The clinical importance of magnetic resonance imaging versus computed tomography in malignant pleural mesothelioma

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.

New Updates of the Imaging Role in Diagnosis, Staging, and Response Treatment of Malignant Pleural Mesothelioma

Malignant pleural mesothelioma is a rare neoplasm with poor prognosis. CT is the first imaging technique used for diagnosis, staging, and assessment of therapy response. Although, CT has intrinsic limitations due to low soft tissue contrast and the current staging system as well as criteria for evaluating response, it does not consider the complex growth pattern of this tumor. Computer-based methods have proven their potentiality in diagnosis, staging, prognosis, and assessment of therapy response; moreover, computer-based methods can make feasible tasks like segmentation that would otherwise be impracticable. MRI, thanks to its high soft tissue contrast evaluation of contrast enhancement and through diffusion-weighted-images, could replace CT in many clinical settings.

A comparison between MRI and CT in the assessment of primary tumour volume in mesothelioma

INTRODUCTION

Primary tumour staging in Malignant Pleural Mesothelioma (MPM) using Computed Tomography (CT) imaging is confounded by perception errors reflecting low spatial resolution between tumour and adjacent structures. Augmentation using perfusion CT is constrained by radiation dosage. In this study, we evaluated an alternative tumour staging method using perfusion-tuned Magnetic Resonance Imaging (MRI).

METHODS

Consecutive patients with suspected MPM were recruited to a prospective observational study. All had MRI (T1-weighted, isotropic, contrast-enhanced 3-Tesla perfusion imaging) and CT (contrast-enhanced) pre-biopsy. Patients diagnosed with MPM underwent MRI and CT volumetry, with readers blinded to clinical data. MRI volumetry was semi-automated, using signal intensity limits from perfusion studies to grow tumour regions within a pleural volume. A similar CT method was not possible, therefore all visible tumour was manually segmented. MRI and CT volumes were compared (agreement, correlation, analysis time, reproducibility) and associations with survival examined using Cox regression.

RESULTS

58 patients were recruited and had MRI before biopsy. 31/58 were diagnosed with MPM and these scans were used for volumetry. Mean (SD) MRI and CT volumes were 370 cm3 and 302 cm3, respectively. MRI volumes were larger (average bias 61.9 cm3 (SD 116), 95 % limits (-165.5 - 289 cm3), moderately correlated with CT (r = 0.56, p = 0.002) and independently associated with survival (HR 4.03 (95 % CI 1.5-11.55), p = 0.006). CT volumes were not associated with survival, took longer to compute than MRI volumes (mean (SD) 151 (19) v 14 (2) minutes, p=<0.0001) and were less reproducible (inter-observer ICC 0.72 for CT, 0.96 for MRI).

CONCLUSIONS

MRI and CT generate different tumour volumes in MPM. In this study, MRI volumes were larger and were independently associated with survival. MRI volumetry was quicker and more reproducible than CT.

On the diagnosis of malignant pleural mesothelioma: A necropsy-based study of 171 cases (1997–2016)

Background:

Malignant pleural mesothelioma (MPM) diagnosis is known to be difficult. We report on the diagnostic elements available in life in an MPM necropsy case series and describe the frequency of non-neoplastic asbestos-related diseases as biological exposure indices.

Methods:

We reviewed pathologic and clinical records of an unselected series of autopsies (1977–2016) in patients with MPM employed in the Monfalcone shipyards or living with shipyard workers. We assessed the consistency with autopsy results of diagnoses based on, respectively, radiologic, cytologic, and histologic findings, with and without immunophenotyping.

Results:

Data on 171 cases were available: for 169, autopsy confirmed the MPM diagnosis. In life, 119 cases had histologic confirmation of diagnosis, whereas 7 were negative; all cases without immunophenotypization were autoptic MPMs. Cytology alone had been positive in 18 autoptic MPM cases, negative in 14. Radiologic imaging alone had been positive in another 16, negative in 11. In the 2 cases not confirmed at autopsy, MPM had been suspected by chest computed tomography only. Bilateral pleural plaques were found in 144 and histologic evidence of asbestosis in 62 cases.

