What Is the Purpose of Diagnostic Tests?

Diagnostic tests are used to find out whether you have cancer. But they are also used for many other purposes, including to:  

Find out where the cancer started -- Diagnostic tests are used to locate the part of the body where the cancer started. This is important for choosing the appropriate treatment(s) and predicting what symptoms you are likely to experience.

Identify cancer cell type -- Cancer can involve one of several types of cells in a given part of the body. For example, bladder cancer may start in the transitional cells (cells that change their shape when the bladder tissue is stretched) or squamous cells (cells that line the bladder). Different types of cells grow at different rates and are likely to behave in different ways.

Learn whether the cancer has spread -- Cancer cells can spread from the place where they started to lympth nodes (small organs that help the body fight infection), organs near the place where the tumor started, or other parts of the body.

Predict symptoms and tumor behavior -- Diagnostic test results provide useful information about the symptoms you are likely to experience, whether your cancer is likely to spread, and how quickly it is likely to grow.

Choose appropriate treatment -- Different types of cancer respond differently to different kinds of treatment. By identifying the type of cancer you have, whether it has spread, and other features of the disease, diagnostic tests can help your doctor identify the best treatment for your disease.

Assess treatment effectiveness -- Certain diagnostic tests can be used to find out whether the treatment is shrinking your tumor. They can also show whether you still have cancer cells after you finish treatment.

Keep track of your health -- Once your cancer has been treated successfully, your doctor may order certain diagnostic tests on a regular basis to make sure that the cancer has not come back.