What is bilateral breast cancer?

When breast cancer develops in both breasts, it’s called bilateral breast cancer. This accounts for 1.4% to 11% of all breast cancer diagnoses, according to the National Institutes of Health.

Bilateral breast cancer is not as common as unilateral breast cancer (breast cancer in just one breast). As with all types of breast cancer, the chances of successful treatment are higher when bilateral breast cancer is caught early. So, it’s important to know the symptoms and risk factors.

To learn more about bilateral breast cancer, we spoke with Banu Arun,M.D., breast medical oncologist and co-medical director of UT MD Anderson’s Clinical Cancer Genetics Program. Here’s what she shared.

Types of bilateral breast cancer

Bilateral breast cancer – sometimes called contralateral breast cancer – is categorized based on when the second tumor develops.

Synchronous bilateral breast cancer

Tumors are diagnosed in both breasts around the same time. This is usually defined as within six to 12 months of each other.

Asynchronous bilateral breast cancer

Asynchronous bilateral breast cancer, also called metachronous bilateral breast cancer, occurs when a second primary breast cancer develops in the other breast more than 12 months after the first breast cancer diagnosis. It is slightly more common than synchronous bilateral breast cancer.

Risk factors for bilateral breast cancer

Certain factors put you at a higher risk for developing bilateral breast cancer. The most common risk factors are:

• Inherited genetic mutations, such as BRCA1 and BRCA2
• Being diagnosed with breast cancer at a young age
• Family history of breast cancer   

Symptoms of bilateral breast cancer

Bilateral breast cancer symptoms are usually the same as symptoms for other types of breast cancer. Symptoms may include:

• A lump or mass in the breast
• Breast skin changes, like redness, dimpling or thickening of the skin that feels like the texture of an orange peel
• Inverted nipples
• Nipple discharge
• Swelling in the breast

Sometimes bilateral breast cancer doesn’t cause any symptoms, and a tumor is found through imaging.

How bilateral breast cancer is diagnosed

If you have symptoms, your doctor might perform or order any of the following to help diagnose bilateral breast cancer:

• Breast exam: During a clinical breast exam, a clinician will visually inspect your breasts as well as use their hands to feel for any masses or abnormalities.
• Diagnostic mammogram: A diagnostic mammogram is done to further examine a specific area of the breast for abnormalities.
• Breast ultrasound or MRI: A breast ultrasound or breast MRI uses sound waves or magnet and radio waves, respectively, to produce detailed images of your breast.
• Breast biopsy: If your doctor suspects cancer, they will order a breast biopsy. This is when a sample of your breast tissue is examined under a microscope. It’s the only test that can diagnose breast cancer. If breast cancer is found, you may need additional tests, like a sentinel lymph node biopsy, to show if the cancer has spread to nearby lymph nodes or other parts of your body.

Regular screening mammograms can also help detect bilateral breast cancer if you do not have any symptoms. If you get an abnormal result from a screening mammogram, your doctor will want to run more tests to help determine the cause of the abnormality.

Treatment for bilateral breast cancer

We approach treatment for bilateral breast cancer the same way we do for cancer that is just in one breast. Your care team will discuss the best treatment plan based on several factors, including:

• Your age
• The size and location of the tumor
• The tumor’s biomarkers (e.g., HER2)

You may have any of the following treatment options.

Mastectomy

A partial or segmental mastectomy involves removing the tumor and surrounding breast tissue. This can be done in both breasts. A bilateral mastectomy, also called a double mastectomy, is removal of both breasts. Your doctor may recommend a bilateral mastectomy for larger tumors or if you have a genetic mutation like BRCA1 or BRCA2.

Chemotherapy

You may be given chemotherapy before surgery to shrink the tumor or after surgery to lower the risk of recurrence.

Radiation therapy

Radiation therapy uses powerful beams of energy to kill breast cancer cells. It may be given before surgery to help shrink tumors or after surgery to kill any remaining microscopic cancer cells.

Targeted therapy

Targeted therapy is treatment that slows or stops the growth of breast cancer by targeting the proteins that produce them. Targeted therapy is used to treat HER2 positive breast cancer.

Hormone therapy

Hormone therapy is used to treat breast cancers that are positive for the hormone receptors estrogen and progesterone. It can be given before surgery to shrink the tumor or after surgery for several years to help prevent recurrence.

Bilateral breast cancer is not the same as metastatic breast cancer

Bilateral breast cancer means you have two different breast tumors – one in each breast. Each diagnosis is staged and treated as a separate cancer.

Metastatic breast cancer describes a primary breast cancer that has spread far away from the original tumor’s location. It is also known as stage 4 breast cancer.

While it is possible, having breast cancer metastasize to the opposite breast is very rare.

Breast cancers most likely to be bilateral

Invasive lobular carcinoma is a type of breast cancer that is most likely to affect both breasts.   

Certain factors can play a role in whether breast cancer is bilateral as well. For example, patients with ER positive breast cancer are often given the hormone therapy drugs tamoxifen or anastrozole. These drugs reduce the risk of developing new cancers in the opposite breast. So, if someone with ER positive breast cancer does not receive this treatment, the risk of developing another ER-positive breast cancer in the opposite breast is more likely.

Some data suggests that triple-negative breast cancer has a higher chance of being bilateral, but triple-negative breast cancer is also tied to having an inherited BRCA 1 genetic mutation. So, the risk factors for triple-negative breast cancer and bilateral breast cancer overlap.  

Prognosis for bilateral breast cancer

The prognosis for bilateral breast cancer is the same as unilateral breast cancer. It depends on several factors, including the type of breast cancer, the cancer’s stage and its hormone receptor status.

Just like unilateral breast cancer, bilateral breast cancer can be aggressive. How aggressive the cancer is depends on several factors, including the cancer’s stage, the type of tumor and its hormone receptor status. Aggressive breast cancer often grows and spreads quickly and is more likely to come back.     

The five-year survival rate for breast cancer is 90%. But keep in mind these are just estimates. Your doctor can provide you with specific information about your outlook.

Why breast cancer screening is important

The chance for successful treatment is higher when bilateral breast cancer is caught early. If you’re diagnosed with breast cancer, you have a 0.5% to 1% chance of developing a new breast cancer in the opposite breast. And you may not have symptoms. That’s why regular breast cancer screenings are so important.

Women 25 years and older should ask their doctor for a breast cancer risk assessment and get a clinical breast exam every one to three years. Women of average risk should begin getting an annual mammogram and clinical breast exam at 40 years old. If you are at an increased risk for breast cancer, your doctor will recommend a personalized screening plan.

You should be aware of how your breasts look and feel, and you should see your doctor if you notice any changes or abnormalities.

If you are a patient at UT MD Anderson diagnosed with bilateral breast cancer, you can ask for a referral to our High Risk Breast Screening and Genetics Clinic. We have a multidisciplinary team of specialists who are here to help you.  

Request an appointment at UT MD Anderson online or call 1-877-632-6789.