tomography (CT) produced evaluable images from anesthetized animals. Serial CT images (up to 5/animal) were collected over a 17 day period of tumor growth and treatment. When tumored animals became moribund, animals were sacrificed and lungs were inflated with fixative, embedded in paraffin, and then sectioned serially to compare the detection of tumors by high resolution CT with detection by histology. CT proved most useful in detecting lung tumors located in the hilar area and least useful in detecting serosal surface and anterior lobe tumor foci. Overall, CT images of live animals revealed tumors in approximately 2/3 of cases detected in histologic serial sections when relatively few tumors were present per lung. Detection of lesions and their resolution post therapy were complicated due to residual hemorrhagic, regressing tumor nodules and the development of lung edema both of which appeared as high density areas in the CT scans. We conclude that the microCT method used could identify some lung tumors as small as 100 microm in diameter; however, no concrete evaluation of therapy induced regression of the tumors could be made with CT analyses alone.

Recent advances in pulmonary imaging

Recent years have witnessed an explosion in imaging technology applicable to chest medicine. These include CT and magnetic resonance angiography (MRA) for the diagnosis of pulmonary embolism, and high-resolution CT for the detection and characterization of diffuse lung diseases and the quantification of emphysema. Newly developed approaches to pulmonary functional imaging using CT and MRI have been applied to the evaluation of pulmonary ventilation and perfusion and to the detection of small airways disease. Volumetric CT imaging techniques together with advanced image processing have made possible "virtual bronchoscopy." Positron emission tomography provides an important new approach to the accurate detection and staging of chest malignancies and to the evaluation of pulmonary nodules. Finally, new digital imaging techniques, which are rapidly replacing conventional x-ray film, offer the possibility of computer-aided diagnosis.

Is the chest radiograph a reliable tool in the assessment of tumor response after radiotherapy in nonsmall cell lung carcinoma?

BACKGROUND

The purpose of this study was to evaluate whether the chest radiograph is a reliable tool to assess response to radiotherapy.

MATERIALS AND METHODS

Pre- and post-treatment chest radiographs and computed tomographs (CT) of 63 patients with nonsmall cell lung cancer (NSCLC) treated by radiotherapy were reviewed by four observers with regard to suitability for tumor measurement, and response. Suitability for tumor measurement was expressed as the number of measurable diameters. In addition, the consequences to clinical outcome were studied by survival analysis.

RESULTS

The CT turned out to be more suited for tumor measurement before as well as after radiotherapy, resulting in an increase of the number of measurable cases. The number of measurable cases with CT was 52 (83%) as compared to 28 (44%) with chest radiography. Especially in case of centrally localized tumors, the presence of an atelectasis, or squamous cell carcinoma, CT contributed to a higher rate of measurable cases. The interobserver agreement with regard to response using chest radiograph was good (mean kappa = 0.74). In 25 of 28 cases (89%) measurable with CT as well as with chest radiograph, response was equally classified. When CT was used, the median survival of the responders was 14.2 months as compared to 6.8 months of the nonresponders. When chest radiograph was used, the median survival of these groups was 12.0 and 6.6 months respectively, which was not significantly different when response was assessed by CT.

CONCLUSION

We conclude that CT is more suited for tumor measurement because more measurable lesions can be found and more evaluable lesions on chest radiograph become measurable on CT. The chest radiograph does have a valuable role to play in those lesions that are measurable because of the good interobserver agreement with regard to the response classification, the high overall agreement between CT and chest radiograph in case of measurable cases, and the lack of important differences with regard to survival.

Radiologic imaging in cancer

Radiologic procedures are extremely valuable in the diagnostic work-up of many cancers but are limited for screening purposes to a few diseases. Radiologists have developed an extensive armamentarium of tools, from plain radiographs and nuclear-medicine scans to ultrasound, computed tomography, magnetic resonance imaging, positron emission tomography, and single-photon emission computed tomography. This article includes suggested protocols for working up the most common cancers.

Progressive mediastinal widening after therapy for Hodgkin's disease

A residual mass after treatment of Hodgkin's disease points to the diagnosis of fibrotic residue or of persistent disease. Radiological and radionuclide imaging, although helpful, cannot differentiate between both conditions with absolute certainty. Thus, residual masses are followed up: stable or regressive masses strengthen the hypothesis of fibrotic residue, while enlarging masses evoke relapsing disease. We report on a patient with an enlarging residual mass after completion of therapy, which proved to be a benign thymic hyperplasia after histological analysis. Previously reported similar observations are reviewed.