The role of imaging in malignant pleural mesothelioma

Pictorial Review of Pleural Disease: Multimodality Imaging and Differential Diagnosis

The pleura is a thin, smooth, soft-tissue structure that lines the pleural cavity and separates the lungs from the chest wall, consisting of the visceral and parietal pleurae and physiologic pleural fluid. There is a broad spectrum of normal variations and abnormalities in the pleura, including pneumothorax, pleural effusion, and pleural thickening. Pneumothorax is associated with pulmonary diseases and is caused by iatrogenic or traumatic factors. Chest radiography and US help detect pneumothorax with various signs, and CT can also help assess the causes. Pleural effusion occurs in a wide spectrum of diseases, such as heart failure, cirrhosis, asbestos-related diseases, infections, chylothorax, and malignancies. Chest US allows detection of a small pleural effusion and evaluation of echogenicity or septa in pleural effusion. Pleural thickening may manifest as unilateral or bilateral and as focal, multifocal, or diffuse. Various diseases can demonstrate pleural thickening, such as asbestos-related diseases, neoplasms, and systemic diseases. CT, MRI, and fluorodeoxyglucose (FDG) PET/CT can help differentiate between benign and malignant lesions. Knowledge of these features can aid radiologists in suggesting diagnoses and recommending further examinations with other imaging modalities. The authors provide a comprehensive review of the clinical and multimodality imaging findings of pleural diseases and their differential diagnoses. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Pleural Neoplasms-What Could MRI Change?

The primary pleural neoplasms constitute around 10% of the pleural tumors. The currently recommended method for their imaging is CT which has been shown to have certain limitations. Strong development of the MRI within the last two decades has provided us with a number of sequences that could potentially be superior to CT when it comes to the pleural malignancies' detection and characterization. This literature review discusses the possible applications of the MRI as a diagnostic tool in patients with pleural neoplasms. Although selected MRI techniques have been shown to have a number of advantages over CT, further research is required in order to confirm the obtained results, broaden our knowledge on the topic, and pinpoint the sequences most optimal for pleural imaging, as well as the best methods for reading and analysis of the obtained data.

Old Borders and New Horizons in Multimodality Imaging of Malignant Pleural Mesothelioma

BACKGROUND

The purpose of this article is to describe the various imaging techniques involved in detection, staging, and preoperative planning in malignant pleural mesothelioma (MPM) focusing on new imaging modalities.

METHODS

For this purpose, first a brief summary of the etiology of MPM is given. Second, not only the commonly known, but also novel imaging modalities used in MPM will be discussed.

RESULTS

A wide range of imaging methods, from conventional chest radiography, through computed tomography and hybrid imaging to radiomics and artificial intelligence, can be used to evaluate MPM.

CONCLUSION

Nowadays multimodality imaging is considered the cornerstone in MPM diagnosis and staging.

New Era for Malignant Pleural Mesothelioma: Updates on Therapeutic Options

Malignant pleural mesothelioma (MPM) is a rare malignancy with few treatment options. Recent advances have led to US Food and Drug Administration approvals and changes in the standard of care with a novel biomedical device approved for use with platinum-pemetrexed, and also for immunotherapy agents to be included as a frontline treatment option in unresectable disease. Although predictive biomarkers for systemic therapy are not currently in use in clinical practice, it is essential to correctly identify the MPM histology to determine an optimal treatment plan. Patients with nonepithelioid MPM may have a greater magnitude of benefit to dual immunotherapy checkpoint inhibitors and this regimen should be preferred in the frontline setting for these patients. However, all patients with MPM can derive benefit from immunotherapy treatments, and these agents should ultimately be used at some point during their treatment journey. There are ongoing studies in the frontline unresectable setting that may further define the frontline therapy space, but a critical area of research will need to focus on the immunotherapy refractory population. This review article will describe the new developments in the areas of biology with genomics and chromothripsis, and also focus on updates in treatment strategies in radiology, surgery, radiation, and medical oncology with cellular therapies. These recent innovations are generating momentum to find better therapies for this disease.

Radiologic Considerations and Standardization of Malignant Pleural Mesothelioma Imaging Within Clinical Trials: Consensus Statement from the NCI Thoracic Malignancy Steering Committee - International Association for the Study of Lung Cancer - Mesothelioma Applied Research Foundation Clinical Trials Planning Meeting

Detailed guidelines pertaining to radiological assessment of malignant pleural mesothelioma are currently lacking due to the rarity of the disease, complex morphology, propensity to invade multiple planes simultaneously, and lack of specific recommendations within the radiology community about assessment, reporting, and follow-up. In March 2017, a multidisciplinary meeting of mesothelioma experts was co-sponsored by the National Cancer Institute Thoracic Malignancy Steering Committee, International Association for the Study of Lung Cancer, and the Mesothelioma Applied Research Foundation. One of the outcomes of this conference was the foundation of detailed, multidisciplinary consensus imaging and management guidelines. Here, we present the recommendations for radiologic assessment of malignant pleural mesothelioma in the setting of clinical trial enrollment. We discuss optimization of imaging parameters across modalities, standardized reporting, and response assessment within clinical trials.

