Including Risk of Common Genetic Variants May Lead to Better Estimates of Breast and Prostate Cancer Risk in Men With BRCA1/2 Mutations
Researchers combined the risk of common genetic variants associated with breast and prostate cancer to better estimate breast and prostate cancer risk in men with BRCA1/2 mutations.
Breast cancer in men is rare, but it does happen. Fewer than 1% of all breast cancers occur in men. For men, the average lifetime risk of being diagnosed with breast cancer is about 1 in 1,000.
Like women, men can have mutations in the BRCA1 and BRCA2 genes.
Everyone has BRCA1 and BRCA2 genes. The function of the BRCA genes is to repair cell damage and keep breast, ovarian, and other cells growing normally. But when these genes contain abnormalities or mutations that are passed from generation to generation, the genes don't function normally and breast, ovarian, prostate, and other cancer risk increases.
Men who have an abnormal BRCA2 gene have a higher risk of breast cancer than men who don't -- about 8% by the time they're 80 years old. This is about 8 times greater than average.
Men with an abnormal BRCA1 gene have a slightly higher risk of prostate cancer. Men with an abnormal BRCA2 gene are 7 times more likely than men without the abnormal gene to develop prostate cancer. Other cancer risks, such as cancer of the skin or digestive tract, also may be slightly higher in men with mutated BRCA1 or BRCA2 genes.
Researchers know that other genetic variants, called single nucleotide polymorphisms (SNPs), also are linked to breast and prostate cancer. Still, each SNP contributes only a tiny amount to a person’s overall risk of developing cancer.
SNPs are the most common type of genetic variant. Each SNP is a difference in a single building block of DNA (called a nucleotide). SNPs happen normally in our DNA -- scientists estimate that an SNP happens once in every 300 nucleotides, which means there are about 10 million SNPs in the human genome. Most SNPs have no effect on health or development, but some, like the ones associated with breast and prostate cancer, may have health implications.
More than 100 SNPs are associated with prostate cancer in men and breast cancer in women. So far, only two SNPs have been linked to breast cancer in men, but there is some evidence suggesting that the SNPs associated with breast cancer in women may affect the risk of breast cancer risk in men.
A study combined the risk of 102 SNPs associated with breast cancer and 103 SNPs associated with prostate cancer into a single risk factor, called a polygenic risk score, to better estimate breast and prostate cancer risk in men with a BRCA1 or BRCA2 mutation.
The research was published in the July 10, 2017 issue of the Journal of Clinical Oncology. Read “Prediction of Breast and Prostate Cancer Risks in Male BRCA1 and BRCA2 Mutation Carriers Using Polygenic Risk Scores.”
In the study, the researchers essentially added up the information on 102 SNPs associated with breast cancer and 103 SNPs associated with prostate cancer in 277 men diagnosed with breast cancer, 212 men diagnosed with prostate cancer, and 1,313 men who hadn’t been diagnosed with either cancer. All the men in the study had a BRCA1 or BRCA2 mutation.
The researchers found that 68 of the SNPs associated with breast cancer in women seemed to increase the risk of the disease in men by about the same amount they do in women.
Men with the highest breast cancer polygenic risk scores were about 2.4 times more likely to be diagnosed with breast cancer than men with the lowest polygenic risk scores.
Similarly, men with the highest prostate cancer polygenic risk scores were about 3.5 times more likely to be diagnosed with breast cancer than men with the lowest polygenic risk scores.
The researchers also estimated the risks of breast and prostate cancer in men by age based on their polygenic risk scores:
- Men with a BRCA2 mutation with the lowest polygenic risk scores had about a 5% risk of breast cancer by age 80; men with the highest polygenic risk scores had about a 14% risk.
- Men with a BRCA1 mutation with the lowest polygenic risk scores had about a 7% risk of prostate cancer by age 80; men with the highest polygenic risk scores had about a 26% risk.
- Men with a BRCA2 mutation with the lowest polygenic risk scores had about a 19% risk of prostate cancer by age 80; men with the highest polygenic risk scores had about a 61% risk.
The researchers said that while there are no screening or preventive strategies for breast cancer for men with a BRCA1 or BRCA2 mutation, recommendations do include:
- education about risk
- regular breast exams by a doctor
- prostate cancer screening
It’s hoped that the results of this study may be used to develop personalized strategies for men to manage higher-than-average risks of breast and prostate cancer.
If you’re a man and know you have a BRCA1 or BRCA2 mutation, it makes sense to do all that you can do to keep your risk of breast and prostate cancer as low as it can be. While there are no established risk-reducing strategies for men like there are for women, such as preventive surgery or taking hormonal therapy medicine preventively, you can:
- Talk to your doctor about developing a regular, comprehensive screening plan that makes the most sense for your unique situation, age, and family history.
- Maintain a healthy weight by eating a diet full of vegetables and unprocessed food and limiting sugar, trans fats, and processed foods.
- Exercise regularly at a moderate or vigorous level.
- Avoid or limit alcohol.
- Never smoke or quit if you do smoke.
— Last updated on July 31, 2022, 10:46 PM
Share your feedback
Help us learn how we can improve our research news coverage.
Was this article helpful?