Conclusions:

Autopsies confirmed 169/171 cases, including cases that would not be considered as certain based on diagnosis in life. Radiologic imaging, cytologic examination of pleural effusions, or both combined had low sensitivity but high positive predictive value: when they are positive, proceeding to thoracoscopy should be justified. MPM has been correctly diagnosed even without immunohistochemistry. The prevalence of pleural plaques and asbestosis was high due to severity of asbestos exposures in these cases.

Response evaluation in mesothelioma: Beyond RECIST

Malignant pleural mesothelioma (MPM) typically demonstrates a non-spherical growth pattern, so it is often difficult to accurately categorize change in tumour burden using size-based tumour response criteria (e.g., WHO (World Health Organisation), RECIST (Response Evaluation Criteria in Solid Tumours) and modified RECIST). Functional imaging techniques are applied to derive quantitative measurements of tumours, which reflect particular aspects of the tumour pathophysiology. By quantifying how these measurements change with treatment, it is possible to observe treatment effects. In this review, we survey the existing roles of CT and MRI for the management of MPM, including the currently applied size measurement criteria for the assessment of treatment response. New functional imaging techniques, such as positron emission tomography (PET), diffusion-weighted MRI (DWI) and dynamic contrast-enhanced MRI (DCE-MRI) that may potentially improve the assessment of treatment response will be highlighted and discussed.

Management of Malignant Pleural Mesothelioma

Malignant mesothelioma is increasing in incidence globally and has no known cure. Its unique clinical feature of local infiltration along tissue planes makes it a difficult neoplasm to manage. There have been few randomized controlled trials regarding treatment options, although these have increased in recent years, and results are eagerly awaited. This article summarizes important advances in the management of mesothelioma, especially diagnostic and therapeutic aspects.

Beam modeling and verification of a photon beam multisource model

Dose calculations for treatment planning of photon beam radiotherapy require a model of the beam to drive the dose calculation models. The beam shaping process involves scattering and filtering that yield radiation components which vary with collimator settings. The necessity to model these components has motivated the development of multisource beam models. We describe and evaluate clinical photon beam modeling based on multisource models, including lateral beam quality variations. The evaluation is based on user data for a pencil kernel algorithm and a point kernel algorithm (collapsed cone) used in the clinical treatment planning systems Helax-TMS and Nucletron-Oncentra. The pencil kernel implementations treat the beam spectrum as lateral invariant while the collapsed cone involves off axis softening of the spectrum. Both algorithms include modeling of head scatter components. The parameters of the beam model are derived from measured beam data in a semiautomatic process called RDH (radiation data handling) that, in sequential steps, minimizes the deviations in calculated dose versus the measured data. The RDH procedure is reviewed and the results of processing data from a large number of treatment units are analyzed for the two dose calculation algorithms. The results for both algorithms are similar, with slightly better results for the collapsed cone implementations. For open beams, 87% of the machines have maximum errors less than 2.5%. For wedged beams the errors were found to increase with increasing wedge angle. Internal, motorized wedges did yield slightly larger errors than external wedges. These results reflect the increased complexity, both experimentally and computationally, when wedges are used compared to open beams.

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.

The use of magnetic resonance imaging in malignant mesothelioma

Magnetic resonance imaging (MRI) is not routinely used in investigations for patients with suspected malignant pleural mesothelioma but it can be a useful tool in some instances--particularly predicting malignancy in patients with asbestos exposure; differentiating between metastatic pleural disease and malignant pleural mesothelioma (MPM); assessing patients for radical surgery and post treatment evaluation of patients.

CT slice index and thickness: impact on organ contouring in radiation treatment planning for prostate cancer

