For women with breast cancer considering prophylactic mastectomy

Prophylactic mastectomy is a surgery to remove one or both breasts; prophylactic meaning a preventative measure, done in hopes of reducing your risk of breast cancer. Bilateral prophylactic mastectomies, or double mastectomies, are the removal of both breasts.

For breast cancer patients, the average lifetime risk of developing a new breast cancer in the opposite breast is low, ranging from 4 to 8%, and is even lower in patients who receive chemotherapy or hormone therapy as part of their treatment. It is also important to be aware that while removing the opposite breast reduces the risk of developing a new cancer, it does not change the outcome from the existing cancer. For the majority of women, removing the opposite breast is not necessary. However, there are some women who may be at higher risk, and your doctor can help you determine your level of risk and decide on the right course for you.

Is a preventative double mastectomy for me?

A woman newly diagnosed with breast cancer will often say, when discussing her surgical options, “Why not just take them both off?” These patients often express a desire to “never have to worry about my breasts again,” particularly those women who have had difficulty with screening procedures in the past or have a history of multiple breast biopsies. Women in whom the primary cancer was initially missed often lose faith in mammography and other screening methods and may feel that the only way to be sure this will not happen to them in the future is to remove both breasts.

Double mastectomies have been featured more in the mainstream media, increasing awareness of this option. Furthermore, the option of immediate reconstruction serves to make this route more appealing than in the past. But what is the real risk of developing a new cancer in the other breast? Do double mastectomies really save lives or improve quality of life? The answer is different for every woman. This article seeks to address these issues and assist individuals in making the most informed decision.

After surviving breast cancer, what are my chances of getting cancer in the other breast?

There are a number of a large studies with ten-year follow up or more that have estimated that the risk of getting cancer in the other breast increases 0.2 to 0.4% per year. Therefore if a cancer survivor lives another 20 years after her diagnosis, her risk of developing a breast cancer on the opposite side ranges from 4 to 8%. The risk is lower if she has chemotherapy or hormone therapy as part of her original treatment (0.1 to 0.2%), which translates to a 2 to 4% 20-year risk. These figures represent the average risk of developing contralateral breast cancer (that is, cancer in the opposite breast) in the future. Some women are at higher risk based on their age or the characteristics of their tumor.

Those at higher risk include:

  1. Women with estrogen receptor negative tumors. These are cancers that are not sensitive to the effects of estrogen and are less common (25% of breast cancers). This information can usually be obtained at the time of the initial biopsy. The risk is estimated at 0.2 to 0.65% per year, or up to a 12% 20-year risk. This risk can be decreased if the patient is treated with chemotherapy.
  2. Women who are younger (age less than 50 years) at diagnosis. Not only do these women have a longer natural life span, and therefore a longer time to develop a new breast cancer, but studies show that their yearly risk is also higher on average. Their opposite breast cancer risk is about 11% at 20 years.
  3. Women with known genetic changes (mutations) that predispose them toward developing cancer. These include mutations in the BRCA1 and 2 genes, p53 gene, and other known rare genes for which genetic testing is available. (See below)
  4. Women with a history of prior radiation to the chest, such as for treatment of lymphoma.

I have cancer in my family – how does that affect my risk of getting breast cancer a second time?

Hereditary breast cancer

About 5 to 10% of all breast cancer cases in the United States are hereditary, meaning that they occur as a result of a known inherited genetic defect. The most common genetic defect found in hereditary breast cancer is the BRCA gene mutation, which carries a very high lifetime risk of breast cancer, between 45 to 87%. Women considered at risk for having these mutations include those who develop breast cancer at a young age (less than 50 years), those with breast cancer who have two close relatives on the same side of the family with breast or ovarian cancer and those who have a male relative with breast cancer. Any patient with suggestive personal or family history should be considered for genetic counseling and possibly testing. The risk of developing a second breast cancer on the opposite breast for patients who test positive for the BRCA mutation is approximately 3% per year, or 60% in 20 years, and many of these women do opt for preventive mastectomy.

Familial breast cancer

Although most women with breast cancer do not have one of these known gene mutations, women with a positive family history do find themselves at increased risk for developing a second cancer. The degree of risk depends on how strong the family history is. At highest risk are women who have a first-degree relative (parent, sibling, or offspring) with early onset breast or ovarian cancer (younger than 50 years), or a person who has either a first- AND second-degree relative or multiple first-degree relatives with breast or ovarian cancer. A second-degree relative is a grandparent, aunt, niece, or grandchild. These women have been found to have about a two- to threefold increased chance of developing a new cancer on the other side. Women who only have a third-degree relative with breast cancer, such as a great grandparent or cousin, have only a very slightly increased risk of developing new breast cancer on the other side, about 1.5 times the average person's risk. It is unclear to what extent other types of cancer in the family affect a woman’s breast cancer risk, but it does seem to be much less significant, in general. A genetic counselor can be very helpful in determining one’s level of risk based on family history.

Patient Characteristic Annual Risk 20 Year Risk
Average Risk 0.2-0.4% 4-8%
After chemotherapy/endocrine therapy 0.1-0.2% 2-4%
Age less than 50 years 0.3-0.6% 6-12%
Estrogen receptor negative 0.2-0.65% 4-13%
Moderate family history of breast cancer 0.3-0.6% 6-12%
Strong family history of breast cancer 0.4-1.2% 8-24%
BRCA gene mutation 3% 60%

What are the downsides to a preventive double mastectomy?

A double mastectomy is a more complex operation than simply removing the lump in one breast, especially if reconstruction is involved. Sometimes multiple operations are required. The complication rates from these procedures range from 16 to 37%. Although most women who opt to remove both breasts during breast cancer treatment state that they have increased peace of mind after surgery, studies show that about 10% say that they regret the decision. Adverse effects on sexual relationships and feelings of femininity were noted in 20 to 30% of patients, and 15 to 20% state they are less than satisfied with the final cosmetic result. Post reconstruction pain also can be seen as far out as three years after surgery and has been noted to afflict up to 40% of patients, affecting daily activities for some.

Another concern is that, except in the highest risk women, removing the opposite breast has not been shown to help patients live longer. In other words, even if it does prevent a second cancer in a small percentage of women, most of those women would not have died from their second cancer anyway. The effect that breast cancer has on survival is usually from the patient’s original cancer. Additionally, it is important to note that while removing the opposite breast significantly reduces the risk of getting cancer on that side, it does not eliminate the risk completely. There remains a 5 to 8% risk of cancer developing in the remaining skin.

Last reviewed: 
August 2017

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