The stage of a cancer is a descriptor of how far cancer has spread in its course. The stage of the cancer typically takes into account the size of a tumor, how deep into the tissue it has penetrated, if adjacent organs have been affected, and whether it has metastasized or spread to other organs. The staging of cancer through the use of imaging tests like x-rays, CT scans and MRI scans is crucial because the stage at diagnosis is the best predictor of survival, and the best way to determine the course of treatment. Correct staging is also critical as it directly influences treatment options available to patients. If a patient is staged incorrectly serious complications can arise, including improper treatment and diminished patient survival. Pleural mesothelioma, as the most common and easiest to study, is the only type of mesothelioma that has a staging classification.
The Butchart staging system is based on tumor mass, dividing mesothelioma into stage I through IV. It is still the most commonly used.
- Stage I – mesothelioma is present in the left or right pleura and could involve the lung, pericardium or diaphragm on the same side.
- Stage II – mesothelioma has invaded the chest wall or involves the esophagus, heart, lymph nodes or pleura on both sides.
- Stage III – mesothelioma has entered the peritoneum and lymph nodes beyond those in the chest may be involved.
- Stage IV – there is proof that mesothelioma has spread through the bloodstream to other organs.
Another staging system developed by the American Joint Committee on Cancer (AJCC) called the TNM system is similar to the same staging systems used on other cancers. The T – means tumor (its size and how far its spread). The N – means it’s spread to lymph nodes. The M means – metastasis – and has spread to distant organs.
There are minor differences between the two systems. TNM stages are:
- Stage I – mesothelioma is present in the right or left pleura. It may have spread into the lung, pericardium or diaphragm on the same side. The lymph nodes are not involved.
- Stage II – mesothelioma has spread from the pleura on one side to the nearby peribronchial and/or hilar lymph nodes next to the lung on the same side. It may have spread to the lung, pericardium or diaphragm on the same side.
- Stage III – Mesothelioma has spread into the chest wall muscle, ribs, heart, esophagus or other organs in the chest on the same side as primary with or without having spread to lymph nodes on same side.
- Stage IV – Mesothelioma has spread into the lymph nodes in the chest on the side opposite that of the primary tumor or directly extends to the pleura or lung on the opposite side, or into the peritoneum or in the abdominal cavity and organs.
Another recently developed system is the Brigham System. The stages for this system are based on the ability to surgically remove the tumor and the involvement of the lymph nodes. There are four stages.
- Stage I – mesothelioma is able to be removed and there is no lymph node involvement.
- Stage II – mesothelioma can be surgically removed but with lymph node involvement.
- Stage III – presence of mesothelioma that can’t be surgically removed extending into the chest wall, heart, or through the diaphragm or peritoneum. At this point, it doesn’t matter if there is extra-thoracic lymph node involvement.
- Stage IV – cancer is widespread throughout the body.