As part of an ongoing series of answers to common questions received by the Basser Center for BRCA, Executive Director Susan Domchek, MD, discusses hereditary cancer risk for BRCA mutation carriers and ways in which that might impact individuals differently.

Dr. Domchek: So we know that some families with BRCA1/2 mutations have a lot of breast cancer, some have a lot of ovarian cancer, and some have not much of either. And so one of the questions that we've always had is whether there's a way to individualize risk - meaning for any one individual, is their risk of breast or ovarian cancer at a specific level? And this is getting increasingly important, because we now are doing genetic testing in a lot more people and there are individuals that are found to have gene mutations that actually don't have a strong family history. So what's that all about?

There are several different factors here. One is that you can inherit things along with BRCA1/2 - things called SNPS, or single nucleotide polymorphisms. And each of these changes the risk of developing cancer by only a tiny little bit. So relative to BRCA1, for instance, these are very small risks. But we now know of about a hundred of them. And so when you add these all together, it is possible that these do modify risk. And by that I mean, for a BRCA1 carrier, if you have all the low risk SNPS, your risk may be as low as 40%, but if you have all the high risk SNPS, this risk may be as high as 90%. The question now is whether or not these are truly validated and whether or not these can help people make decisions and so research is underway to look at that.

Another aspect of individualized risk is that there are slight changes in risk depending on the specific mutation of BRCA1/2, meaning that certain areas of the BRCA1 gene have relatively higher risks of breast cancer than other areas. However, it doesn't seem that these are very clinically important, meaning the risks don't change that much compared to the range that we give.

So our ultimate goal is to combine environmental factors, personal reproductive factors, these SNIPS, and mutation-specific risk all together to give an individualized person a better sense of what their risk is.