Volumetric assessment in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a highly malignant pleural neoplasm with a dismal prognosis. Multimodality approach including surgery and chemotherapy are utilized to treat patients with resectable disease. Clinical staging allows for selection of patients for treatment strategies, but has not been found to be prognostic and is plagued by high interobserver variability. Tumor volume measurement on cross-sectional imaging has emerged as a potential quantitative tool with prognostic significance. This review focuses on volumetric assessment from cross-sectional imaging (CT, MRI, ¹⁸F-FDG PET/CT) and the potential prognostic benefit and applications.

Three-dimensional stereoscopic volume rendering of malignant pleural mesothelioma

Our objective was to investigate the application of three-dimensional (3D) stereoscopic volume rendering with perceptual colorization on preoperative imaging for malignant pleural mesothelioma. At present, we have prospectively enrolled 6 patients being considered for resection of malignant pleural mesothelioma that have undergone a multidetector-row computed tomography (CT) scan of the chest. The CT data sets were volume rendered without preprocessing. The resultant 3D rendering was displayed stereoscopically and used to provide information regarding tumor extent, morphology, and anatomic involvement. To demonstrate this technique, this information was compared with the corresponding two-dimensional CT grayscale axial images from two of these patients. Three-dimensional stereoscopic reconstructions of the CT data sets provided detailed information regarding the local extent of tumor that could be used for preoperative surgical planning. Three-dimensional stereoscopic volume rendering for malignant pleural mesothelioma is a novel approach. Combined with our innovative perceptual colorization algorithm, stereoscopic volumetric analysis potentially allows for the accurate determination of the extent of pleural mesothelioma with results difficult to duplicate using grayscale, multiplanar CT images.

Orthotopic pleural mesothelioma in mice: SPECT/CT and MR imaging with HER1- and HER2-targeted radiolabeled antibodies

PURPOSE

To evaluate the potential of anti-human epidermal growth factor receptor (HER)1- and anti-HER2-targeted radiolabeled antibodies and magnetic resonance (MR) imaging for imaging of orthotopic malignant pleural mesothelioma (MPM) in mouse models.

MATERIALS AND METHODS

Animal studies with 165 mice were performed in accordance with National Institutes of Health guidelines for the humane use of animals, and all procedures were approved by the institutional Animal Care and Use Committee. Flow cytometry studies were performed to evaluate HER1 and HER2 expression in NCI-H226 and MSTO-211H mesothelioma cells. Biodistribution and single photon emission computed tomography (SPECT)/computed tomography (CT) imaging studies were performed in mice (four or five per group, depending on tumor growth) bearing subcutaneous and orthotopic MPM tumors by using HER1- and HER2-targeted indium 111 ((111)In)- and iodine 125 ((125)I)-labeled panitumumab and trastuzumab, respectively. Longitudinal MR imaging over 5 weeks was performed in three mice bearing orthotopic tumors to monitor tumor growth and metastases. SPECT/CT/MR imaging studies were performed at the final time point in the orthotopic models (n = 3). The standard unpaired Student t test was used to compare groups.

RESULTS

Orthotopic tumors and pleural effusions were clearly visualized at MR imaging 3 weeks after tumor cell inoculation. At 2 days after injection, the mean (111)In-panitumumab uptake of 29.6% injected dose (ID) per gram ± 2.2 (standard error of the mean) was significantly greater than the (111)In-trastuzumab uptake of 13.6% ID/g ± 1.0 and the (125)I-panitumumab uptake of 7.4% ID/g ± 1.2 (P = .0006 and P = .0001, respectively). MR imaging fusion with SPECT/CT provided more accurate information about (111)In-panitumumab localization in the tumor, as the tumor was poorly visualized at CT alone.

CONCLUSION

This study demonstrates the utility of radiolabeled anti-HER1 antibodies in the imaging of MPM in preclinical models.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12121021/-/DC1.

Clinical consequences of asbestos-related diffuse pleural thickening: A review

Asbestos-related diffuse pleural thickening (DPT), or extensive fibrosis of the visceral pleura secondary to asbestos exposure, is increasingly common due to the large number of workers previously exposed to asbestos. It may coexist with asbestos related pleural plaques but has a distinctly different pathology. The pathogenesis of this condition as distinct from pleural plaques is gradually becoming understood. Generation of reactive oxygen and nitrogen species, profibrotic cytokines and growth factors in response to asbestos is likely to play a role in the formation of a fibrinous intrapleural matrix. Benign asbestos related pleural effusions commonly antedate the development of diffuse pleural thickening. Environmental as well as occupational exposure to asbestos may also result in pleural fibrosis, particularly in geographic areas with naturally occurring asbestiform soil minerals. Pleural disorders may also occur after household exposure. High resolution computed tomography (CT) is more sensitive and specific than chest radiography for the diagnosis of diffuse pleural thickening, and several classification systems for asbestos-related disorders have been devised. Magnetic resonance imaging and fluorodeoxyglucose positron emission tomography (PET) scanning may be useful in distinguishing between DPT and malignant mesothelioma. DPT may be associated with symptoms such as dyspnoea and chest pain. It causes a restrictive defect on lung function and may rarely result in respiratory failure and death. Treatment is primarily supportive.

