Home  >  Health Encyclopedia  >  Cancer Care

Health Encyclopedia


Cancer Care

Breast Cancer—Understanding Genetic Testing

Breast Cancer - Understanding Genetic Testing

Cancer is a disease of the genes. Most cancers develop as a result of genetic damage or a mutation that happens sometime during a person's lifetime. These are called sporadic cancers. These types of mutations only affect the cells that grow from the original mutated cell.

Young woman

The risk of developing cancer is higher in people who are born with certain genetic defects that are passed on from their parents and found in every cell in their body. These defects occur in areas of the DNA that affect cell division, cell death, and the repair of damaged DNA. Cancers that result from DNA damage that is passed on are called hereditary cancers. They account for about 5% to 10% of all breast cancer cases. The likelihood of breast cancer being hereditary is linked to your age at the time of diagnosis. The younger you are, the more likely the cancer is hereditary.

The National Cancer Institute describes genes as "nature's blueprints for every living thing." Genes determine your body's potential for function and growth. Environmental factors influence the outcome. For example, a woman might have the genetic potential to be 6 feet tall. However, if she has poor nutrition as a child, she may not reach that potential. Similarly, a woman may have a genetic risk of developing breast cancer. Whether she develops it or not may be influenced by environmental exposures she has during her lifetime.

Genes come in pairs. One set is passed down (inherited) from your mother and the other set from your father. Genetic risks and potential can come from either parent.

A number of genetic defects can result in an increased risk for breast cancer. All these defects occur in areas of the genes that influence cancer progression. The most common defects are found on genes named BRCA1 (breast cancer gene 1) and BRCA2 (breast cancer gene 2). A woman who has inherited a harmful mutation in BRCA1 or BRCA2 is at higher risk of developing breast cancer and some other types of cancer than a woman who does not have such a mutation. The discoveries of these breast cancer genes in the early 1990s greatly helped our understanding of the genetic basis of inherited breast cancer and ovarian cancer. However, these are large and complex genes. Scientists continue to work to understand the significance of different alterations in these genes.

Researchers at the National Human Genome Research Institute have developed tests using DNA microchip technology that can distinguish between hereditary and sporadic forms of breast cancer. Additional tests using DNA microarray technology assess how active the many different breast tumor genes are at the same time. This will help researchers classify tumors based on gene activity and help design treatment strategies to target each individual type of tumor. 

Deciding on genetic testing for breast cancer

Genetic testing is considered only for women with a certain family history. You might fall into this high-risk group if any of the following statements are true for you:

  • You have 2 or more close relatives with breast cancer.

  • You have relatives who developed breast cancer before age 50.

  • You have breast cancer in more than one generation in your family.

  • You have several family members who have had ovarian cancer.

  • You are of Ashkenazi (eastern and central European) Jewish ancestry.

If you are considering genetic testing for cancer risks, you face many complex issues. If you test positive, you will face difficult decisions about treatments to prevent breast cancer. You may have increased anxiety about developing breast cancer. You may have concerns about losing your health insurance coverage. If you test negative, you may also face difficult challenges, such as survivor guilt, if other family members have tested positive.

However, if you are anxious or considering preventive surgery based on your family history, having the results may be very helpful. Because of these issues, you should seek genetic counseling before, during, and after any genetic testing.

If you test positive, what can you do?

If the doctor finds a mutation in the BRCA1 or BRCA2 gene, you can consider several options. You may be advised to be more aware of early-detection measures, such as regular breast self-exams, more frequent clinical breast exams, and mammography along with breast MRI. Experts have different recommendations for breast self-exams, clinical breast exams, and mammography. Women should talk with their doctor about their personal risk factors before making a decision about when to start getting these exams or how often they should get them. Or you may make lifestyle changes, such as cutting back on alcohol, stopping smoking, increasing exercise, and improving your diet. These steps may help reduce your breast cancer risk and improve your overall health.

More drastic options include removing the areas at high risk for cancer development. Surgically removing the breasts to prevent breast cancer, called prophylactic mastectomy, is one option. This procedure dramatically reduces the risk for breast cancer. Many women are surprised to learn that it does not completely eliminate the risk because it is impossible to remove all the breast tissue without doing an extremely radical surgery.

Depending on the type of genetic mutation, you may also want to consider surgically removing the ovaries to prevent ovarian cancer. This type of surgery is called an called oophorectomy. It also dramatically reduces the risk for cancer, but does not entirely eliminate it. 

These drastic measures are designed to affect a woman's lifetime risk of developing either breast or ovarian cancer. These are not decisions to make overnight. Make them, instead, with a lot of information, counseling, and support to assess all your risk factors, concerns, goals, and values. For example, if you want children, genetic counseling may guide you in the decision to first have children and then proceed with prophylactic surgery.

