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Wednesday, 23 February 2011

My genetic counselling appointment

I started this blog to compare my experiences of taking a genetic test on the internet and having NHS genetic counselling. I have previously written about my cancer scan with deCODEme and I have outlined my family history of breast cancer which led me to request a genetic counselling appointment. I have yet to write about the counselling itself.

So here is what happened: what I learnt, whether I was offered a BRCA test and why it turns out breast cancer isn’t what I should be worrying about.

Prior to the appointment, I filled in a family tree, fleshing out the cancer cases in my relatives. The two that concerned me were on my dad’s side of the family – his sister was diagnosed with breast cancer in her 40s and his mother had a double mastectomy at age 31.

At the appointment I was given background information on the differences between hereditary cancers which tend to strike younger people and those due to the lottery of aging, which are more common after age 60. Each case of early onset cancer in my family was given a score (based on things like the age it was diagnosed, the type of cancer) and the cumulative score provided my individual risk.

Given the two cases in my family, I was assigned a lifetime risk of 17-30%. This is “moderate”, and should be compared to the average of 11%. BRCA tests on the NHS are given when the likelihood of testing positive is greater than 10%: the chance of finding such a mutation in me was estimated at 1.5% (and 7% in my aunt), so I was not offered the test.

The family tree information I had provided extended to my grandparents, but I had no information about their siblings. If it was indeed the case that my paternal grandmother was a BRCA mutation carrier and that she passed the gene to her daughter then there would be other cases of breast or ovarian cancer in her family (BRCA mutations tend not to hide their phenotypes shyly in the corner). Any new cases would increase my personal score.

I went away from the counselling session and spoke to my mum. She told me that my paternal grandmother’s parents and her siblings (a sister and brother) had all died in their 60’s, but not from cancer. My paternal grandmother had two female aunts that both lived well into their 80s.

This is not a typical BRCA mutation carrying family. I found such extra information hugely reassuring, it gives me no reason to believe that I am carrying a nasty ontological time bomb.

How do the results compare with my deCODEme DNA profiling? It is important to note that the deCODEme test did not look at BRCA itself but at other short regions of DNA that are statistically associated with breast cancer. The deCODEme result gave me a lifetime risk of 11% - significantly lower than that from my counselling and slightly below the deCODEme lifetime average of 12.5%.

It is a bit unfair to compare the internet and NHS results as they are measuring two very different things, and both in very crude ways. The NHS number was based on two occurrences of early onset breast cancer in my family, the deCODE number was a sum how associated the sequence of a handful of base pairs in my DNA are with breast cancer.

Although both came out with answers in the form of numerical values, I don’t put much value on either of the figures. The most worthwhile part of the exercise was the follow up - the lack of breast/ovarian cancer in my more distant relatives makes my odds of catching the disease seem pretty much average.

The two procedures were very different - family tree building means taking time to talk to people and hunt down information, whereas genotyping involves a click, a credit card and a consumer buzz. For those impatient, affluent and not a fan of family conversations, the computer wins hands down, but, for me, old fashioned tree building felt more meaningful. This result wasn’t as precise as a number, but it was a much more valuable in terms of personal knowledge and understanding.

There is, however, a small sting in the tail. I found my paternal grandmother’s parents and two siblings all died in their 60s. They were all killed by high blood pressure related illnesses - strokes, heart attacks - even the women. A dispassionate look at my extended family tree suggests I should not be worried about cancer, but that I should get my blood pressure checked regularly.....


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4 comments:

  1. Nice post - was it Tyrer-Cuzick (IBIS) model used for personal risk score or BOADICEA? both give slightly different estimates.
    I assume you should multiply the relative risk score derived from decodeme scan (0.89) with your NHS risk - the result would be the best estimate.

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  2. Hi Ramunas - no idea about the model used. I have emailed my counsellor and will fill you in if I hear anything back. Elaine

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  3. I don’t suppose many of websites give this kind of information.
    www.renaissancelifetherapies.com

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