Tag Archives: Genetics

23-not-for-me: My thoughts on direct-to-consumer genetic testing

As a geneticist, I’ve been studying the genomes and genetics of other individuals (and species) for years now. From time to time, I have been curious about learning about my own genome. What’s hidden in the base pairs of my DNA sequence and what does it say about me? Do I really want to know? What would I do with that information if I had it?

Now, anyone who’s willing to fork out $99* can get their genetic information easily through companies like 23andme. If you haven’t heard of 23andme yet, you will as they’re now advertising on television. It works like this: you spit in a tube and a month or so later, you find out if you carry genetic variants in your DNA that may be associated with increased risk for certain diseases, may affect your response to certain drugs or a number of other traits. You also find out information about your ancestry.

Just to be clear, you don’t find out the sequence of your entire 3 billion base-pair genome. You get sequence information for about 1 million sites that are known to vary among individuals (called Single Nucleotide Polymorphisms or SNPs, pronounced ‘snips’) and have been studied for association with various phenotypes (things we can detect in people, like physical traits or health conditions, that are a result of genetics or genotypes).

That sounds like a lot of data. And I love data!

So, am I going to spit in a tube and wait for my own genetic data?

I don’t think so! At least, not yet.

The major reason is that we have limited information to really understand the impact of different variants. Yes, we’ve been able to identify a lot of variation among humans and, yes, we’ve even done studies that link certain variants with an elevated risk for common health problems like diabetes and heart disease. But most of these studies show weak associations with modestly elevated risk of disease.

With a few exceptions, there is very little actionable information that one can learn beyond current recommendations for a healthy lifestyle. What would the recommendation be for someone who carries a variant that’s associated with elevated risk for diabetes or heart disease? The answer: healthy diet and exercise. What’s the recommendation for the general population to reduce risk of diabetes and heart disease ? The answer: healthy diet and exercise. And what if you find out that you’re not at risk for heart disease or diabetes based on the variants that were tested, does that mean you won’t get heart disease or diabetes? No, not necessarily! So how much does knowing you have these low impact variants actually help?

Let’s talk about data again. It is a lot of data. But is it enough? If the genetic testing tells you that you don’t have the variants that put you at risk for breast cancer, are you really safe? Having worked in this field, I know that there are literally thousands of mutations across tens of genes (that we know of so far) that can put you at risk for breast cancer. A negative result from a few variants tested in such tests may give someone with family history of breast cancer a false impression that they are ‘safe’ from the disease.

A big concern is that, for some folks, this kind of testing (direct-to-consumer) may take the place of traditional genetic testing which is done under the guidance of a physician and a genetic counselor, who can better interpret and explain risk of disease. Based on your family history, your physician and genetic counselor can determine if you need to get genetic testing done for disorders known to have strong genetic basis (like predisposition to breast cancer or Huntington’s disease). I would argue that knowing and informing your physician of your family history is paramount.

So what about you? Should you send away spit for your genetic information?

Sure, if you want. But, I would think of it mostly as entertainment only (for now). It could be fun to find out about your ancestral genetic background. My own family history can be traced back for a few hundred years but I might be curious to see who my ancestors were further back in time. And, one may argue that gathering genetic data from a large number of individuals may actually help us better understand impact of genetic variants. But as far as I know, there’s no medical history or medical tracking that’s associated with your genetic information, which would be needed those kinds of studies.

Bottom line, if you decide to fork out a hundred bucks, just be informed about how much weight to put in the information you get. I wouldn’t base any major health decisions based only on these sorts of tests. Personally, I would wait until there’s more information available that will help us better understand the impact of genetic variants that contribute modestly to disease states. And if you suspect you may carry a disease-causing mutation based on family history–talk to your doctor!

*Actual cost can vary depending on how long you want access to the data. The cost of the kit and testing is $99.

Angelina Jolie’s Story—An Incomplete Picture

In an op-ed piece in The New York Times, actress and director Angeline Jolie wrote that she recently had a prophylactic double-mastectomy to reduce the chances of developing breast cancer, a disease that took her mother’s life. She explained that she carried a “’faulty’ gene, BRCA1” which puts her at high risk for developing breast and ovarian cancer. She underwent the double mastectomy to reduce the risk of breast cancer by removing the tissues that generally give rise to tumors.

I heartily applaud Jolie’s documentation of a very personal experience on such a public platform in an attempt to encourage women with family history of breast and ovarian (and other) cancers to have open discussions with their medical professionals about genetic testing and possible preventative options that may be available to them. I can’t stress how important it is to have open conversations about scary health issues like breast cancer, especially since they may be tied with health, identity and possibly sexuality.