Objective: To assess the impact of CT slice index and thickness (3 mm versus 5 mm) on (i) prostate volume, dimensions, and isocenter coordinates, (ii) bladder and rectal volumes, and (iii) DRR quality, in the treatment of prostate cancer. Methods: 16 patients with prostate cancer underwent two planning CT‐scans using 3 and 5 mm slice index/thickness. Prostate, bladder, and rectum were outlined on all scans. Prostate isocenter coordinates, maximum dimensions, and volumes were compared along with bladder and rectal volumes. Bladder volumes and maximum diameters were further investigated using a second observer. A comparative analysis of DRR quality was conducted as well as a dosimetric analysis using DVH. Results: The differences in measurements of prostate volume, isocenter coordinates and maximum dimensions between the 3 and 5 mm scans, were small and not statistically significant. Similar finding was seen for rectal volume. However, bladder volume was always larger on the 3 mm scan (mean difference=27.9 cc;  SE=4.8 cc;  95% CI:  17.7−38.2 cc;  p<0.001) and the findings were reproduced with the second observer (mean difference=31.9 cc;  SE=4.7 cc;  95% CI:  21.9−41.9 cc;  p<0.001). The differences in volume are caused by a slight increase in (1) the measurement of the longitudinal dimensions on the 3 mm scans, and (2) the slice by slice measured bladder area on the 3 mm scans. The latter is due to partial volume effect. The 3 mm DRR were slightly better than the 5 mm DRR. The bladder DVH differed significantly in some patients. Conclusion: Bladder volume is significantly larger on the 3 mm scans. Differences in contoured areas may be accounted for, in part, by the partial volume effect.

PACS number(s): 87.57.–s, 87.53.–j

The value of chest computer tomography and cervical mediastinoscopy in the preoperative assessment of patients with malignant pleural mesothelioma

BACKGROUND

Patients with localized malignant pleural mesothelioma (MPM) can be considered for surgical resection with or without additional treatment. For this approach it is imperative to select patients without mediastinal lymph node involvement. In this study cervical mediastinoscopy (CM) is compared with computer tomography (CT) scanning for its diagnostic accuracy in assessing mediastinal lymph nodes during preoperative workup.

METHODS

Computer tomography scans of the chest and CM were performed in 43 patients with proven unilateral MPM. The CT scans were reviewed by one radiologist and two chest physicians. At CM the lymph node samples were taken from stations Naruke 2, 3, 4, and 7. Computer tomography and CM results were compared with final histopathologic findings obtained at thoracotomy or, if this was not performed, at CM.

RESULTS

Computer tomography scanning revealed pathologic enlarged lymph nodes with a shortest diameter of at least 10 mm in 17 of 43 patients (39%). There was histopathologic evidence of lymph node metastases at CM in 11 of these patients (26%). This resulted in a sensitivity of 60% and 80%, a specificity of 71% and 100%, and a diagnostic accuracy of 67% and 93% for CT and CM, respectively.

CONCLUSIONS

Cervical mediastinoscopy is a valuable diagnostic procedure for patients with MPM who are considered candidates for surgical-based therapy. Results of CM are more reliable than those obtained by CT scanning. Our data confirm results of previous studies reporting that mediastinal lymph node involvement is a frequent event in MPM.

Occupational and environmental thoracic malignancies

Lung cancer is the most common thoracic malignancy caused by exposures at work and in the environment. The most unique thoracic malignancy is mesothelioma, because it is relatively rare and one of only a few neoplasms for which one specific inciting agent-asbestos-has been identified. Based on epidemiologic studies, approximately 15% of lung cancers in men and 5% of lung cancers in women are caused by occupational exposures. The International Agency for Research on Cancer has devised a rating system by which, based on animal and human data, they assign an agent, mixture, or exposure circumstance to one of five categories, ranging from group 1 (agent is carcinogenic to humans) to group 4 (agent is probably not carcinogenic to humans). Group 1 pulmonary carcinogens reviewed in this article include arsenic, asbestos, beryllium, bis (chloromethyl) ether, cadmium, chromium (IV), mustard gas, nickel, radon, and silica. The clinical presentation and pathology of lung cancers and mesothelioma caused by such exposures do not differ from those of cancers caused by other factors. The key to the recognition of a thoracic malignancy caused by workplace or environmental exposures is clinical suspicion and consideration of all causes for the disease present. Recognition of an exposure-related case of lung cancer or mesothelioma can aid in the identification of excess risk for a whole workforce or community and can lead to actions to reduce exposure, thus preventing future cases. In addition, such recognition allows the individuals struck by devastating illness to exercise their legal rights to compensation if so desired.

