Evaluation of the clinical TNM staging system for malignant pleural mesothelioma: an assessment in 88 patients

The International Association for the Study of Lung Cancer Pleural Mesothelioma Staging Project: Expanded Database to Inform Revisions in the Ninth Edition of the TNM Classification of Pleural Mesothelioma

The International Association for the Study of Lung Cancer collaborated with the International Mesothelioma Interest Group to propose the first TNM stage classification system for diffuse pleural mesothelioma in 1995, accepted by the Union for International Cancer Control and the American Joint Committee on Cancer for the sixth and seventh edition stage classification manuals. The International Association for the Study of Lung Cancer Staging and Prognostic Factors Committee Mesothelioma Domain developed and analyzed an international registry of patients with pleural mesothelioma and updated TNM descriptors for the eighth edition of the stage classification system. To inform revisions for the forthcoming ninth edition of the TNM stage classification system, data submission was solicited for patients diagnosed between 2013 and 2022 with expanded data elements on the basis of the first project's exploratory analyses, including pleural thickness measurements, updated surgical nomenclature, and molecular markers. The resulting database consisted of a total of 3598 analyzable cases from Europe, Australia, Asia, North America, and South America, with a median age of 71 years (range: 18-99 y), 2775 (77.1%) of whom were men. With only 1310 patients (36.4%) undergoing curative-intent operations, this iteration of the database includes far more patients treated nonsurgically compared with prior. Four separate manuscripts on T, N, M, and stage groupings submitted to this journal will summarize analyses of these data and will serve collectively as the primary source of the proposed changes to the upcoming ninth edition of the pleural mesothelioma stage classification system.

The Staging of Malignant Pleural Mesothelioma

Staging of malignant pleural mesothelioma has been challenging because of a paucity of cases and poor survival. At least 5 staging systems were proposed before 1990 until the first consensus system was published in 1995. This system used tumor, node, metastasis designations and borrowed heavily from parenchymal lung cancer descriptors. With the establishment of a database to collect cases from 1995 to 2013, evidence-based revisions to the 1995 staging classification were published in 2016. With improving imaging technology, clinical staging will become more refined and, it is hoped, more useful for prognostication even without operative resection.

The IASLC Mesothelioma Staging Project: Improving Staging of a Rare Disease Through International Participation

For nearly 40 years, there was no generally accepted staging system for malignant pleural mesothelioma. In 1994, members of the International Mesothelioma Interest Group, in collaboration with the International Association for the Study of Lung Cancer, proposed a TNM staging system based on analyses of outcomes in retrospective surgical series and small clinical trials. Subsequently accepted by the American Joint Commission on Cancer and the Union for International Cancer Control for the sixth editions of their staging manuals, this system has since been the international staging standard. However, it has significant limitations, particularly with respect to clinical staging and to the categories for lymph node staging. Here we provide an overview of the development of the International Association for the Study of Lung Cancer malignant pleural mesothelioma staging database, which was designed to address these limitations through the development of a large international data set. Analyses of this database, described in papers linked to this overview, are being used to inform revisions in the eighth editions of the American Joint Commission on Cancer and Union for International Cancer Control staging systems.

Recent advances in mesothelioma staging

Lack of a consensus staging system for malignant pleural mesothelioma has had a profound impact on clinical practice and research, which necessarily relies on comparison of outcomes across multiple institutions and studies for reliable prognostic information. Some lack of agreement arises from the difficulty of conforming this particular cancer to existing staging systems because of its unique biology. The heterogeneous prognosis of patients with differing tumor histology and constant search for new more effective therapies also play a role. Periodic data-driven refinement of staging criteria, based on careful pathologic analysis of histologically homogeneous cohorts, is mandated to provide clinicians with the optimal ability to stratify patients according to survival and select treatments most appropriate for the patient's individual tumor biology.

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.

Staging and response to therapy of malignant pleural mesothelioma

Earlier staging systems tended to concentrate on advanced malignant pleural mesothelioma (MPM) and considerable variation arose among the different systems. This was addressed in 1997 when the International Mesothelioma Interest Group (IMIG) staging system was approved. This is not a perfect system as many of the distinctions it makes cannot be identified by current computed tomography (CT) and magnetic resonance imaging (MRI) scanning. However presurgical staging using CT and MRI can be useful in delineating the extent and volume of disease and in detecting unexpected advanced disease as well as alerting clinicians to the possibility of early stage malignant pleural mesothelioma. Patients response to therapy can be measured using the response evaluation criteria in solid tumors (RECIST) criteria involving multiple measurements of a single diameter of tumour thickness.

