Cancer.Net®: Doctor-Approved Patient Information from ASCO®

Genetic Testing and Cancer: An Introduction to Personalized Medicine

Jyoti Patel, MD; Member, American Society of Clinical Oncology: Genetic testing has really changed our approach to cancer.

Personalized cancer medicine means the right patient with the right drug at the right time.  And that’s really an interface of how can we develop a roadmap for patients based on host characteristics — so patient characteristics, tumor characteristics, so perhaps the genetic make-up or the proteins that are being expressed, and then the appropriate medicine that will take both of those factors into case.

We’ve made significant progress over the past decade of really cataloging some of the genetic changes that we see when cancer occurs. So there are particular mutations that may make someone more susceptible to developing cancer, there are other mutations that when detected in the tumor, cause a dysfunction of a particular protein for which we’ve developed drugs for. Personalizing therapy is looking for these markers in tumors, so understanding: Is there a protein that is over expressed? Is something malfunctioning that may make chemotherapy or targeted therapy more effective? And then really finding the right dose for the patient, finding the appropriate setting to give those agents in.

Genetic Testing for Family History of Cancer

Dr. Patel: Often patients undergo genetic testing if they have a family history of cancer.  And so this kind of genetic testing is looking to see if there is a germline mutation. So that’s a mutation that you inherently have, and that may predispose you to a particular cancer. And that’s relevant for people who have families in which cancer has been prevalent. 

The reason we want to know is to understand if we can screen or do preventative measures to decrease the likelihood of developing cancer.

Genetic Testing for Mutations and Proteins that Drive Cancer

Dr. Patel: The other big area in which cancer genetic testing has taken hold and really shaped how we approach treatments is looking for particular mutations that drive cancer.  Now we know that, that mutations are ubiquitous in cancer. That’s really how cancer forms, but what we’re looking for are a particular signature of mutations or particular driving mutation that may cause the cancer.

Some cancers are more commonly marked by particular mutations than others. So in lung cancer, we know that particular mutations in EGFR or ALK which are present only in the tumor cells can cause the cancer to grow and often the most appropriate initial therapy for those patients is an oral small molecule inhibitor of those proteins. So there are multiple ways that we can use testing in some cancers. It’s important to understand if there is a prevalence of mutations and in some cancers, it is standard of care to get mutational testing.

In other cancers, we don’t understand as much about the genetics or the prevalence of these particular mutations, the mutations that we can target is quite low, and that genetic testing may be done as part of a larger clinical trial or as a research effort. The other piece of testing that changes therapy for patients is a detection of particular proteins on their cancer.

We want to understand how we can find out which genes are the most important to target and which ones may be driving the cancer.

Another effort that we’re all making is to understand if we can find in the serum or in the blood particular proteins that are expressed or fragments of DNA that also may correlate with the treatment outcome.  So it may be that when someone has cancer, we’re able to detect particular proteins when the cancer has been effectively treated, either with surgery or immunotherapy or chemotherapy that that fraction of proteins goes down and we can monitor them over time.

Right now when we look to see if patients have disease recurrence we do it with a CT scan or a PET scan or a MRI. And although those tests are wonderful, generally if we can see something it’s more — it’s hundreds of thousands of cells. We’re now thinking about looking at cancer as really as a needle in a haystack using tests, not only from the blood, but from the urine, from the serum — to really treat cancer earlier, to detect cancer earlier, and we believe strongly that that will lead to better outcomes.

Understanding the Genetics of Your Cancer

Dr. Patel: When a patient first meets a cancer care team, I think it’s important to have shared decision making. So that means that the patient and the physician need to understand exactly what stage of cancer it is. To understand if there are particular genetic determinants of prognosis that may impact our first initial therapy or the likelihood of response, but then to take this information and really center it around what is important to you.

Where to Get More Information

Dr. Patel: The world of personalized cancer therapy is evolving rapidly. You can find out more about this field on Cancer.Net.

[Closing and Credits]

Cancer.Net®: Doctor-Approved Patient Information from ASCO®

ASCO's patient education programs are supported by Conquer Cancer Foundation of the American Society of Clinical Oncology. ConquerCancerFoundation.org  

Special Thanks:

University of Michigan Comprehensive Cancer Center

Medical Oncology Hematology Consultants Newark, Delaware

University of Nebraska Medical Center

The opinions expressed in the video do not necessarily reflect the views of ASCO or the Conquer Cancer Foundation.

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