Dear Dr. Roach: I am a healthy 63-year-old woman. My 29-year-old niece was just diagnosed with metastatic breast cancer. She discovered that she carries a mutation of her CHEK2 gene. Her father, who is my brother, also has the gene. Should I get tested for the gene and should my children be tested? What can you tell me about the CHEK2 gene? — D.E.

Answer: Many genetic mutations have now been associated with breast and other cancers. Probably the best known are the BRCA1 and BRCA2 genes, but CHEK2 is one of many others that increase the risk of developing breast cancer.

CHEK2 is the gene that codes for an enzyme called checkpoint kinase 2, which helps repair DNA. If this enzyme is damaged, cancers are more likely to develop. The most severe mutation is called the 1100delC protein-truncated variant. Six percent of women with this mutation will develop breast cancer by the age of 49, and 32% will have been diagnosed by the age of 80. Your niece was, sadly, very unlucky. This mutation also doubles the risk of colon cancer.

Women with this gene mutation should undergo more intensive screening for breast, ovarian and colon cancers. Men with this gene mutation, like your brother, are at risk for male breast cancer, as well as stomach, prostate, kidney and thyroid cancers.

Since your brother has the gene, you also had a 50% chance of having it at birth (your risk now is slightly less, since you haven’t had a CHEK2-associated cancer). It is worth talking to your doctor about a referral to a genetic counselor to consider the consequences of testing for the gene. Knowing you have it is likely to affect how you get screened, and perhaps your childrens’ screening as well. There are treatments to reduce the risk of developing breast cancer in women with this gene mutation.