Search IconSearch

How Genetic Testing Can Make Your Cancer Treatment More Effective

New drugs are better at targeting cancer cells

genetic testing laboratory cancer

Drugs to treat cancer typically focus on the tumor’s location in your 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?


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.

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.

With a custom-designed treatment, drugs can better target cancerous cells without harming healthy ones, says oncologist Pauline Funchain, MD. 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.

In one example, the FDA previously approved pembrolizumab (Keytruda) for patients with melanoma, lung and other tumors. Then, the agency later approved Keytruda to treat patients with any metastatic solid tumor that has specific molecular features.


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. As more drugs are discovered, other cancers are also being considered for routine genetic testing. Dr. Funchain expects the testing to become routine for all cancers in the next 10 years.

For instance, a mutation found in some lung cancers (mostly in non-smokers) often responds favorably to oral medication the FDA approved in 2004. Since then several new drugs have been approved for for more recently discovered mutations, most recently in 2020.

“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% of breast cancers test positive for the HER2 mutation. Several new drugs are extremely effective in treating this fast-growing tumor, Dr. Funchain says.

The prognosis for HER2-positive patients has dramatically improved since doctors started prescribing these drugs, she says. Now HER2 drugs are being used for more tumors besides breast cancer.

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 genetic 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.”

Your 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.”


Learn more about our editorial process.

Related Articles

woman with metastatic breast cancer at office desk
Working While Living With Metastatic Breast Cancer

Working has its benefits, but it may require some modifications — and that’s OK

Tired cancer patient reading at night
February 27, 2024/Cancer Care & Prevention
The Link Between Insomnia and Cancer Treatment

Medications, tubing and stress can steal away the ZZZs you need

Older man and younger man talking over coffee at a cafe
February 21, 2024/Cancer Care & Prevention
Is Colon Cancer Hereditary?

Knowing your family history and getting a genetic test can help detect colorectal cancer earlier

two people standing at standing work desks
January 25, 2024/Cancer Care & Prevention
Can Sitting Too Much Increase Your Cancer Risk?

Studies show the high health cost of spending hours in a chair

person scratching at their itchy skin on their chest
January 3, 2024/Cancer Care & Prevention
Is Itchy Skin a Sign of Cancer?

Anything from minor irritations and chronic diseases to, yes, cancer can cause persistent itching

Female with red hair, freckles and light-colored eyes outside in the sun
December 22, 2023/Cancer Care & Prevention
Some Skin Cancers Can Be Genetic

Family history matters for melanoma, but the connection isn’t as strong for other skin cancers

Parents have a serious talk with child in living room on couch.
November 8, 2023/Cancer Care & Prevention
How To Tell Your Child That You Have Cancer

It’s important to share the news in an honest and age-appropriate way 

woman dyeing her hair
October 25, 2023/Cancer Care & Prevention
Can Hair Dye Increase Cancer Risk?

Research shows some associations and concerns, but no definitive connections

Trending Topics

Female and friend jogging outside
How To Increase Your Metabolism for Weight Loss

Focus on your body’s metabolic set point by eating healthy foods, making exercise a part of your routine and reducing stress

stovetop with stainless steel cookware and glassware
5 Ways Forever Chemicals (PFAS) May Affect Your Health

PFAS chemicals may make life easier — but they aren’t always so easy on the human body

jar of rice water and brush, with rice scattered around table
Could Rice Water Be the Secret To Healthier Hair?

While there’s little risk in trying this hair care treatment, there isn’t much science to back up the claims