However, I must admit that as a scientist who studies BRCA1-associated breast cancer, I also felt a sense of alarm as I read the article. Many thoughts whirled in my head. Jolie’s focus on primarily breast cancer in women with BRCA1-mutations and double-mastectomy as a preventative option is far from complete. Though I respect Jolie for speaking openly about her personal matter, I feel that she and others who speak on such matters in public platforms have a responsibility to make the discussion as close to complete as possible. As a person of great influence, I wish she had provided a more complete picture, especially to a world in which medical and scientific information is often presented over-simplified to the brink of being inaccurate (more on this in another blog).

Below I attempt to touch on a few of the issues and questions that were largely ignored in Jolie’s piece.

Is it really that simple?

The article suggests that it’s quite straightforward: Everyone can go get tested for BRCA1 mutations and if positive for a mutation, can get a double-mastectomy and they’re cancer free! Let’s ignore for the moment that mutations in BRCA2, and a growing number of genes involved in similar cellular pathways, also lead to increased breast cancer risk. It also implies that mastectomy is the only preventative option available. Generally, women with family history or with known BRCA mutation are followed closely to allow early detection (and treatment) of breast cancer though they tend to have slightly higher risk of breast cancer (a yearly incidence of 2.5%) than those who have undergone prophylactic mastectomies (Meijers-Heijboer et al). Other, less invasive, options exist.

What is the impact on healthcare and more?

How many women without family history of cancer will visit their physicians and demand testing for BRCA? As Jolie mentions, the current cost of genetic testing for genes for breast cancer predisposition is over $3000. It is currently recommended for individuals who have family history of breast and ovarian cancer (and sometimes others) to have genetic testing to look for disease causing mutations and insurance generally covers this cost. We must think about the general impact on the cost of healthcare more broad genetic testing will have (at current costs), without even considering the cost of additional doctors’ visits by individuals at low-risk.

Another complication is what is known in the BRCA research and clinical community as ‘Variants of Unknown Significance’ or VUS. VUS refers to ‘mutations’ in BRCA1 that may just be changes in the gene that are not known to lead to cancer. We all carry differences in our genetic code in many of our genes compared to others in the human population. Many of these changes are benign—they don’t have any perceivable effect on our biology and health. We usually refer to changes in our genetic code that do have a perceivable effect on our health as ‘mutations.’ It is unclear whether a lot of the changes that are known to exist for BRCA are benign or real mutations. We must consider the potential scenario of a nervous individual with a benign VUS deciding to undergo major surgery like prophylactic mastectomy or oophorectomy (see below). Is the benefit in this case worth the physical, emotional and financial costs?

What about the ovarian cancer risk?

Discussing breast cancer (and preventative mastectomy) without a thorough mention of ovarian cancer for BRCA1-mutation carriers is an incomplete discussion. Jolie briefly touches on ovarian cancer risk; she does not provide it the weight it deserves. Granted I may have a biased perspective as a breast cancer researcher, I don’t perceive education on breast cancer in the US to be lacking. We are constantly inundated with emails, media campaigns, professional sports stars wearing pink athletic shoes, among other things that bring awareness to the real dangers of breast cancer. We have many options (with varying degrees of effectiveness) for early detection of breast cancer.

Ovarian cancer is a different beast. One of the biggest problems with ovarian cancer is that it is often not detected until it is progressed to an advanced stage. Chemotherapy and surgery are among the treatment options that can increase survival but the prognosis is generally not great, 5-year survival rates of 18-35% for aggressive, late-stage disease (American Cancer Society). For individuals with advanced risk, like BRCA1 mutation-carriers, prophylactic oophorectomy (preventative removal of the ovaries), which can accompany removal of other organs like fallopian tubes, is an option. But, it’s complicated. It’s a difficult decision since it can affect when a woman has children and has many long-term health complications including hormonal changes, increased risk for osteoporosis and cardiovascular disease. Furthermore, risk of ovarian cancer after surgery is lowered not eliminated.

I thank Angelina Jolie for sharing her personal story with women and opening up conversation about genetic testing for women at high risk. The story is much, much more complicated. It is imperative that those who have the knowledge and the platform inform the public in the most thorough way possible.

References

American Cancer Society: http://www.cancer.org

Meijers-Heijboer, H., et al. (2001) Breast cancer after prophylactic bilateral mastectomy in women with BRCA1 or BRCA2 mutation. The New England Journal of Medicine, 345 (3): 159-164.