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Ovarian Cancer and Breast Cancer: Understanding the Connection

Medically reviewed by Mark Levin, M.D.
Written by Maureen McNulty
Posted on January 27, 2022

Some people are more likely to be diagnosed with both breast cancer and ovarian cancer. Ovarian cancer includes tumors that start growing in the ovaries as well as cancer that develops in the fallopian tubes (the tubes that connect the ovaries to the uterus) or the peritoneum (the inner lining of the abdomen).

Some of the same risk factors can lead to both breast and ovarian cancers. Although certain risk factors can’t be controlled, there are things that a person with breast cancer can do to lower the risk of ovarian cancer.

What Causes Ovarian Cancer and Breast Cancer?

To understand why different kinds of cancer can develop within the same person, it helps to learn what causes cancer. Cancer forms when genes undergo changes and cause a cell to start behaving abnormally and grow out of control.

Some of these gene changes are inherited (passed down from parent to child). Inherited gene mutations are present at birth, and they can be found in every cell within the body. These types of mutations can sometimes lead to family cancer syndromes, in which several people within the same family develop cancer.

Acquired gene changes happen as a result of environmental or lifestyle factors. These gene mutations occur during a person’s lifetime and are found only in some cells. Most cancer is caused by acquired gene changes and does not run in families.

Inherited and acquired mutations can cause cells to begin growing abnormally. Many of these gene changes can increase a person’s risk for developing one or more types of cancer.

Inherited Factors That Lead to Ovarian and Breast Cancer

Breast cancer is sometimes linked to changes in the BRCA1 and BRCA2 genes. These genes are normally responsible for healing cells when they become damaged. BRCA genes help prevent cells from turning cancerous. However, when cells have mutated BRCA genes, damage cannot be easily fixed and cells may begin growing out of control, forming a tumor.

Changes in the BRCA genes lead to a family cancer syndrome called hereditary breast and ovarian cancer syndrome (HBOC). People with this condition are more likely to have a family history of breast cancer or ovarian cancer. They also have a high risk of being diagnosed with multiple cancers or being diagnosed with cancer at a young age. HBOC increases the risk of several different cancer types, including pancreatic cancer, prostate cancer in men, and melanoma. However, BRCA gene mutations most often lead to breast and ovarian cancers:

  • About 1.6 percent of women without BRCA mutations develop ovarian cancer at some point in their lives.
  • The estimated risk of breast cancer in women with a BRCA mutation is 45 percent to 85 percent by age 70 years.
  • Around 13 percent of women without BRCA mutations are diagnosed with breast cancer over a lifetime.
  • BRCA1 mutations lead to a 55 percent to 72 percent risk of breast cancer. The lifetime risk for women with BRCA2 gene mutations is 45 percent to 69 percent.

HBOC is usually caused by BRCA mutations. However, other family cancer syndromes that increase the risk of ovarian and breast cancer can also be caused by inherited changes in other genes. Affected genes include TP53, PTEN, ATM, and CHEK2.

If your breast cancer was caused by inherited changes in BRCA1, BRCA2, or another gene, you may also have an increased risk of developing ovarian cancer. However, if you developed breast cancer because of other factors, your risk of ovarian cancer may not be raised. Genetic testing can help you find out if you have an inherited gene mutation.

Environmental and Lifestyle Risk Factors

Acquired gene changes may develop after exposure to substances that damage DNA, like ultraviolet light or radiation. Some environmental and lifestyle factors can increase the chances that genes mutate and change. These factors make people more likely to be diagnosed with multiple types of cancer. Gene changes may also develop randomly as a cell grows and divides.

Factors that raise the risk of ovarian cancer or breast cancer include:

  • Older age
  • Heavier body weight
  • Never having had children
  • Having your first child at a later age (older than 35 years old for ovarian cancer or older than 30 years old for breast cancer)
  • Using hormone replacement therapy (HRT) during or after menopause

If you have any of these shared risk factors, you are slightly more likely to develop ovarian cancer and breast cancer.

