How Genetic Testing Can Make Your Cancer Treatment More Effective

New drugs are better at targeting cancer cells

Drugs to treat cancer typically focus on the tumor’s location in the body. They bombard the cancer along with the healthy cells around it. But what if doctors could tailor cancer treatment just for you, based on the specific features of your tumor?

Advertising Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

That day is closer than you may think.

The Food and Drug Administration (FDA) recently approved a cancer drug that takes a promising first step toward treating cancer based on a patient’s genetic mutations — regardless of where the tumor began.

Cancer genomics — studying the genetics of a tumor — is an active field of research that aims to improve how doctors treat cancers in the future.

“This is the first step toward personalized medicine, designing a treatment regimen that is specific to that person and that tumor,” says oncologist Pauline Funchain, MD.

With a custom-designed treatment, drugs can better target cancerous cells without harming healthy ones, she says. And this means faster results and less harmful side effects.

Dr. Funchain answers three questions to help explain recent progress in cancer genomics and how it is changing the way doctors treat cancer.

1. What drugs are available to treat genetic mutations in tumors?

The FDA has approved more than 50 drugs that target genetic changes. And researchers are working on hundreds more, according to the National Foundation for Cancer Research.

“We have gotten great results from these drugs, and there are people alive today who wouldn’t be without them,” Dr. Funchain says. Some patients have been on the drugs for as long as five years, but the uses for those drugs continue to expand, she says.

Advertising Policy

In one example, the FDA previously approved pembrolizumab (Keytruda®) for patients with melanoma, lung and other tumors. In May, the agency approved Keytruda to treat patients with metastatic solid tumor that has certain molecular features — anywhere in the body.

Drugs like pembrolizumab work with your immune system to attack cancer cells.

Doctors used to choose cancer drugs based primarily on how well they worked for a group of patients. But now they can use a drug like pembrolizumab because it matches the genetic makeup of your cancer cells.

2. Which cancers undergo genetic testing?

Testing for genetic mutations is routine for patients with lung and colon cancer and melanoma, Dr. Funchain says.

For instance, a mutation found in some lung cancers (mostly in non-smokers) sometimes responds favorably to oral medication the FDA approved in 2015.

“The pill is fantastic,” she says. “Patients don’t lose all their hair.”

Doctors also recommend genetic testing for some patients with breast and ovarian tumors.

For instance, about 25 percent of breast cancers test positive for the HER2 mutation. Several new drugs are extremely effective in treating this fast-growing tumor, Dr. Funchain says.

Advertising Policy

The prognosis for HER2-positive patients has dramatically improved since doctors started prescribing these drugs, she says.

In another example, doctors used to treat chronic myeloid leukemia (CML) with a bone marrow transplant and chemotherapy or radiation. Now many patients with CML can take a pill that targets deadly cancer cells and leaves healthy cells alone.

Dr. Funchain says technicians often can use material from the original biopsy for genetics testing, as long as enough tissue is available. Test results also help doctors predict who is more likely to respond well to certain drugs.

3. Where do the ‘bad’ genes come from?

Dr. Funchain says patients frequently ask variations of this question: How did I get bad genes?

Here’s what she tells them:

Cancer is both a random and “bad luck” disease. If you smoke or don’t protect yourself from harmful sun rays you increase your chances of “bad luck.”

The body is constantly making new cells — healthy ones and ones with “typos,” or flaws, she says. Some typos are harmless and may just change the color of your hair, for instance. Others, because of their severity and location, may cause cancer.

“The Holy Grail of cancer treatment is to kill the tumor once and for all, and do it in a way with fewer side effects,” Dr. Funchain says. “Genetic testing is opening the door for that to happen.”

Advertising Policy