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What Do Your Tumor Genes Say about Your Prospects? The Quest, Part 7

The views expressed are those of the author and are not necessarily those of Scientific American.


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Credit: CDC/Debora Cartagena

In the past couple of months, three people have told me that they or someone they love has cancer. Fortunately in each case, the tumors were caught early and some combination of surgery and radiation was all the treatment that was likely to be needed. Now, however, all three patients are waiting to hear what sort of genetic profile their tumors had.

Such genetic readouts are fast becoming the new standard of care in cancer treatment. Testing surgically removed tumors for the presence of certain mutations that a tumor has acquired during its formation is supposed to indicate whether or not this was a fast-growing cancer that is more likely to recur or metastasize. Because these tests are so new, however, it is not terribly clear what exactly—if anything—the results mean, or what should be done about them.

I’m going to spend the rest of this post pointing to basic information on cancer genetics. This is the foundation you’ll build on to understand the specific genetic profile of an individual tumor—whether your own or someone else’s. Future posts will include pointers for how to narrow the search even further.

First Steps

A quick search of MedlinePlus—my standard first stop on any search for reliable medical information—right away tells me this topic is full of landmines.

I type “genetic testing for cancer” in the search box and look at the first ten results.

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They are all about predictive genetic tests for cancer—which are performed in people who are currently healthy to give them an idea about their chances of developing a particular malignancy at some point in the future.

Those results are not at all what I want. I want to know about genetic tests performed on an already existing tumor after it has been removed. In other words, I don’t want a predictive genetic test; I want a diagnostic genetic test. And the fact that the default option for “genetic test” in MedlinePlus is all about predictive tests tells me that the diagnostic tests haven’t been around long enough or aren’t widespread enough to prompt someone at the National Library of Medicine to write the necessary disambiguation algorithms.

The way MedlinePlus is designed means that my next step is to broaden my search, going up the next most general level. Instead of “genetic testing for cancer,” I’m going to look for “genetic testing” all by itself and “cancer” all by itself. Then I’ll look for cancer links under the genetic testing results and genetic testing links under the cancer results.

 

1. Search for “Genetic Testing” followed by a scan for “cancer” terms

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The first result from a search for “genetic testing” brings me to a Health Topic Page, curated by the National Library of Medicine (NLM). Another way to get to the same destination is to click on “Health Topics” on the left of the page under “Refine by Type.”).

I always look for one of these topic pages if I can find one—the NLM has so far produced about 900—because if you scroll down the page, you’ll find a wealth of links that run from general overviews to more increasingly detailed sub-topics.

Under Overviews, I find some definitions from Mayo Clinic, which confirm my suspicion that there are multiple types of gene tests. The Mayo page also gives me a bunch of specific search terms for future inquiries, e.g. diagnostic vs predictive vs prenatal genetic testing.

The second result, from the National Institutes of Health, gives a wealth of information on various kinds of genetic tests and the federal government’s scrambling (my interpretation) to develop the regulations needed to ensure quality and commercial transparency. I’m still working my way through this cornucopia of information.

With these two overviews under my belt, I start scanning the list of links on the “genetic testing” topic page until I find my other search term—“cancer.”

Then it’s a matter of going through the links one by one—rejecting the links that talk about predictive tests, making note of the others that seem more relevant to what I’m interested in cancer diagnosis and prognosis (which is basically a forecast of the direction your cancer is likely to take—and, like weather forecasts, not 100% reliable).

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Following one link—from the Understanding Cancer series of the National Cancer Institute—gets me to a basic primer on gene testing and the relationship between DNA, genes, proteins and disease. Stills seems to be more about predictive than prognostic gene testing.

Another link on how gene testing is used in health care provides some general information and ideas about what the future may hold.

2. Search for “Cancer” followed by a scan for “genetic testing” terms

Now I want to follow my second search path to see what that turns up. Entering “cancer” in MedlinePlus’s general search box pops up a link for yet another NLM health topic page—this one on cancer. Click on that to generate another long list of links arranged from the general to the specific.

A side note: Obviously, if you are interested in a particular cancer, such as “breast cancer,” you can click on that under keywords. But I try not to skip the general search even when I’m on deadline; I often find it very helpful.

But back to the NLM’s “cancer” health topic page. I search the page (using Command-F on my Mac) for “gene” and sure enough am rewarded with a whole section on genetics.

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Wouldn’t you know the one that I find most interesting is from the same Understanding Cancer Series that I found under my general “gene testing” pathway. Only this one is Understanding Cancer Series: Cancer Genomics

Another side note: Maybe you already know what genomics means (it refers to how genes are “expressed,” meaning which genes are turned on or off); maybe you didn’t. But because you are systematically looking at everything with the word “cancer” in it, you won’t miss this one, which is basically a very detailed tutorial in the current state of cancer prognosis using genetic test results.

See especially these links, which supports my point above about how little investigators know about how to use genetic tests to determine future treatment or prognosis.

57. Cancer Susceptibility: Much Still Unknown

58. Epigenetic Changes: Much Still Unknown

59. Other Cancer-Associated Mutations: Much Still Unknown

60. Other Cancer-Associated Mutations: Much Still Unknown (cont.)

61. A Daunting Challenge

In upcoming posts, I’ll dig deeper into this wealth of information.

This post is part of a series called “The Quest: Practical Advice for Online Medical Searches.”

Click on the tag “how-to-search-medical-info” to get the whole series.

Previous posts include:

Six Facts About Aging and Aging Research

My 2 Favorite Tricks for Searching PubMed

Get the Lowdown on the Pills You’re Popping

$84,000 Miracle Cure Costs Less Than $150 to Make

How To Get A Medical Librarian to Do Your Search for Free

Practical Advice for Online Searches

 

 

 

 

 

About the Author: Christine Gorman is the editor in charge of health and medicine features for SCIENTIFIC AMERICAN. Follow on Twitter @cgorman.

The views expressed are those of the author and are not necessarily those of Scientific American.





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