Prognostic factors in malignant mesothelioma

Many prognostic factors have been described in malignant mesothelioma, but only a limited number has been validated by prospective, confirmatory studies. These include performance status, histology, weight loss and leucocyte count. Their value as predictors of patient survival in malignant mesothelioma is limited, as is their role in current clinical practice. At this moment their main importance is their application in clinical studies, which allows a better delineation of the patient group to which the study results can be applied to and a more accurate comparison between different studies. The biological prognostic factors need confirmation by larger prospective trials and should be analysed with respect to the existing prognostic factors. In the future, their use might not be limited to the prediction of the patient survival but direct the development of new therapies and extend to the molecular prediction of tumour response.

Malignant pleural mesothelioma: evaluation with CT, MR imaging, and PET

Imaging plays an essential role in the evaluation of malignant pleural mesothelioma (MPM). Computed tomography is the primary imaging modality used for the diagnosis and staging of MPM. Magnetic resonance (MR) imaging and, more recently, positron emission tomography (PET) have emerged as modalities that can provide additional important diagnostic and prognostic information to help further delineate the extent of disease, especially in surgical candidates. Use of MR imaging performed with different pulse sequences and gadolinium-based contrast material can improve the detection of tumor extension, especially to the chest wall and diaphragm. PET can provide both anatomic and metabolic information, especially in cases of extrathoracic and mediastinal nodal metastasis. Each imaging modality has its advantages and limitations, but their combined use is crucial in determining the most appropriate treatment options for patients with MPM.

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.

Important prognostic factors in patients with malignant pleural mesothelioma, managed surgically

BACKGROUND

The factors influencing outcome after resection of malignant pleural mesothelioma (MPM) are controversial. This analysis of a prospective surgical database identifies important prognostic factors.

METHODS

Tumors were staged by the International Mesothelioma Interest Group staging system, and patients were followed until death. Prognostic factors were analyzed by log rank and Cox regression, and were considered significant if p was less than 0.05.

RESULTS

From Oct 1983 to May 1998, 231 patients underwent thoracotomy, 115 had extrapleural pneumonectomy (EPP), and 59 pleurectomy/decortication (P/D). Among patients having EPP or P/D, 142 received adjuvant therapy. The median survival for stage I tumors was 29.9 months, for stage II 19 months, for stage III 10.4 months, and for stage IV 8 months. By multivariate analysis, stage, histology, gender, adjuvant therapy, but not the type of surgical resection, were significant.

CONCLUSIONS

The better survival previously reported for P/D compared with EPP is not seen in a large database with long follow-up. Stages I and II have better survival rates than generally assumed for MPM. Locally advanced T and N status, and nonepithelial histology, identify poor prognosis patients who should be considered for novel treatment regimens.

Malignant mesothelioma presenting as pulmonary metastasis ahead of growth of primary tumour

A 59-year-old woman was admitted to Houju Memorial Hospital, Ishikawa, Japan, because of cough and fever on 30 March 1997. A diagnosis of pneumonia was made and she was given antibiotics. Her symptoms improved but failed to resolve completely on antibiotic therapy. On 9 September 1997, she revisited the hospital because of bodyweight loss and malaise. There was no history of exposure to asbestos. The chest roentgenogram revealed infiltrative shadows with vague and indistinct margins suggesting inflammatory processes, which were more extensive than those investigated on her last visit. One month later, a giant tumour was detected rapidly growing from the mediastinum and open biopsy was performed. The histological examination confirmed that the tumour was a malignant mesothelioma and the intrapulmonary nodules were its metastases. This is a rare case of pulmonary metastasis being present for several months before an appearance of primary mesothelioma.

A proposed new international TNM staging system for malignant pleural mesothelioma. From the International Mesothelioma Interest Group

STUDY OBJECTIVE

Investigation of the behavior and treatment of the diffuse malignant pleural mesothelioma (MPM) is hindered by the lack of an accurate universally accepted staging system. To address this problem, the International Mesothelioma Interest Group (IMIG) has developed a new TNM-based staging system.

METHODS

The staging system was developed at a consensus meeting of IMIG members involved in clinical research in MPM, including the originators of previously proposed staging systems. The new staging system is based on the analysis of emerging information about the impact of T and N status on survival.

RESULTS

In contrast to five previous staging systems, the T descriptors designated as T1, T2, T3, and T4, provide precise anatomic definitions of the local extent of the primary tumor. The N descriptors, designated as N0, N1, N2, and N3, are virtually identical to those used in the International Lung Cancer Staging System. The stage groupings recognize new data about the better prognosis of T1 and N0 tumors and classify those tumors into stages I and II. The adverse impact of nodal metastases on survival noted in some recent surgical series warrants placing node-positive tumors in stage III. Locally advanced unresectable (T4) tumors and extrathoracic disease (N3 or M1) are classified as stage IV.

CONCLUSION

This proposed staging system reconciles and updates several earlier systems, and can provide the framework for analyzing the results of prospective clinical trials aimed at improving the currently dismal prognosis of MPM.