What Is a Predictive Marker?

A predictive marker is a genetic indicator that can shed light on how well a patient will respond to treatment. Research on the uses of predictive markers primarily involves cancers, particularly of the breast, but treatment for other diseases can be a target for well. Laboratory testing can be used to identify specific genetic regions of interest, whether researchers want to identify a new marker or screen a patient in the course of developing a treatment plan. Professional organizations of clinicians periodically release guidelines on the indicators they have identified and how to use them in therapy.

The type of information provided by a predictive marker can vary. Some may offer indicators that a tumor is chemo-resistant; chemotherapy may not be effective at all, or the chemotherapy options might be more limited. Others suggest susceptibility, or indicate that a tumor is highly likely to respond to a specific kind of chemotherapy. This information can guide the development of an effective treatment plan.

Using predictive markers makes it possible to tailor treatment to a patient. If a patient has a chemo-resistant tumor that is unlikely to shrink in response to any available treatments, it might make more sense to focus on resecting as much as possible and using radiation therapy to target lingering cells. Grueling sessions of chemotherapy can be skipped, because they may be unlikely to offer any benefits to the patient, and could degrade quality of life.

Conversely, a patient’s predictive marker might indicate that a specific drug or combination chemotherapy program could be highly effective. This would allow the patient to start getting the best medication possible very early in treatment, rather than having to try several regimens to find the right one. Attacking cancers early can increase the chance of success. Markers may also indicate whether the growth is likely to metastasize, and if a patient’s genetic relations are also at risk.

Cancers aren’t the only conditions that can benefit from predictive marker research. People infected with certain organisms like the Human Immunodeficiency Virus (HIV) and the hepatitis C virus can carry predictive markers that may provide information on how well they will respond to treatment. This can help their medical teams determine how to proceed with treatment, and may reveal which options would be the most appropriate for the patient's case. Additionally, a predictive marker may offer insight into prognosis and survival rates, which can be important for patients who want to make informed decisions.