From the Guidelines
The staging of malignant mesothelioma (MM) is primarily based on the 8th revision of the Union for International Cancer Control (UICC) TNM (tumour-node-metastasis) staging system, as outlined in the recent guidelines by the European Society for Medical Oncology (ESMO) 1. The TNM system is crucial for determining the extent of the disease, which in turn guides treatment decisions and prognosis.
- The T stage refers to the size and extent of the primary tumor, with higher numbers indicating more extensive disease.
- The N stage refers to the presence or absence of lymph node involvement, with N0 indicating no involvement, and N1, N2, and N3 indicating increasing levels of involvement, and contralateral nodes now classified as N2 1.
- The M stage refers to the presence or absence of distant metastases, with M0 indicating no metastases, and M1 indicating metastatic disease.
For malignant pleural mesothelioma (MPM), the staging system ranges from I to IV, with Stage I indicating localized disease, Stage II indicating more extensive local tumor growth, Stage III indicating locally advanced disease or lymph node involvement, and Stage IV indicating distant metastases 1.
- Accurate staging typically requires a combination of imaging studies, including contrast-enhanced CT scans of the thorax and upper abdomen, as well as additional investigations such as endobronchial ultrasound (EBUS) or mediastinoscopy for surgical candidates, and positron emission tomography (PET)-CT to exclude occult distant metastatic disease 1.
- The choice of imaging modalities and staging investigations depends on the individual patient's disease characteristics and treatment plans, with the goal of obtaining accurate staging information to guide treatment decisions and improve outcomes.
From the Research
Stages of Malignant Mesothelioma (MM)
The stages of malignant mesothelioma (MM) are typically classified using the TNM-staging system, which takes into account the extension of the tumor (T), number of nodes (N), and presence of metastases (M) 2. The current TNM-staging system (7th edition) enables clinicians to either clinically or pathologically stage the severity of the disease.
TNM-Staging System
The TNM-staging system is used to classify MM into four stages:
- Stage I-III: Patients with these stages are considered for surgery 2
- Stage IV: Patients with this stage are indicated for palliative treatment 2
Limitations of the TNM-Staging System
Despite its widespread use, the validity of the TNM-staging system is questioned due to the low prevalence, histological variety, and retrospective nature of previous study designs 2. The International Association for the Study of Lung Cancer (IASLC) has initiated the "Mesothelioma Staging Project" to address these limitations and optimize the staging system 2.
Prognostic Factors
Prognostic factors, such as poor performance status, non-epithelioid histology, male gender, low hemoglobin, high platelet count, high white blood cell count, and high lactate dehydrogenase (LDH), can help clinicians and patients decide on a treatment plan 3. These factors can be used to identify patients who may benefit from more intensive or experimental therapy.
Imaging Modalities
Imaging modalities, such as computed tomography (CT) and positron emission tomography (PET), play a crucial role in staging MM 4, 5. Integrated CT-PET imaging can increase the accuracy of overall staging and improve the selection of patients for curative surgical resection 4. CT and MR imaging are of nearly equivalent diagnostic accuracy in staging MM, although MR imaging may be superior in revealing invasion of the diaphragm and endothoracic fascia 5.