Related Items
Wellness Library
  Solving the Breast Cancer Puzzle
  Reducing Your Risk for Breast Cancer
  Certain Factors Help Predict Invasive Breast Cancer
  Hope on the Horizon for Breast Cancer
  Stay Healthy After Breast Cancer
Content Type 167
  CA 15-3
  CA 27-29
  Immunohistochemical Test for Estrogen and Progesterone Receptors
Cancer Source
  Sex and Cancer: Questions for Your Doctor
  The Soy and Breast Cancer Controversy: Cause for Concern?
  The 'Chemobrain' Phenomenon in Breast Cancer
  MRIs for Breast Cancer Screening—Who Needs Them?
  Hormonal Therapy: Managing Side Effects in Women
  If You Are Having Hormonal Therapy
  What Is Breast Cancer?
  What to Know About Your Treatment Choices for Breast Cancer
  Ductal Carcinoma
  Statistics About Breast Cancer
  Can I Get Checked for Breast Cancer Before I Have Symptoms?
  What Can I Do if I Am at Risk for Breast Cancer?
  What Are the Symptoms of Breast Cancer?
  How Does My Doctor Know I Have Breast Cancer?
  Tests That Help Evaluate the Traits of Your Breast Cancer
  Understanding Your Grade and Stage of Breast Cancer
  What to Know About Surgery for Breast Cancer
  Breast Cancer: What Happens After Reconstructive Surgery
  Goal of Chemotherapy for Breast Cancer
  Do What You Can to Ease Side Effects of Treatment and Symptoms for Breast Cancer
  Finding Out You Have Breast Cancer
  What to Know About Combination Therapy for Breast Cancer
  How You Get Radiation for Breast Cancer
  What You Need to Know About Hormone Therapy for Breast Cancer
  Tips for Feeling Your Best During Treatment for Breast Cancer
  Taking Care of Your Incision After Breast Surgery
  How Your Doctor Uses Biopsies to Make Your Diagnosis of Breast Cancer
  Understanding Your Type of Breast Cancer
  What to Know About Inflammatory Breast Cancer (IBC)
  Can I Survive Breast Cancer? What Is My Prognosis?
  Am I at Risk for Breast Cancer?
  Myths About What Causes Breast Cancer
  Questions to Ask About Treatment for Breast Cancer
  What to Expect After Surgery for Breast Cancer
  What Happens During Radiation Therapy for Breast Cancer
  What to Expect After Radiation Treatment for Breast Cancer
  What Happens During Chemotherapy for Breast Cancer
  Making the Decision to Have Hormone Therapy for Breast Cancer
  What Happens During Hormone Therapy for Breast Cancer
  Ovarian Ablation as Hormone Therapy for Breast Cancer
  What to Expect After Taking Hormone Therapy Drugs for Breast Cancer
  What to Know About Targeted Therapy for Breast Cancer
  What Happens During Targeted Therapy for Breast Cancer
  Making the Decision to Have Breast Reconstruction After a Mastectomy for Breast Cancer
  When Breast Cancer Spreads to the Bones
  Exercising After Breast Cancer: Moving Toward Health
  Aromatase Inhibitors for Breast Cancer
Cancer FAQs
  Breast Cancer FAQ
NCI Patient Summary
  Breast Cancer Treatment and Pregnancy (PDQ®)
  Breast Cancer Quiz
  Breast Cancer Risk Assessment
Adult Diseases and Conditions
  Breast Cancer Prevention Trial (BCPT)
  Chemotherapy for Breast Cancer Treatment
  About Clinical Trials: Information from the National Cancer Institute
  How Is Breast Cancer Diagnosed?
  General Information About Breast Cancer
  Other Treatments for Breast Cancer
  National Surgical Adjuvant Breast and Bowel Project (NSABP)
  Radiation Therapy for Breast Cancer Treatment
  Risk Factors for Breast Cancer
  Signs and Symptoms of Breast Cancer
  Stages of Breast Cancer
  Study of Tamoxifen and Raloxifene (STAR)
  Breast Cancer Statistics
  About Taxol
  Breast Health: Three-Step Plan for Preventive Care
  Treatments for Breast Cancer
  Hereditary Breast Ovarian Cancer Syndrome (BRCA1/BRCA2)
  Genetics of Breast Cancer
  Breast Cancer Overview
  Should You Consider Preventive Drugs for Breast Cancer?
  Should You Be Tested for the Breast Cancer Gene?
Test and Procedures
  Breast Biopsy