Breast and Ovarian Cancer Syndrome
Hereditary breast-ovarian cancer (HBOC) refers to families in which breast cancer and ovarian cancer are diagnosed frequently. It is possible that either one individual suffers from both cancers or several individuals in the pedigree suffer from one or the other cancer type. In such a case we suspect a hereditary factor to cause the pattern of breast and ovarian cancer occurrences in the family.
The two most common genes that are known to cause HBOC are BRCA1 (on chromosome 17) and BRCA2 (located on chromosome 13).
- BRCA1 is a tumour suppressor gene that was first described in 1990. In its mutated form it causes breast cancer (up to 60% lifetime risk) and ovarian (up to 55% lifetime risk) cancer. Regularly BRCA1 becomes active from age 35 years onwards.
- BRCA2 mutations also cause breast (up to 60% lifetime risk) and ovarian (up to 25% lifetime risk) cancer. Regularly BRCA2 becomes active from age 40 years onwards.
Risk assessment includes a family tree (pedigree) but family history is false negative in approx half of the cases. It is especially misleading in small families, in families with a low number of females, in families with adoption or if non-paternity could be an issue.
Genetic testing is indicated if the female concerned carries a 15% risk of carrying BRCA1 or BRCA2. Genetic testing involves a blood test. It is available in QLD publicly or privately (cost $3500).
Latest research from the Australian Ovarian Cancer Study (March 2011) confirms that 16% of all ovarian cancers are BRCA-related (inherited). This percentage is far larger than anticipated. It follows that all patients with (serous) ovarian cancer should be tested for BRCA1 and BRCA2. The implications for the patient’s family will be more significant than for the patient herself.
Clinical management options
Breast: Breast cancer screening, prophylactic surgery (mastectomy)
Ovaries: screening (very unreliable because ultrasound and tumour markers frequently are both, false positive and false negative); risk-reducing prophylactic surgery (>90% reliable, definitely recommended for women >40 years of age). Prophylactic surgery also reduces the risk of breast cancer. The earlier the ovaries are removed the higher is the protection against breast cancer.
Prophylactic surgery should be performed by an experienced laparoscopic surgeon. Both ovaries and tubes need to be removed completely through a retroperitoneal approach because BRCA-related cancers often arise in the fallopian tube. Most patients request a hysterectomy at the same time, which also can be done laparoscopically. Prophylactic surgery will induce instant menopause if performed on a premenopausal woman.
Lynch syndrome is an inherited cancer syndrome causing uterine, bowel, stomach and urinary tract cancers. Patients with Lynch syndrome have a 40% to 60% risk of developing uterine cancer and risk of 5% to 12% of developing ovarian cancer.
Often, patients who carry Lynch syndrome are younger and know other family members who developed different types of cancer (stomach, bladder, bowel, uterus, ovarian).
Patients who were diagnosed with uterine cancer at 50 years of age or less have an 18% chance of carrying Lynch syndrome. These patients require regular screening (e.g., colonoscopies) for the other cancer types.
Patients who were diagnosed with Lynch-related bowel cancer have a 25% risk of developing subsequent uterine or ovarian cancer. In these patients prophylactic, risk-reducing surgery to remove uterus, tubes and ovaries can be life-saving. These operations are done laparoscopically (key hole) and virtually eliminate the risk of uterine and ovarian cancer.
The first step to diagnose Lynch is an immunohistochemical test that can be done from the surgical specimen from the original uterine or bowel cancer specimen. This test is not diagnostic. However, if the test is positive, confirmatory testing should be instigated and requires a blood test. Referral to a Family Cancer Clinic is recommended.
Colonoscopy (every 1 to 2 years) from age 25 years (reduces colon cancer incidence and mortality by >60%)
Annual urine cytology (to detect early stages of bladder and ureteric cancers)
Endometrial sampling (yearly) only for young women who have not completed a family
Prophylactic surgery (laparoscopic hysterectomy) is the most effective way to eliminate the risk of uterine cancer; it virtually eliminates its risk and should be performed by an experienced laparoscopic surgeon.