Local recurrence of tumor at sites of intervention in malignant pleural mesothelioma

In malignant pleural mesothelioma (MPM) patients, local dissemination (LD) of the tumor is frequently observed at the sites of intervention where diagnosis/treatment are performed. We evaluate the factors affecting LD frequency and discuss the use of PR in MPM patients. Histopathologically diagnosed 212 MPM patients who had not received PR were evaluated in terms of development of LD. Of the 212 patients, 29 received supportive therapy, 157 received chemotherapy and 26 received multi-modal therapy. The LD frequency was 13.2% for all patients. The median survival rate was 9 or 10 months in patients with or without LD, respectively. A higher LD frequency was observed in patients receiving thoracotomy. The LD appearance time in supportive care is short. The LD frequency in patients treated with chemotherapy that revealed progressive disease was higher than the patients who revealed stable disease or objective response. LD developed in 2 months in patients with sarcomatous and mixed cell type, and the survival rate was low. LD was not associated with the stage of the disease. The most suitable candidate groups for PR are patients receiving supportive therapy, thoracotomy without multi-modal therapy or patients with sarcomatous and mixed cell type tumors.

Current state and future directions of pleural mesothelioma imaging

The diagnosis, staging, and response assessment of mesothelioma pose unique challenges to radiologic imaging. No single, conventional imaging approach captures the information necessary to direct all aspects of patient management. Instead, the complexities of this unique disease demand the integration of elements cleverly adapted from different modalities. Imaging-based studies presented at the 8th International Conference of the International Mesothelioma Interest Group (IMIG) in October 2006 sought to further define the current practice and future potential of radiology for the mesothelioma patient. The imaging studies selected through a peer-review process for presentation at the 2006 IMIG Conference were intended to frame this research in the context of the unique imaging challenges presented by mesothelioma while stimulating dialogue on the future resolution of these challenges. This communication conveys the pitfalls and potential of pleural mesothelioma imaging based on work presented at the Conference. From diagnosis to response, PET/CT to molecular bioprobes, volumetric analysis to computerized tumor assessment, imaging promises to provide valuable insight for patients with mesothelioma and the physicians who treat them.

Assessment of tumor response in malignant pleural mesothelioma

Most patients with malignant pleural mesothelioma (MPM) are candidates for chemotherapy during the course of their disease. Assessment of the response with conventional criteria based on computed tomography (CT) measurements is challenging, due to the circumferential and axial pattern of growth of MPM. Such difficulties hinder an accurate evaluation of clinical study results and make the clinical management of patients critical. Several radiological response systems have been proposed, but neither WHO criteria nor the more recent RECIST unidimensional criteria nor hybrid uni- and bidimensional criteria seem to apply to tumor measurement in this disease. Recently, modified RECIST criteria for MPM have been published. Although they are already being used in current clinical trials, they have been criticized based on the high grade of inter-observer variability and on theoretical studies of mesothelioma growth according to non-spherical models. Computer-assisted techniques for CT measurement are being developed. The use of FDG-PET for prediction of response and, more importantly, of survival outcomes of MPM patients is promising and warrants validation in large prospective series. New serum markers such as osteopontin and mesothelin-related proteins are under evaluation and in the future might play a role in assessing the response of MPM to treatment.

Pleural Mesothelioma: Sensitivity and Incidence of Needle Track Seeding after Image-guided Biopsy versus Surgical Biopsy

PURPOSE

To retrospectively compare the sensitivity of image-guided core-needle biopsy, thoracoscopy, and thoracotomy in the diagnosis of malignant pleural mesothelioma and to retrospectively determine the incidence of needle track seeding after these procedures.

MATERIALS AND METHODS

Institutional review board approval was obtained, and informed consent was not required. The study included 100 consecutive patients (81 men, 19 women; average age, 65.8 years) with pathologically proved malignant pleural mesothelioma who were treated between 1994 and 2002. A total of 23 core-needle biopsies were performed in 22 patients, and 11 of these biopsies were coupled with fine-needle aspiration biopsy. A coaxial technique was used, and biopsy was performed with fluoroscopic (12 biopsies), computed tomographic (10 biopsies), or ultrasonographic (one biopsy) guidance. Sixty-nine patients underwent surgical biopsy in the form of thoracoscopy (n = 51) and/or thoracotomy (n = 21). Patients were followed up clinically for any evidence of needle track seeding after image-guided or surgical procedures. The sensitivity of diagnostic procedures and the incidence of needle track seeding as a result of intervention were calculated.

