Using genes in diagnosis, prognosis and treatment

Researchers study genes to help them learn more about which ones may be linked to cancer. They have mapped all of the genes that make up humans (called the human genome). Doctors are now using the human genome and better gene-based tests to study DNA and better understand cancer. Doctors can test for certain genetic changes during diagnosis to help them confirm that a person has cancer. It can also help them predict the outcome (prognosis) and plan treatment.

Studying genes in people with cancer has also led to:

• new ways to classify cancer
• using genes as biomarkers to help diagnose cancer
• helping doctors predict and monitor a person’s response to treatment
• helping doctors tailor treatment based on a person’s gene mutations
• developing new drugs that target specific gene changes

Researchers have found links between many genes and certain types of cancer. They have shown that different cancer types can share the same gene mutations. For many years cancers have been grouped by the organ in the body where the cancer first starts to grow and what the cancer cells look like under a microscope. But more recently, doctors are also grouping cancers based on their gene mutations. This has helped doctors predict who may develop cancer and how well a treatment is likely to work. It has also helped to develop new treatments that target specific genetic changes.

Doctors can test for certain genetic changes during diagnosis to help them confirm that a person has cancer. Researchers are also using special gene-based tests to look at many genes at once in people with cancer. Microarray analysis allows researchers to see which genes are turned on and which ones are turned off. Analyzing many genes at the same time to see which are turned on and which are turned off is called gene expression profiling.

Studying genetic changes can also help doctors predict which people with cancer are likely to have a better or worse prognosis. Knowing a cancer’s gene mutations can help predict which cancers are most likely to come back (recur) after treatment and which people are most likely to benefit from treatment or a certain type of treatment. Information about genetic changes can help doctors to know how well treatment is working and can also help them predict which patients are most likely to have side effects from a treatment.

People with the same type of cancer won’t have the same response to a treatment. Personalized medicine allows doctors to choose each person’s treatment based on a cancer’s genes, proteins or other molecules (called the genetic or molecular profile). This personalized treatment may make it more likely that a treatment will work better. It may also lead to fewer side effects from treatment or make the side effects less severe.

When a tumour is removed from the body after a biopsy or surgery, it is sometimes tested for certain genes or proteins that are known to be linked to cancer. People who have certain genetic changes may benefit from targeted therapy. And studying gene mutations may help researchers develop new targeted therapy drugs.