Malignant pleural mesothelioma: a phase II trial with docetaxel

Current cytotoxic therapy has been of limited benefit to patients with malignant pleural mesothelioma. Single agent chemotherapy has been extensively evaluated in small series of phase II clinical trials, with disappointing responses. Docetaxel, an effective taxane in the treatment of advanced breast cancer and non-small-cell lung cancer, was administered intravenously at a dose of 100 mg/m2 every 3 weeks to 30 chemotherapy naive patients with malignant pleural mesothelioma in a prospective multi-institutional phase II clinical trial. An objective response rate (partial responses) of 10% was documented. Additionally, 21% of the patients had minor responses (intention-to-treat analysis). Three patients died within 2 weeks post-first cycle of therapy, although only one patient's death was directly attributed to the investigational drug, whilst in the majority of the patients, manageable and treatable toxicities were encountered. In this phase II clinical trial, docetaxel proved to be mildly effective in the treatment of patients with malignant pleural mesothelioma.

Intraoperative photodynamic therapy after pleuropneumonectomy in patients with malignant pleural mesothelioma: dose finding and toxicity results

OBJECTIVE

To determine the optimal administered dose of meta-tetrahydroxyphenylchlorin (mTHPC) for intraoperative photodynamic therapy (IPDT) in resected malignant pleural mesothelioma (MPM). The primary objective of this combination treatment was to improve local tumor control.

DESIGN

Phase I/II dose escalation study.

SETTING

Two Dutch cancer centers.

PATIENTS

The study included 28 patients (2 women, 26 men), with pathologically confirmed MPM. The mean age was 57 years (age range, 37 to 68 years), and the World Health Organization performance score was 0 to 1. Epithelial mesotheliomas were found in 17 patients, a sarcomatous mesothelioma was found in 1 patient, and mixed epithelial sarcomatous mesotheliomas were found in 10 patients.

METHODS

Patients were injected with 0.075 mg/kg (4 patients), 0.10 mg/kg (19 patients), or 0.15 mg/kg (5 patients) mTHPC 4 or 6 days before undergoing surgery and IPDT. Complete surgical resection (i.e., pleuropneumonectomy) was followed by integral illumination with monochromatic light of 652 nm (10 J/cm(2)). The real-time fluence rate measurements were performed using four isotropic detectors in the chest cavity to calculate the total light dose.

RESULTS

Dose-limiting toxicity was reached at the level of 0.15 mg/kg mTHPC. Three patients died in the perioperative period, and one death was directly related to photodynamic therapy. Real-time dosimetry identified 12 patients in whom additional illumination had to be given to the diaphragmatic sinuses, which were unavoidably shielded during integral illumination. In two patients, illumination was cancelled due to the insufficient resectability of the tumor. The median survival time for all 28 patients was 10 months. Local tumor control, 9 months after treatment, was achieved in 13 of the 26 patients treated with IPDT.

CONCLUSION

IPDT using mTHPC, combined with a pleuropneumonectomy, resulted in local control of disease in 50% of the treated cases. The considerable toxicity associated with the procedure, however, precludes its recommendation for widespread use. Stricter patient selection and improvements of the IPDT technique may reduce the toxicity.

Docetaxel and irinotecan (CPT-11) in the treatment of malignant pleural mesothelioma--a feasibility study

We chose to treat malignant pleural mesothelioma with a combination of docetaxel and irinotecan (CPT-11), because there have been preliminary reports that CPT-11 is active against mesothelioma, and docetaxel and CPT-11 were the most active agents in our in vitro experiments in human mesothelioma cell lines. Fifteen previously untreated patients with pleural mesothelioma (IMIG Stage III-IV) were given docetaxel 60 mg/m2 followed by CPT-11 190 mg/m2 on day 1, repeated every 3 weeks. All the patients were evaluable for toxicity and 13 patients were evaluated for response. No objective responses (complete or partial) were achieved, but there were two minor responses (overall response rate 15%) each of a duration of 4 months. Three patients had stable disease (23%); median time to progression was 7 months. Median survival in all the patients was 8.5 months from the first chemotherapy cycle and 11 months from diagnosis. Toxicity was severe with seven of 15 patients suffering neutropenic fever and six of 15 patients grade 3-4 diarrhea. The trial was discontinued because of toxicity and lack of activity. We do not recommend the combination of docetaxel and CPT-11 using the schedule presented here for further investigation in malignant mesothelioma. However, CPT-11 and docetaxel, individually, still warrant further study in this disease, especially in combination with cisplatin.