Breast Cancer and Ovarian Cancer Link

What is hereditary breast and ovarian cancer?

Hereditary breast and ovarian cancer (HBOC) may be a possible diagnosis when there are multiple cases of breast cancer and/orovarian cancer on the same side of the family. The chance that a family has HBOC increases in any of these situations:

• One or more women are diagnosed with breast cancer before age 50
  
• There is breast or ovarian cancer in multiple generations on the same side of the family (such as mother and daughter)
  
• A woman is diagnosed with breast cancer twice or has both breast and ovarian cancers
  
• A male relative is diagnosed with breast cancer

What causes HBOC?

HBOC is a genetic condition. This means that the cancer risk can be passed from generation to generation in a family. Two genes are associated with HBOC: BRCA1 and BRCA2 (BRCA stands for BReast CAncer). A mutation (alteration) in either of these genes gives a woman an increased lifetime risk of developing breast and ovarian cancers. Men with these gene mutations also have an increased risk of breast cancer and for prostate cancer. Not all families with multiple cases of breast and ovarian cancer have mutations in BRCA1 or BRCA2. Research is ongoing to identify other genes associated with HBOC.

How is HBOC inherited?

Normally, every cell has two copies of each gene: one inherited from the mother and one inherited from the father. HBOC follows an autosomal dominant inheritance pattern, in which a mutation needs to happen in only one copy of the gene for the person to have an increased risk of getting that disease. This means that a parent with a gene mutation may pass along a copy of their normal gene or a copy of the gene with the mutation. Therefore, a child who has a parent with a mutation has a 50% chance of inheriting that mutation. A brother, sister, or parent of a person who has a mutation also has a 50% chance of having the same mutation.

How common is HBOC?

Most breast and ovarian cancers are sporadic, meaning they occur by chance with no known cause. Most women who have breast or ovarian cancer do not have HBOC. Current estimates are that less than 1% of the general population has a mutation in the BRCA1 or BRCA2 genes and only 10% to 15% of women diagnosed with breast cancer have one of these genes. HBOC is most frequently diagnosed when there are multiple cases of breast cancer and/or ovarian cancer on the same side of the family. In families with four or more cases of breast cancer diagnosed before age 60, the chance of HBOC is approximately 80%. To compare, the chance of finding HBOC when only one woman has had breast cancer diagnosed under age 50 is estimated to be 10% or less.

Individuals with Ashkenazi Jewish ancestry have an increased chance of having HBOC. Three specific gene mutations are common in this group:

• 185delAG in BRCA1 (also reported as 187delAG)
  
• 5382insC in BRCA1
  
• 6174delT in BRCA2

It is estimated that about one in 40 individuals with Ashkenazi Jewish ancestry has one of these three mutations.

How is HBOC diagnosed?

Families with multiple women diagnosed with breast cancer before age 50 and families with both breast and ovarian cancers may be considered to have HBOC. Mutations in the BRCA1 or BRCA2 genes can be diagnosed through a blood test. Since most breast and ovarian cancers are sporadic, genetic testing is only recommended for people who have a personal family history that suggests HBOC. Testing for mutations in the BRCA1 or BRCA2 genes may not be beneficial for the average woman.

What are the estimated cancer risks associated with HBOC?

Cancer risks for women with HBOC

• Lifetime risk of breast cancer 50% to 85%
  
• Risk of breast cancer before age 50 30% to 50%
  
• Lifetime risk of ovarian cancer
  • BRCA1 gene mutation 25% to 40%
  • BRCA2 gene mutation 15% to 27%
• There is also an increased risk of a second breast cancer diagnosis.

Cancer risks for men with HBOC

• Lifetime risk of breast cancer
  • BRCA1 gene mutation some increased risk
  • BRCA2 gene mutation up to 6%
• Risk of prostate cancer
  • BRCA1 gene mutation some increased risk
  • BRCA2 gene mutation up to 20%

• Men with a BRCA2 gene mutation have a significantly increased risk of developing prostate cancer before age 65.

Other cancer risks for people with HBOC

Both men and women with mutations in the BRCA2 gene may be at increased risk of other types of cancer, includingpancreatic cancer and melanoma. Researchers are investigating other cancer risks for men and women with BRCA1gene mutations, as well.