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Family History of Prostate Cancer Seems to Increase Breast Cancer Risk

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About 5% to 10% of breast cancers are thought to be hereditary, caused by abnormal genes passed from parent to child.

Genes are particles in cells, contained in chromosomes, made of DNA (deoxyribonucleic acid). DNA contains the instructions for building proteins. And proteins control the structure and function of all the cells that make up your body.

Think of your genes as an instruction manual for cell growth and function. Abnormalities in the DNA are like typographical errors. They may provide the wrong set of instructions, leading to faulty cell growth or function. In any one person, if there is an error in a gene, that same mistake will appear in all the cells that contain the same gene. This is like having an instruction manual in which all the copies have the same typographical error.

A study suggests that women with first-degree relatives (father, brother, son) who have been diagnosed with prostate cancer probably have a higher risk of breast cancer.

The research was published online on March 9, 2015 by the journal Cancer. Read the abstract of “Familial clustering of breast and prostate cancer and risk of postmenopausal breast cancer in the Women’s Health Initiative Study.”

The research is part of the very large Women’s Health Initiative Clinical Trial and the Women’s Health Initiative Observational Study. Both studies are commonly called the WHI. Together, the two studies include information from more than 161,600 postmenopausal women who were ages 50 to 79 when they joined the study between 1993 and 1998. The WHI is looking for links between health, diet, lifestyle, and genetic factors and health problems, such as cancer.

In this study, the researchers looked at the records of 78,171 women in the WHI Observational Study who had never been diagnosed with breast cancer when they enrolled in the study. By 2009, 3,506 breast cancers had been diagnosed in the women.

The researchers looked to see how many of the women’s first-degree relatives (fathers, mothers, sisters, brothers, sons, and daughters) had been diagnosed with either breast or prostate cancer.

The results showed:

  • breast cancer risk was 14% higher than average in women with a first-degree relative who had been diagnosed with prostate cancer
  • breast cancer risk was 78% higher than average in women with first-degree relatives who had been diagnosed with breast and prostate cancer

The risk of breast cancer was much higher -- more than double the average risk -- in Black women with a first-degree family history of both breast and prostate cancer compared to white women (66% higher) with a first-degree family history of breast and prostate cancer.

The researchers said the results suggest that doctors should take a complete family history of all cancers -- even cancers in family members of the opposite sex -- to help estimate a woman’s risk of breast cancer.

“These findings are important in that they can be used to support an approach by clinicians to collect a complete family history of all cancers -- particularly among first-degree relatives -- in order to assess patient risk for developing cancer,” said Jennifer Beebe-Dimmer, Ph.D., M.P.H. of the Barbara Ann Karmanos Cancer Institute and Wayne State University, who was the lead researcher. “Families with clustering of different tumors may be particularly important to study in order to discover new genetic mutations to explain this clustering.”

You can’t change your genes or your family history. But you can take steps to keep your risk of breast cancer as low as it can be.

If your mother, father, sister, brother, or children have been diagnosed with breast or prostate cancer, it’s a good idea to tell your doctor about these diagnoses. It’s also a good idea to share the information with these family members so everyone has an accurate estimate of his or her cancer risk.

There are also lifestyle choices that you may want to make, including:

  • maintaining a healthy weight
  • exercising every day
  • limiting or avoiding alcohol
  • eating a healthy diet that’s low in processed foods, sugar, and trans fats
  • not smoking

To learn more about breast cancer risk and other options to keep your risk as low as it can be, visit the Lower Your Risk section.

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