Staging is the term used to describe the method for determining the anatomic extent of a tumor. Cancer staging assists the medical team in determining a patient’s prognosis associated with mesothelioma cancer, based on the location, size, involvement or spread within the body, cell type, tumor grade, and metastasis.
The process of cancer staging involves placing a patient into one of the four staging groupings. Each grouping has a section of overlap, which encompass the wide spectrum of the disease, with Stage I referring to early stage localized tumors, whereas Stage III refers to advanced stage tumors that have spread to other organs. The purpose of staging cancer is to allow medical professionals to define groups of patients who have similar prognosis which allows them to guide the patient to the appropriate treatment options. It can also help the medical team to develop a treatment plan, estimate prognosis and identify clinical trials for which each individual patient may be eligible. It is important that mesothelioma be properly staging in order to ensure the patient is receiving the appropriate treatment.
Staging your mesothelioma cancer, will occur twice in the process of your medical treatment planning. Once based on the clinical information available prior to surgery; this is referred to as clinical staging, and again after an operative surgical procedure, which will allow the medical team to more accurately provide precise anatomical information, called pathologic staging.
There are several different staging systems that were developed over time. As more and more information about mesothelioma becomes available and with additional scientific research through the use of clinical studies, how mesothelioma is staged will continue to change and evolve as the medical community gains more knowledge about how cancer and mesothelioma develops. Each staging system has its own positive features and drawbacks, and scientists continue to develop research programs to learn more about mesothelioma cancer and to reach a consensus over which staging system should be used. Some staging systems cover many different types of cancer, while others focus on more specific cancers.
The TNM (primary tumor, regional lymph nodes, distant metastasis) is the most widely used staging system for mesothelioma today, endorsed by the International Medothelioma Interest Group (IMG) and the American Joint Commission on Cancer (AJCC), though the other systems are still in use, or may assist along with TNM staging. This system combines all the research together and defines stage according to the extent of the tumor itself, the involvement of lymph nodes (or glands), and the presence of any metastases to other organs throughout the body.
Tests are generally performed to assist the medical team in determining the cancer stage of a patient’s tumor. Tests are either non-invasive, meaning they involve medical imaging or blood testing, or invasive, meaning that they involve a minor surgical procedure or image-guided biopsy. Imaging techniques such as x-rays, CT scans, MRIs and PET scans may show the location, size of the tumor and whether the cancer has spread. Laboratory tests will reveal blood, urine, tissue and fluid information that can assist in determining the stage of the cancer. Tumor markers which may become elevated when cancer is present can provide additional information.
Non-invasive tests may include:
Physical Examination: This will assist the doctor in determining the overall health of the patient and pinpointing signs of patient distress related to mesothelioma.
Serum Mesothelin: This measures the blood levels of a protein that is secreted by certain mesotheliomas.
Chest X-Ray: Defines the extent of the tumor within the chest.
CT Scan: Defines the extent of tumor but gives more detailed information than a chest x-ray alone.
MRI: This may be useful if chest wall invasion is suspected based on the CT Scan.
PET Scan: This is the most useful diagnostic test in determining whether the tumor has spread to other vital organs or other organs outside of the chest.
Invasive tests include:
CT-Guided Core Biopsy: This is an outpatient procedure used to assist in diagnosing mesothelioma.
Thoracentesis: This is an infrequently used outpatient procedure involving extracting and evluating the fluid from the chest. It may also be used to relieve symptoms, as well as be used for diagnostic purposes.
Thoracoscopy: This procedure involves general anesthetic and a small incision is made into the chest. This is the most accurate form of diagnosing mesothelioma.
Mediastinoscopy: This is an outpatient surgical procedure used to evaluate the lymph glands in the center of the chest containing the tumor, and involves a small incision made to the neck.
Endobrochial ultrasound needle biopsy: This is an outpatient procedure that evaluate the lymph glands in the center of the chest containing the tumor but does not involve surgery.
Laparoscopy: This is an outpatient surgical procedure used to evaluate if the tumor has spread to the abdomen.
As of 1976, a universally accepted staging system that categorizes patients into relatively homogeneous has been proposed. Two of these include specific descriptors of tumor node metastases (TNM), and the other three are based on a simple stage I through IV classification. None of these systems is completely validated or used uniformly for survival analyses. Recently, the International Mesothelioma Interest Group (IMIG) developed a surgically based TNM staging system that reconciles and updates previous staging systems by taking into consideration emerging information about the impact of T and N status on survival. However, even this new staging system is not fully validated.
The Butchart System is one of the older systems, based on identifying the extent of primary tumor mass and divides mesotheliomas into four stages. The Brigham System was the next staging system to follow, which stages mesothelioma according to resectability (the ability to surgically remove). The IMIG System was a precursor to the TNM System, which focused in on histological factors and lymph node involvement. The more recent International TNM System considers variables of tumor in mass and spread, lymph node involvement, and metastasis. Many cancer registries, such as the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program (SEER) use summary staging, a system used for all types of cancer based on five instead of four stage classification categories. Below is an oveview of all mesothelioma staging systems:
* Butchart System: extent of primary tumor mass
* Brigham System: (variables of tumor resectability and nodal status)
* IMIG System: In 1995, the International Mesothelioma Interest Group (IMIG) proposed a new staging systems for identifying mesothelioma. The IMIG System, which was a revitalized version of the TNM system, was a basic framework used to create what is now known as the International TNM system.
* International TNM System: — variables of T (tumor), N (lymph nodes), M (metastasis)
* Summary Staging: system used by organizations to stage cancer in general; also used for mesothelioma cancer.
Surgical Staging
Surgical staging may be performed depending on the patient’s health. Surgical staging is performed to determine lymph gland (node) involvement and the tumor spread. It especially helps in identifying whether the tumor has spread to the abdomen. This procedure will involve a singular outpatient visit to a surgical facility where a laparoscopy and endobrochial ultrasound will be performed, guided by fine needle aspiration. Occassionally thoracoscopy may also be required to obtain additional tumor tissue to confirm the mesothelioma diagnosis. In this particular case, patients may be required to stay overnight in the hospital and return home the following day.
Tissue samples allow for the tissue to be examined and reported back to the patient and medical teams in the form of a pathology report, which will notify the medical team of the size of the tumor(s), extension into adjacent structures, type of cells and tumor grade. Results of the examination of cells in fluid, such as that from a mesothelioma-related pleural effusion, may also provide information.
Pathology reports will notify the medical staff of specific markers favoring mesothelioma:
* Cytokeratin 5/6*
* Calretinin*
* WT-1*
* Thrombomodulin
* HBME1
* Membrane pattern with EM
* D2-40 (new)
* Podoplanin (new)
Lastly, surgical reports may provide information that may not have been relevant at the time of the previous surgery but may identify the existence of mesothelioma cancer or preexisting tumors, that were not identified at that time. The results of these tests will help to determine which therapy will be the most appropriate for your tumor.
