Cancer is a genetic disease—that is, it is caused by changes in DNA that control the way cells function, especially how they grow and divide. These changes can be inherited, but most arise randomly during a person’s lifetime, either as a result of errors that occur as cells divide or from exposure to DNA-damaging carcinogens. These are referred to as “somatic” mutations or “acquired” mutations that are different from ‘germline’ or inherited changes.
Each person’s cancer has a unique combination of these genetic changes, and tumor DNA sequencing—sometimes called genetic profiling or genetic testing—is a test to identify these unique DNA changes.
Knowledge of the genetic alterations in your cancer can help determine a treatment plan. Some treatments—particularly, some targeted therapies—are effective for people whose cancer cells have specific genetic alterations that cause the cells to grow out of control (these are sometimes called “driver” mutations).
For example, mutations in the EGFR gene that make cells divide rapidly are found in some people’s lung cancer cells. A patient whose lung cancer cells harbor an EGFR mutation may respond to treatment with drugs called EGFR inhibitors. Clinical tumor DNA sequencing can reveal whether a patient’s lung tumor has an EGFR mutation.
Tumor DNA sequencing is at the crux of precision medicine: care tailored to the molecular characteristics of each patient’s disease.