Lowering Risk of Ovarian Cancer

People with breast cancer who are concerned about their ovarian cancer risk should talk to their doctor to learn more about potential next steps. You may be able to change certain habits in order to lower your risk of developing ovarian cancer in the future. Additionally, you may be a candidate for genetic testing to determine whether you have any inherited gene changes.

Lowering Your Risk Using Lifestyle Changes

Ovarian cancer is most often caused by environmental and lifestyle factors. Some risk factors, such as growing older, can’t be changed. You can have more influence over other factors. Preventive strategies to reduce ovarian cancer risk include:

  • Eat a balanced diet
  • Get more physical activity
  • Achieve and maintain a healthy weight
  • Quit smoking
  • If you give birth, try breastfeeding
  • Don’t use HRT after going through menopause
  • Undergo a hysterectomy (surgery to remove the uterus) or a bilateral salpingo-oophorectomy (surgery to remove the ovaries and fallopian tubes)

People who take birth control pills, also called oral contraceptives, have a 50 percent lower risk of developing ovarian cancer. This may be a good risk-reducing strategy for women who have inherited BRCA gene mutations. However, birth control pills can increase the risk of developing breast cancer, so doctors may not recommend this strategy for women with a history of breast cancer.

Genetic Testing and Ovarian Cancer

Just 3 percent of people with breast cancer have inherited mutations in BRCA genes. This means that most people diagnosed with breast cancer don’t have a gene change that puts them at risk for ovarian cancer. However, you may be more likely to have one of these inherited mutations if you were diagnosed with breast cancer before the age of 50, developed breast cancer in both breasts, or have multiple family members — including male family members — who were diagnosed with breast cancer.

If your doctor thinks you may have a genetic mutation that leads to a higher risk of cancer, they may recommend genetic counseling and genetic testing. In this case, you will meet with a genetic counselor to talk about your cancer risk, and you may undergo tests that help determine whether you have certain gene changes. These tests are very simple and involve either a blood or saliva test. When one person within a family finds out they have an inherited gene change, other family members should be informed and may also want to be tested to determine their risk levels.

Ovarian Cancer Screening

Mammograms are recommended as a regular screening tool to help detect breast cancer. However, current screening tests for ovarian cancer aren’t as effective.

Researchers have studied two possible ovarian cancer screening tests. One test measures levels of CA-125 in the blood. Levels of this molecule are often raised in people with ovarian cancer. However, older age or other benign (noncancerous) conditions may also lead to high CA-125 levels. Another possible screening tool is a transvaginal ultrasound, a test that provides an image of the organs inside the pelvis. An ultrasound can detect masses on the ovary, but these are usually benign.

Studies have found that CA-125 and transvaginal ultrasound screenings don’t reduce ovarian cancer death rates. Additionally, they sometimes require women to undergo unnecessary further testing or surgery. For this reason, most experts don’t recommend using these tests to screen for ovarian cancer in the general population. However, some doctors may use these tests to screen for cancer in women with inherited gene changes that could lead to ovarian cancer.

Knowing the Symptoms of Ovarian Cancer

When ovarian cancer is caught early, it leads to better outcomes. Looking out for ovarian cancer symptoms may help you detect cancer at a stage when it is more easily treated. Symptoms include:

  • Pain in the abdomen, pelvis, or back
  • Abdominal bloating or swelling
  • Nausea
  • Feeling full after eating only a small amount
  • Constipation
  • Tiredness
  • Changes in your menstrual period
  • Changes in vaginal discharge
  • Needing to urinate often
  • Pain during intercourse

These symptoms can also be caused by other health conditions besides cancer. However, if you notice any changes or if you feel different than normal, talk to your health care provider.

Talk With Others Who Understand

MyBCTeam is the social network for people with breast cancer. On MyBCTeam, more than 54,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Are you living with ovarian cancer or breast cancer? Share your experiences in the comments below, or start a conversation by posting on your Activities page.

Posted on January 27, 2022
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Mark Levin, M.D. is a hematology and oncology specialist with over 37 years of experience in internal medicine. Review provided by VeriMed Healthcare Network. Learn more about him here.
Maureen McNulty studied molecular genetics and English at Ohio State University. Learn more about her here.

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