Breast Cancer Gene Marker

1. Labs: Gene Markers
   1. Most common types (>20 mutations have been identified)
   2. BRCA (BRCA1, BRCA2): 60% of Breast Cancer gene mutations
   3. AT (Ataxia telangiectasia) on Chromosome 11
      1. Single mutant copy
      2. Confers 5 fold risk of Breast Cancer
   4. PTEN gene (Cowden syndrome)
   5. CDH1 gene (hereditary diffuse Gastric Cancer)
   6. TP53 gene (Li-Fraumeni syndrome)
   7. STK11 gene (Peutz-Jeghers Syndrome)
      1. BRCA1
      2. BRCA2
2. Indications: BRCA testing
   1. Person with Family History of Breast Cancer or Ovarian Cancer and known BRCA mutation
   2. Ashkenazi jewish women
      1. 1st degree relative with Breast or Ovarian Cancer or
      2. Two 2nd deg. relatives with Breast or Ovarian Cancer
   3. Non-Ashkenazi women
      1. First degree relatives
         1. Two with Breast Cancer (at least 1 under age 50)
         2. One with bilateral Breast Cancer
      2. First or second degree relatives
         1. Three with Breast Cancer
         2. Comorbid Breast and Ovarian Cancer at any age
         3. Two or more with Ovarian Cancer
      3. Extended family
         1. Breast Cancer in any male relative
   4. Reference
      1. (2005) U.S. Preventive Task Force
3. Management: Known BRCA1 or BRCA2 carrier
   1. Risks of BRCA1 or BRCA2
      1. Breast Cancer risk: 85-90% lifetime risk
      2. Ovarian Cancer risk
         1. BRCA1: 40-60%
         2. BRCA2: 15-20%
   2. Management Options
      1. Surveillance starting at age 25 years
         1. Self Breast Exam Monthly
         2. Clinical Breast Exam every 6 months
         3. Mammogram yearly
         4. Breast MRI yearly (start at age 30 years)
      2. Ovarian Cancer screening
         1. No clear evidence-based guidelines
         2. NCCN guidelines (esp. BRCA1)
            1. Test every 6 months from age 35
            2. Tests
               1. Pelvic Ultrasound
               2. CA-125
      3. Prophylactic Mastectomy
         1. Breast Cancer can still occur
      4. References
         1. Garber in Harris (1996) Diseases Breast p. 335-41