Straight Talk about Mesothelioma, a blog series created by Michael T. Milano, M.D., Ph.D., a radiation oncology specialist, as a resource for mesothelioma patients and their loved ones.

Hearing that you or a loved one has mesothelioma is shocking and devastating news. With little chance of cure, many different kinds of mesothelioma, and a variety of treatments, there are a number of questions that arise when one is diagnosed. One of the primary steps in answering these questions is determining the stage, or how far along the disease has spread. The cancer stage will help determine appropriate treatment options. The diagnosis and staging of mesothelioma can be completed through one or more tests, which then allow the physician to prescribe the proper treatment plan.

What Tests Are Used to Determine the Stage of Mesothelioma?

There are a few main tests and procedures that help determine the stage of mesothelioma:

Computed tomography scan (CT or CAT scan): A procedure that uses x-rays to make detailed cross-sectional images, or a series of detailed images taken from different angles of the body.

Positron emission tomography scan (PET scan): A procedure that uses a small amount of radioactive glucose, or sugar, injected into a vein in order to take a picture of where glucose is being used in the body. Because malignant tumor cells are more active and take up more glucose than normal cells, they appear brighter in the picture.

Endoscopic ultrasound (EUS): A procedure in which a thin, tube-like instrument with a light and lens is used to look inside the body. A probe at the end of the instrument, or endoscope, bounces high-energy sound waves off the tissues and organs to make echoes, which are used to form a picture, or a sonogram.

What Is the TNM Staging System?

The most common type of mesothelioma, pleural mesothelioma, is the only kind that has a formal staging system. The American Joint Committee on Cancer (AJCC) tumor (T), node (N), metastasis (M) (TNM) staging system is universally used in the US and elsewhere. This system is based on 3 parts: 1) The extent of spread of the main, or primary, tumor. 2) The spread of cancer to nearby, or regional, lymph nodes. 3) The spread, or metastasis, of cancer to other organs of the body. The 3 parts are then assigned a number with higher numbers meaning the cancer is more advanced. Once the T, N, and M categories have been established, this information is then used to conclude what stage of cancer the patient is in.

What Are the Stages of Mesothelioma?

The 4 following stage groups (based upon the TNM stage) are used to describe how advanced the cancer is:

Stage I: The cancer is localized to one side of the chest in the lining of the lungs and/or chest wall.

Stage II: The cancer has grown into the diaphragmatic muscle and/or lungs.

Stage III: The cancer is more locally advanced in the chest than Stage I-II, but still potentially resectable and/or involves lymph nodes on the same side as the tumor or middle of chest.

Stage IV: The cancer involves the pleural lining of both lungs, has multiple diffuse masses in the chest, invades through the heart lining, invades mediastinal organs (trachea, esophagus, heart) or spine, has spread to distant lymph nodes and/or other organs.

Mesothelioma is a scary diagnosis. Doctors use a wealth of tests to define and describe exactly what cancer you are dealing with. With accurate cancer staging your doctor can understand the what, where, and when of the disease in order to decide the best plan to treat the cancer.