RESULTS

Sensitivity was 86% for image-guided core-needle biopsy, 94% for thoracoscopy, and 100% for thoracotomy. The incidence of needle track seeding was 4% for image-guided core-needle biopsy and 22% for surgical biopsy.

CONCLUSION

Image-guided core-needle biopsy in patients with malignant pleural mesothelioma has a lower incidence of needle track seeding than surgical biopsy and has a high sensitivity for diagnosis.

Dynamic Contrast-Enhanced MRI of Malignant Pleural Mesothelioma

STUDY OBJECTIVE

Dynamic contrast-enhanced MRI (DCE-MRI) followed by pharmacokinetic analysis has been successfully used in a variety of solid tumors. The aims of this study were to evaluate the feasibility of DCE-MRI in malignant pleural mesothelioma (MPM), to differentiate benign from pathologic tissue and compare pharmacokinetic with clinical parameters and survival in order to map out its microcirculation; and to compare pharmacokinetic with clinical parameter and survival in order to improve our understanding of the in vivo biology of this malignancy.

METHODS

Nineteen patients with a diagnosis of MPM who were scheduled to receive chemotherapy with gemcitabine were enrolled in the study. DCE-MRI was performed before treatment (n = 19) and after the third cycle (n = 12) and sixth cycle (n = 7) of chemotherapy. An established pharmacokinetic two-compartment model was used to analyze DCE-MRI. Tumor regions were characterized by the pharmacokinetic parameters amplitude (Amp), redistribution rate constant (kep), and elimination rate constant (kel). Kinetic parameters of tumor tissue and normal tissue were compared using the Student t test. Patients were classified as clinical responders or nonresponders according to clinical outcome, and these groups were compared with the pharmacokinetic parameters derived from DCE-MRI.

RESULTS

Normal and tumor tissue could be distinguished by the pharmacokinetic parameters Amp and kel (p </= 0.001). Clinical responders had a median kep value within the tumor of 2.6 min, while nonresponders showed a higher value (3.6 min), which coincided with longer survival (780 days vs 460 days).

CONCLUSIONS

DCE-MRI can be used in patients with MPM to assess tumor microvascular properties and to demonstrate tumor heterogeneity for therapy monitoring. High pretherapeutic values of kep within the tumor correlated with a poor overall response to therapy.

Variability in mesothelioma tumor response classification

OBJECTIVE

The objective of our study was to evaluate observer variability in the measurement of temporal change in mesothelioma tumor thickness and in the resulting tumor response classification from CT scans. In addition, the performance of a semiautomated measurement method was evaluated.

MATERIALS AND METHODS

Four observers individually used an interface that displayed two serial CT scans from the same patient to measure mesothelioma tumor thickness on the follow-up CT scans of 22 patients based on baseline scan measurements. During one session, observers acquired measurements on the follow-up scans based on written reports of baseline scan measurements; in another session, baseline scan measurements were superimposed on the baseline scan for direct visual comparison. Follow-up scan measurements also were obtained from a semiautomated method. Measurement variability and tumor response classification concordance were evaluated for manual measurements acquired in both modes and for semiautomated measurements.

RESULTS

Although only a small increase in tumor response classification concordance rate was obtained with the visual approach (84.8%) relative to the more standard written-report approach (82.6%), the actual measurements acquired by observers were statistically significantly different between the two approaches (p = 0.03). Both the semiautomated measurements and the resulting tumor response classifications were consistent with manual measurements.

CONCLUSION

The presentation of baseline scan tumor measurements affects measurements acquired on follow-up scans and could influence tumor response classification. The potential utility of semiautomated tumor thickness measurements was shown in the context of measuring tumor response.

Preoperative Evaluation of Patients With Malignant Pleural Mesothelioma: Role of Integrated CT-PET Imaging

Malignant pleural mesothelioma (MPM) is an uncommon neoplasm arising from mesothelial cells of the pleura. The prognosis is poor with a median survival of 8 to 18 months after diagnosis. Multimodality regimens combining chemotherapy, radiotherapy, immunotherapy, and surgery are being used more frequently in patient management. Extrapleural pneumonectomy is the surgical treatment of choice in 10% to 15% of patients who present with resectable disease and is reported to prolong survival. Accurate staging is important to distinguish patients who are resectable from those requiring palliative therapy. Integrated computed tomography-positron emission tomography (CT-PET) increases the accuracy of overall staging in patients with MPM and significantly improves the selection of patients for curative surgical resection. Specifically, CT-PET detects more extensive disease involvement than that shown by other imaging modalities and is particularly useful in identifying occult distant metastases. This article reviews aspects of imaging performed in the initial staging of patients with MPM according to the International Mesothelioma Interest Group staging system and will emphasize the appropriate role of CT-PET imaging in determining the T, N, and M descriptors.

