Since the early 1990s we have known of the BRCA1 and BRCA2 genes which are the most common genes for hereditary breast and ovarian cancer. But over the subsequent years other genes have been found that also confer increased risk of breast cancer in particular. We have continued to learn about the BRCA1 and 2 genes so that we know, for example, quite a bit about the risk of cancer that these genes impart and we have management guidelines that include early detection. We start monitoring women as young as 25 with mammograms and breast MRIs and have good data to show that those are effective at early detection. We know that, for example, removing the ovaries of a woman while still premenopausal will reduce the risk not only of developing ovarian cancer but of death from ovarian cancer and reduce the risk of developing breast cancer and of dying from breast cancer. So we have a lot of data to work from.
We have learned also about other genes and now we have more testing that enables us to look at multiple genes at the same time for less cost but we know less about these other genes. So women who undergo testing, whether they have had a breast cancer diagnosis or are trying to avoid a breast cancer diagnosis can consider learning about their BRCA1 and 2 genes first, for example, and then about other genes or about all of these genes at the same time.
Part of the discussion today was about how we should incorporate genetic testing into care. Although the session was about prevention, so was devoted primarily to healthy women who are trying to avoid cancer, the discussion questions also came up about our cancer survivors and even about women at the time of cancer diagnosis using genetic information to help make decisions about surgery or about systemic treatment.
One of the main points I made in the discussion was that we have learned that family history is not as reliable as we have hoped. People tend to know about breast cancer in the family but not necessarily about age at diagnosis and certainly not about the type of breast cancer that might have been in a relative. The further you get from your parents and siblings and children, the less accurate the information. People know very little about ovarian cancer or colon cancer so family history is difficult. People have small families, they don’t always get cancer on schedule and it makes it hard to predict. So we do all have guidelines that speak of family history but as genetic testing becomes less expensive and more comprehensive it is becoming more reasonable to think about extending the guidelines for testing.
Do women need to consider their paternal heritage as well?
That’s very important. For many years we have all heard that you only have to worry about breast cancer if your mother’s family has cancer and that is not true. All of the genes for breast cancer susceptibility and, in fact, all of the genes for all of the inherited cancer susceptibility syndromes can be inherited from either parent. Paternal history is just as important.