Hereditary Breast and Ovarian Cancer

Hereditary Breast and Ovarian Cancer Syndrome (HBOC)

What is HBOC?

Hereditary breast and ovarian cancer syndrome (HBOC) is characterized by a high risk of breast and ovarian cancers. Two genes are associated with the majority of HBOC families: BRCA1 and BRCA2. BRCA stands for BReast CAncer. A woman with a BRCA1 or BRCA2 gene alteration (mutation) has a 60-80% risk of developing breast cancer, whereas the risk for an average woman is about 13%. A woman with a BRCA1 gene mutation has a 50% risk of developing ovarian cancer and a woman with a BRCA2 gene mutation 20%, whereas the normal risk for an average woman is about 1-2%.

What causes HBOC?

A mutation (alteration) in either BRCA1 or BRCA2 gives a woman an increased lifetime risk of developing breast and ovarian cancers. Men with these gene mutations also have a small increased risk of breast cancer and prostate cancer. There is a small increase in the risk of other cancers including pancreatic cancer and melanoma among carriers of BRCA1 or BRCA2 mutations.

Not all families with multiple cases of breast and ovarian cancer have mutations in BRCA1 or BRCA2. Other, less common genes have also been associated with an increased risk of developing breast and other cancers. Some of these (PTEN and TP53) are include in Thematic disease group 4 other rare genturis.

Genes linked to ovarian cancer include RAD51C, RAD51D and the Lynch syndrome genes. There is also the possibility of increased genetic risk due to the combination of multiple low-risk genetic alterations (called polygenic risk).

How is HBOC inherited?

The risk of transmission of the inherited altered gene copy from the affected parent to the offspring is 50%, regardless of the gender. 

What are the surveillance options?

The surveillance depends on the level of the risk which varies on which gene is involved and the family history of cancer.

Breast surveillance should begin at age 25-30 with clinical examinations, mammograms and breast MRI.

Besides screening, preventive surgical removal of both breasts can reduce the risk of breast cancer by more than 90%. Only about 3% of breast cancers associated with BRCA1/2 mutations are diagnosed before age 30, so surgery could be deferred to over the age of 30 for most women.

Screening for ovarian cancer does not guarantee early detection and is not routinely recommended. Preventive surgical removal of the ovaries and fallopian tubes can reduce the risk of ovarian cancer by approximately 90%.

Link to more information about HBOC    


Clinical practice guideline

Currently unavailable

Care pathway

Care pathway - Hereditary Breast and Ovarian Cancer (HBOC)

Patient journey

Patient journey - Hereditary breast and ovarian cancer (HBOC)