Monitoring of Lung Motion in Patients With Malignant Pleural Mesothelioma Using Two-Dimensional and Three-Dimensional Dynamic Magnetic Resonance Imaging

PURPOSE

To monitor lung motion in patients with malignant pleural mesothelioma (MPM) before and after chemotherapy (CHT) using 2-dimensional (2D) and 3-dimensional (3D) dynamic MRI (dMRI) in comparison with spirometry.

METHODS AND MATERIALS

Twenty-two patients with MPM were examined before CHT, as well as after 3 and 6 CHT cycles (3 months and 6 months) using 2D dMRI (trueFISP; 3 images/s) and 3D dMRI (FLASH 3D, 1 slab (52 slices)/s) using parallel imaging in combination with view-sharing technique. Maximum craniocaudal lung dimensions (2D) and lung volumes (3D) were monitored, separated into the tumor-bearing and nontumor-bearing hemithorax. Vital capacity (VC) was measured for comparison using spirometry.

RESULTS

Using 2D technique, there was a significant difference between the tumor-bearing and the nontumor-bearing hemithorax before CHT (P < 0.01) and after 3 CHT cycles (P < 0.05), whereas difference was not significant in the second control. In the tumor-bearing hemithorax, mobility increased significantly from the status before versus after 3 CHT cycles (4.1 +/- 1.1 cm vs. 4.8 +/- 1.4 cm, P < 0.05). Using 3D technique, at maximum inspiration, the volume of the tumor-bearing hemithorax was 0.6 +/- 0.4 L and of the nontumor-bearing hemithorax 1.25 +/- 0.4 L before CHT. In the follow-up exams, these volumes changed to 1.05 +/- 0.4 L (P < 0.05) and 1.4 +/- 0.5 L, respectively. Using spirometry, there was no significant change in VC (1.9 +/- 0.4 L vs. 2.2 +/- 0.7 L vs. 2.2 +/- 0.9 L).

CONCLUSION

dMRI is capable of monitoring changes in lung motion and volumetry in patients with MPM not detected by global spirometry. Thus, dMRI is proposed for use as a further measure of therapy response.

Extended surgical staging for potentially resectable malignant pleural mesothelioma

BACKGROUND

Extrapleural pneumonectomy for malignant pleural mesothelioma (MPM) is a high-risk procedure, and patients require careful preoperative staging to exclude advanced disease. Computed tomography, magnetic resonance imaging, and positron emission tomography are useful staging modalities, but do not reliably identify contralateral mediastinal involvement or transdiaphragmatic invasion. We evaluated the role of extended surgical staging procedures, which generally includes a combination of laparoscopy, peritoneal lavage, and mediastinoscopy, to more precisely stage patients with MPM.

METHODS

One hundred eighteen patients with MPM, deemed clinically and radiologically resectable, underwent extended surgical staging. Mediastinoscopy was performed in 111 patients, laparoscopy in 109 patients, and peritoneal lavage in 78 patients.

RESULTS

Ten (9.2%) patients had gross evidence of transdiaphragmatic or peritoneal involvement. Peritoneal lavage was positive for metastatic MPM in 2 (2.6%) patients, neither of whom had obvious transdiaphragmatic invasion. Ipsilateral mediastinal nodes contained metastatic tumor in 10 of 62 (16.1%) patients. Contralateral nodes were positive in 4 of 111 (3.6%) patients. Of the patients who underwent biopsy of both ipsilateral and contralateral mediastinal nodes, and who had complete pathologic staging after extrapleural pneumonectomy (n = 46), 14 (30.4%) had N2-positive nodes. Only 5 of these patients were correctly identified by mediastinoscopy (sensitivity 36%, accuracy 80%). Extended surgical staging identified 16 (13.6%) patients who had contralateral nodal involvement, transdiaphragmatic invasion, or positive peritoneal cytology.

CONCLUSIONS

Extended surgical staging defines an important subset of patients with unresectable MPM not identified by imaging. Because of the potential morbidity associated with extrapleural pneumonectomy, we advocate that extended surgical staging be performed in all patients with MPM before resection.

Use of imaging in the management of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an increasingly prevalent tumour. The death rate associated with MPM is predicted to peak in the next 10 years, although radiologists and clinicians will be encountering cases for the next few decades. Contrast-enhanced CT is an established technique for evaluating suspected malignant pleural disease, but MPM can be reliably diagnosed only by histological sampling. However, even with adequate sampling and the use of immunocytochemistry, histological diagnosis is known to be difficult; definitive diagnosis may involve a combination of clinical presentation, radiological and histological appearances. Percutaneous biopsy is a promising technique for sampling the pleura. In view of its pattern of growth, MPM is a challenging disease to image by any method, and it behaves quite differently from lung cancer. This review aims to highlight the practical aspects of assessing malignant pleural mesothelioma.

