In the three weeks since I wrote about my experience with genetic testing, I’ve been inundated with emails. 

Some doctors asked for more details on my symptoms. A finance executive wanted to know more about my testing recommendations and then argue with me about them (it’s fine, we’re old friends.) And a fair bit of survivors wanted to ask about insurance and costs.  

But the overwhelming amount of emails came from survivors who had been diagnosed more than a decade ago. People who never had genetic testing and are now trying to figure out what they should do.  

I was surprised by both the amount of questions and the lack of knowledge about genetic testing. So much so, that I think a primer is in order. 

There are two main types of genetic testing a cancer patient or survivor may encounter. One is called saliva or germline testing. This examines a person’s genetic code to identify inherited mutations that makes them predisposed to certain diseases. 

The second is tumor genetic testing, where tumor samples taken during a biopsy are examined for changes that may have occurred during a person’s lifetime. That information can help doctors determine if certain therapies will work, or may not. 

Given tumor genetic testing largely relates to treatment policies, survivors worried about recurrence or new cancers should focus largely on saliva or germline testing.

Absolutely not. 

For years, doctors thought of cancer as a genetic disease. Whether you got or didn’t get cancer was largely out of your hands. 

But increasingly, researchers have learned that genes are only a part of the cancer equation. Your diet, physical health and environment also play these massive roles in preventing cancer and cancer recurrence. 

So, by learning your genetic makeup, doctors, nutritionists, therapists and others can create screening, treatment and lifestyle plans to counteract your genetic risk. They can also recommend those changes to other people in your family. 

Guidelines for who exactly should get tested are determined by the National Comprehensive Network, NCCN. The group’s recommendations look at type of cancer and age and several other factors. They are followed by hospitals and insurance companies and are the same whether the person being tested is a patient or a survivor. 

At nearly every cancer hospital I spoke with, if you get a positive test result, you are then referred to a high-risk genetics clinic. Some even have high risk clinics for specific cancer, like kidney or gastrointestinal cancers. 

Whitney says counselors are helpful given everyone responds so differently. Some people have a 5% risk of getting cancer and think they’ll definitely get cancer. Others have a 50% chance and don’t care at all. 

Some survivors even get angry when they get a negative result, desperate to find a reason for why they got cancer. If that’s you, know your anger is common. We are all searching for the reason. 

Both your emotions and the actual results can be difficult to make sense of and it’s best to have someone to help. 

A genetic test report will include the following five sections. Below is a description of what you will find in each section, with special thanks to the team at Mass General Brigham for their many contributions to this cheat sheet.

Main results and summary

Positive: The testing detected a genetic variant that is likely disease causing. 

Negative: No genetic variants were detected.

Inconclusive: Genetic variants were detected but we do not know the impact of that variation. Often, this will be categorized as a variant of uncertain significance. 

Variant nomenclature

Transcript: Typically starts with NM_ followed by a set of numbers. One gene can have many transcripts – the combination of exons and introns that make up our mRNA. 

Coding: The specific nucleotide change on the DNA sequence.

Protein: The amino acid change at the protein level. 

Gene information

This section will include the gene name, the disease that this gene is associated with, relevant publications that support the connection, and the inheritance pattern of related conditions. 

The section will also discuss whether the gene is recessive (this is when both copies of a gene must be affected to have a condition) or dominant (when only one copy of the gene needs to be affected.)

Variant Pathogenicity Information

This section will include the evidence used to determine the pathogenicity – a medical term for how scientists believe this genetic variant potentially causes disease – of the variant. 

Sections include population database, literature and publications, in silico predictors (the computational tools used to predict disease), and functional studies. There may also be a recommendation here for additional family testing to confirm presence or absence in family members. 

Methodology and Limitations

A heavily technical section that outlines information about how the test was conducted and any limitations. This can be helpful in the future as we learn more about genetic markers and you evaluate whether you should retake a genetic test.