Advances in the diagnosis, evaluation, and management of malignant pleural mesothelioma

Malignant mesothelioma is an insidious neoplasm arising from the mesothelial surfaces of the pleural and peritoneal cavities, the pericardium, or the tunica vaginalis. A total of 80% of all cases are pleural in origin. The predominant cause of malignant mesothelioma is inhalational exposure to asbestos, although evidence is increasing to support the hypothesis that simian virus-40 virus plays a role in cocarcinogenesis. Immunohistochemical markers such as calretinin, WT-1, and cytokeratin 5/6 are becoming established diagnostic markers. Preliminary data suggests that a soluble form of mesothelin could serve as a serum marker for established and early cases of mesothelioma. Positron emission tomography with 18-fluorodeoxyglucose in conjunction with computed tomograhy scanning has improved preoperative imaging and staging. Prognostic factors have been identified and verified. Negative indicators include thrombocytosis, high leukocyte counts, poor performance status, and nonepithelial histology. For the first time, there is now evidence that some treatments are increasing the quality and quantity of life for patients with mesothelioma. Chemotherapy, with the new multi-targeted antifolate drug Pemetrexed, combined with cisplatin, has shown superior survival rates in a large phase III trial when compared to cisplatin alone. High-dose intensity-modulated radiotherapy when administered after extrapleural pneumonectomy has resulted in excellent local control. Multimodality treatment programs that combine surgical cytoreduction with novel forms of radiation therapy and more effective chemotherapy combinations may offer significant increases in survival for certain subgroups of mesothelioma patients. Innovative palliative approaches have proved successful in alleviation of the significant symptoms experienced by many mesothelioma patients. Experimental treatments such as immunotherapy and gene therapy present a window of hope for all mesothelioma patients, and in the future, may be combined with 'standard therapy' in multimodality protocols. Patients with adequate performance status should be enrolled into clinical trials where possible. Over the past decade, significant advances have been made on several fronts that have improved the ability to diagnose a stage, define prognosis, and treat malignant pleural mesothelioma.

Evaluation of semiautomated measurements of mesothelioma tumor thickness on CT scans

RATIONALE AND OBJECTIVES

To evaluate the clinical acceptability of semiautomated methods for the measurement of mesothelioma tumor thickness in computed tomography (CT) scans.

MATERIALS AND METHODS

A computer interface was developed to allow the acquisition of semiautomated mesothelioma tumor thickness measurements, which require the manual selection of a point along the outer margin of the tumor in a CT section. After application of an automated lung segmentation method, the computer automatically identifies a corresponding point along the inner margin of the tumor (as represented by the lung boundary), constructs a line segment between the manually selected outer tumor margin point and the computer-determined inner tumor margin point, and computes tumor thickness as the length of this line segment. Three radiologists and oncologists independently reviewed line segments representing the semiautomated measurements generated by three different algorithms at 134 measurement sites in the CT scans of 22 mesothelioma patients. The observers either accepted a measurement line segment or modified it through the interface. Differences between the initial semiautomated measurements and the measurements as modified by the observers were analyzed.

RESULTS

The frequency with which observers accepted the semiautomated measurements without modification was as high as 86%. Of all measurements across all observers and methods (1,206 measurements), 89% were changed by 2 mm or less.

CONCLUSION

We have developed semiautomated methods to measure mesothelioma tumor thickness. The potential of these methods has been demonstrated through an observer study. We expect these methods to become important tools for the efficient quantification of tumor extent.

Alterações pleurais e parenquimatosas relacionadas com a exposição ao asbesto: Ensaio pictórico

Pleural and pulmonary asbestos-related diseases range from benign conditions, like pleural effusion and pleural plaques, to some neoplasias, such as lung cancer and malignant mesothelioma. Pleural effusion is the earliest finding after asbestos exposure, but the imaging findings are not specific. Diffuse pleural thickening involves the visceral pleura and pleural plaques are considered to be hallmarks of exposure. Asbestosis is the pulmonary fibrosis due to asbestos. Rounded atelectasis is a peripheral lung collapse in these individuals, generally related to pleural disease. Some neoplasias, like lung carcinoma and pleural mesothelioma, are more prevalent in asbestos-exposed subjects. The aim of this essay is to illustrate the main imaging findings of asbestos-related diseases.

Malignant mesothelioma

Malignant mesothelioma is an aggressive, treatment-resistant tumour, which is increasing in frequency throughout the world. Although the main risk factor is asbestos exposure, a virus, simian virus 40 (SV40), could have a role. Mesothelioma has an unusual molecular pathology with loss of tumour suppressor genes being the predominant pattern of lesions, especially the P16INK4A, and P14ARF, and NF2 genes, rather than the more common p53 and Rb tumour suppressor genes. Cytopathology of mesothelioma effusions or fine-needle aspirations are often sufficient to establish a diagnosis, but histopathology is also often required. Patients typically present with breathlessness and chest pain with pleural effusions. Median survival is now 12 months from diagnosis. Palliative chemotherapy is beneficial for mesothelioma patients with high performance status. The role of aggressive surgery remains controversial and growth factor receptor blockade is still unproven. Gene therapy and immunotherapy are used on an experimental basis only. Patterns identified from microarray studies could be useful for diagnosis as well as prognostication.

Fluorodeoxyglucose-PET in characterizing solitary pulmonary nodules, assessing pleural diseases, and the initial staging, restaging, therapy planning, and monitoring response of lung cancer

Fluorodeoxyglucose-PET imaging has secured an important role in the assessment and management of a multitude of pulmonary disorders, including solitary pulmonary nodules, lung cancer, and pleural diseases. While conventional imaging modalities such as chest radiography and CT are considered essential in these settings, FDG-PET can provide new information and complement structural imaging techniques in the evaluation of such disorders. In this review, the authors present a growing body of evidence that demonstrates and supports the utility of FDG-PET in the differentiation of benign and malignant pulmonary nodules, the assessment of lung cancer in various stages of disease, and the characterization of pleural diseases. In addition, new developments--such as prospects for potential utility of novel radiotracers and delayed imaging--that can further refine the role of FDG scans in the work-up of lung nodules and cancer and forecast the future place of PET in these common modalities are discussed.

Malignant pleural mesothelioma

Malignant pleural mesothelioma is an uncommon tumor; only about 3000 cases are diagnosed annually in the United States. Cases were described early in the 20th century, but their relationship to asbestos exposure was not documented until 1960. Since then, the incidence has appeared to increase, and numerous epidemiologic studies have confirmed that exposure to asbestos in a variety of settings and occupations is the most significant risk factor for the development of malignant pleural mesothelioma. More recently, the oncogenic virus SV40 has also been implicated as a potential etiologic agent. Surgery, radiotherapy, and chemotherapy have each been used in the treatment of mesothelioma, but generally with little impact on survival. New directions in therapy include aggressive multimodality programs for potentially resectable patients and targeted therapies, including antifolates, antiangiogenesis agents, and drugs directed at epidermal growth factor receptor for the majority of patients presenting with unresectable disease.

Asbestos-Related Pleural Disease

OBJECTIVES

We sought to compare respiratory-gated high-spatial resolution magnetic resonance imaging (MRI) and radial MRI with ultra-short echo times with computed tomography (CT) in the diagnosis of asbestos-related pleural disease.

METHODS

Twenty-one patients with confirmed long-term asbestos exposure were examined with a CT and a 1.5-T MR unit. High-resolution respiratory-gated T2w turbo-spin-echo (TSE), breath-hold T1w TSE, and contrast-enhanced fat-suppressed breath-hold T1w TSE images with an inplane resolution of less than 1 mm were acquired. To visualize pleural plaques with a short T2* time, a pulse sequence with radial k-space-sampling was used (TE = 0.5 milliseconds) before and after administration of Gd-DTPA. CT and MR images were assessed by 4 readers for the number and calcification of plaques, extension of pleural fibrosis, extrapleural fat, detection of mesothelioma and its infiltration into adjacent tissues, and detection of pleural effusion. Observer agreement was studied with the use of kappa statistics.

RESULTS

The MRI protocol allowed for differentiation between normal pleura and pleura with plaques. Interobserver agreement was comparable for MRI and CT in detecting pleural plaques (median kappa = 0.72 for MRI and 0.73 for CT) and significantly higher with CT than with MRI for detection of plaque calcification (median kappa 0.86 for CT and 0.72 for MRI; P = 0.03). Median sensitivity of MRI was 88% for detection of plaque calcification compared with CT. For assessment of pleural thickening, pleural effusion, and extrapleural fat, interobserver agreement with MRI was significantly higher than with CT (median kappa 0.71 and 0.23 for pleural thickening, 0.87 and 0.62 for pleural effusion, and 0.7 and 0.56 for extrapleural fat, respectively; P < 0.05). For detection of mesothelioma, median kappa was 0.63 for MRI and 0.58 for CT.

CONCLUSION

High-resolution MR sequences and radial MRI achieve a comparable interobserver agreement in detecting pleural plaques and even a higher interobserver agreement in assessing pleural thickening, pleural effusion, and extrapleural fat when compared with CT.

Malignant pleural mesothelioma--an update

Exposure to asbestos is the most frequent, but not exclusive, cause of malignant mesothelioma. Clinical features include dyspnea, cough, nonspecific chest pain, weight loss and night sweats. Diagnosis may be complicated by histologic difficulties. Thoracoscopic techniques are proving beneficial, but no one method of imaging has proven superior, and disease staging is inconsistent. Conventional treatments such as chemotherapy, surgery, and radiotherapy have had variable impacts, although chemotherapy is useful in palliation and can improve both survival and quality of life. There is hope for new antimetabolite agents. The role of radical surgery is yet to be evaluated in a large trial. New radiotherapeutic techniques to improve local control are promising. Multimodality treatments appear to be the most successful for management of potentially resectable disease. It is likely that biological markers will improve accuracy in staging and prognosis. With new treatments based on better understanding of the biology of the disease, there is cautious optimism for the future for patients with malignant pleural mesothelioma.

Positron emission tomography in the diagnosis of mesothelioma

The increasing incidence of malignant pleural mesothelioma has led to the development of new treatment strategies and a need for new diagnostic techniques to identify the extent of the disease at an early stage and to evaluate treatment. Computed tomography (CT) and magnetic resonance imaging (MRI) are helpful in identifying the location and extent of the involved areas but cannot always differentiate between benign and malignant processes. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) imaging, which in oncology, is based on changes in metabolic pathways of glucose, has been shown in a number of studies to differentiate malign and benign lesions in patients with asbestos exposure. FDG-PET images were also found to provide excellent delineation of the active tumour sites. Further evaluations of this technique included a combined experimental/clinical study to investigate the difference in rates of FDG uptake between malignant and inflammatory cells and processes.

Role of18F-FDG PET for Evaluating Malignant Pleural Mesothelioma

Malignant Pleural Mesothelioma (MPM) is a relatively rare neoplasia characterized by a poor prognosis. Recent studies show that new therapeutic approaches can lead to an improvement in life quality and to a prolonged survival; therefore, proper evaluation of MPM before, as well as after, therapy, is needed. The aim of this study was to evaluate the impact of 18F-FDG photon emission tomography (PET) scan compared to computed tomography (CT) findings in patients affected by MPM, whether untreated or already treated. We studied 15 consecutive patients (13 male and 2 female) with a histological diagnosis of MPM, with a mean age of 69.9 years (range: 38-78 years old) and a recent total-body CT scan. Five (5) patients were studied for staging, while 10 patients were studied after therapy. An FDG PET scan was carried out 60 minutes after an intravenous (i.v.) injection of 370 MBq of 18F-FDG. For each patient, we compared the PET stage to the CT stage, and evaluated the role of PET in choosing a therapeutic approach. In 9 of 15 (60%) patients, there was no difference between the PET and the CT stage. In 2 of 15 (13%) patients, PET upstaged the disease, while in 4 of 15 (27%) patients PET downstaged MPM. According to these results, patient management was changed in 3 cases. Specifically, 1 patient was excluded from surgery, and 2 patients had different chemotherapy. These data suggest that PET is useful in the evaluation of MPM, giving additional data that can clarify doubtful CT findings, especially regarding lymph node involvement and distant lesions. In conclusion, FDG PET was found to play a worth-while role in patient management.

Imaging of pleural and chest wall tumors

MPM is a difficult disease to characterize radiographically because of its diffuse nature and propensity to infiltrate between tissue planes. Although significant information is obtained by CT, MRI, and PET, correlation with intraoperative findings is inconsistent. Overall, CT and MRI are similar in predicting surgical resectability of pleural and chest wall malignancies. MRI has a slight advantage in select situations such as Pancoast tumors; however, CT is less expensive and is sufficient in the majority of cases. Because radiologic imaging cannot differentiate benign from malignant lesions with 100% accuracy, surgical biopsy remains the gold standard for diagnosis. Newer imaging modalities such as PET scan and combined PET/CT might provide greater information and warrant further study in the preoperative evaluation of pleural and chest wall tumors.

The role of new imaging techniques in diagnosis and staging of malignant pleural mesothelioma

This review highlights the different imaging modalities for the detection of malignant pleural mesothelioma. The chest film is the initial diagnostic tool of choice because it is easy to perform, inexpensive, and widely available. Unfortunately, it demonstrates malignant pleural mesothelioma in later stages of disease and is not suitable for an early sensitive and specific diagnosis. Computed tomography is capable of distinguishing the different forms of pleural abnormalities. The knowledge of computed tomography findings is important for differentiation of malignant pleural diseases from benign diseases. Contrast-enhanced magnetic resonance imaging in three planes can be clinically useful to differentiate pleural mesothelioma from other malignancies or from benign pleural diseases. Furthermore, magnetic resonance imaging offers the possibility to differentiate invasion of the diaphragm from transdiaphragmatic tumor growth, and, in patients who are surgical candidates and who have questionable areas of local tumor extension on computed tomography, magnetic resonance imaging may provide additional information to plan or avoid surgery. Improvements in the detection of regional and distant metastases are needed to identify patients most likely to benefit from aggressive combined modality treatment regimes. In this context, positron emission tomography is a metabolic imaging technique that offers the possibility to evaluate active malignant cells. Drawbacks to this technique include false-positive findings, which may occur at sides of inflammation, and lesser anatomic detail information. A complete and accurate staging of malignant pleural mesothelioma is essential to evaluate the efficacy of new therapeutic strategies. This implies the need to be familiar with the most recently developed staging system from the International Mesothelioma Interest Group.